clang-format: [JS] sort ES6 imports.

[mprobst]

Summary

This change automatically sorts ES6 imports and exports into four groups:
absolute imports, parent imports, relative imports, and then exports. Exports
are sorted in the same order, but not grouped further.

[djasper]

Just two high-level comments. Will review in more depth later.

include/clang/Format/Format.h

770 ↗

(On Diff #57009)

Why is this a separate function as opposed to looking at Style.Language?

lib/Format/Format.cpp

1140

I know this file is already a huge mess, but can you move all of the JS import sorting stuff to a separate file?

[mprobst]

• extract TokenAnalyzer.h and SortJavaScriptImports.h/cpp
• clean up imports

[mprobst]

• extract TokenAnalyzer.h and SortJavaScriptImports.h/cpp
• clean up imports/
• includes

[djasper]

lib/Format/Format.cpp

23

Use clang-format to fix the order :-)

lib/Format/FormatTokenLexer.h

29

I believe it is a bit harmful to have that much code in a header. It now gets pulled into multiple translation units and is thus compiled multiple times only for the linker to deduplicate it afterwards. We should move the implementation in FormatTokenLexer.cpp. I am happy to do that as a follow up, though.

lib/Format/SortJavaScriptImports.cpp

55

This comment doesn't really explain what it is and it is not obvious to me.

113

No braces.

151

Add:

// FIXME: Pull this into a common function.

163

Is there any chance you are changing the total length of an import block?

227

No braces.

292

s/TODO(martinprobst)/FIXME/

Also, I'd probably remove the parameter until this is supported. This FIXME is quite hidden but if there is no Cursor in the interface, there is no confusion.

lib/Format/TokenAnalyzer.h

2

This isn't quite as bad as the other, but we probably want a dedicated .cpp file, too.

[mprobst]

• extract TokenAnalyzer.h and SortJavaScriptImports.h/cpp
• clean up imports/
• includes
• address review comments
• pull out implementations from header files.

[mprobst]

PTAL.

lib/Format/SortJavaScriptImports.cpp

163

No, this only ever monotonously increases the length. I'm aware things fall apart if it doesn't ;-)

227

Just can't get used to that, it feels so wrong...

[mprobst]

• extract TokenAnalyzer.h and SortJavaScriptImports.h/cpp
• clean up imports/
• includes
• address review comments
• pull out implementations from header files.
• support side effect imports, keep in relative order at top.

[djasper]

I think, this looks good.

Manuel: Are you fine with this, design-wise?

lib/Format/SortJavaScriptImports.cpp

78

NB?

256

We probably should really have a variant of AnnotatedLine::startsWith() that can start at an arbitrary token. But we can try that in a follow-up.

[mprobst]

• extract TokenAnalyzer.h and SortJavaScriptImports.h/cpp
• clean up imports/
• includes
• address review comments
• pull out implementations from header files.
• support side effect imports, keep in relative order at top.
• Move getLanguageName to Format.h

[mprobst]

lib/Format/SortJavaScriptImports.cpp

78

"Nota bene". Seems to be uncommon in this code base, so removed.

256

Maybe that should be a function on FormatToken itself, that searches the linked list rooted at it?

Current->startsSequence(tok::star, Keywords.kw_as, tok::identifier)?

I'll take a stab at that.

[mprobst]

• review comments

[klimek]

include/clang/Format/Format.h

855 ↗

(On Diff #57440)

s/for debugging/.
Or do you want to claim that we'll arbitrarily change the strings here?

lib/Format/Format.cpp

1217–1225

I'd make this symmetric by pulling out 2 functions instead of falling through into the function.

lib/Format/SortJavaScriptImports.cpp

46

As not all of the members will be default initialized I'd prefer to have constructors.

46–47

This is really weird - a class called ImportExport that then has a bool IsExport. Please explain in a comment why you're doing that instead of any of:
a) managing a set of imports and exports on their own
b) calling this something else
c) having a class hierarchy

116

When I see ImpExp I think "ImplicitExpression". I'd name this ImportExport.
Also, it seems like we now have an uninitialized bool and enum in the struct.

164

If that's the case, please add a comment to that end.

208

Usually we call Lexer::getSourceText for that (don't we have a Lexer?)

253–254

This function is really long - can we perhaps break out smaller syntactic options.

259

Please don't put side-effects into an if (). This might be generally easier to read if nextToken() can't fail, and instead creates an invalid token.

[mprobst]

• address review comments

[mprobst]

PTAL.

lib/Format/SortJavaScriptImports.cpp

46–47

Discussed offline. I stand by this code. Yes, it has an odd boolean flag, but imports and exports in ES6 are essentially the same syntactical construct, with exports being syntactic sugar for import followed by export.

I've updated the comment on this struct substantially to explain that (I can tell how it's non-obvious).

Note that the boolean is never dispatched on in this code, except for the "empty line before exports" part. Exports are the same as imports wrt sorting them here.

116

Now called Reference.

208

We don't, FormatTokenLexer doesn't expose the Lexer, and TokenAnalyzer doesn't export FormatTokenLexer.

259

Done, much cleaner indeed. LLVM style guide says not to introduce new static globals with constructors, so I'm just using a field. Please advise if there's a better way.

[klimek]

lib/Format/SortJavaScriptImports.cpp

47–48

Thanks, this is much better.

85–86

Any reason you're not using a SourceRange?

94–97

Doesn't that break strict weak ordering requirements?

x = non-side-effect (url: a)
y = side-effect (url: b)
z = non-side-effect (url: c)
now x and y are incomparable:
!(x < y) because x.url < y.url
&& !(y < x) because of y == side-effect
but x and z are comparable:
x < z
breaks transitivity of incomparability (https://en.wikipedia.org/wiki/Weak_ordering#Strict_weak_orderings)

To keep them equal, wouldn't you need:

if (LHS == SIDE_EFFECT && RHS == SIDE_EFFECT)
  return false;

(that would at least seem symmetric)

129

It seems like you can pull the loop below into its own function parseModuleReferences or something.

130

LastStart is just the start of the currently processed module reference, right? I'd just call it Start then.

136

Why are you defining this here, far before its use?

I think this code might be slightly simpler (for me to understand) if you just pulled Reference out of the loop, and got rid of LastStart.

[mprobst]

PTAL.

lib/Format/SortJavaScriptImports.cpp

94–97

As discussed offline, the comparison before makes sure that RHS == SIDE_EFFECT here.

Added a comment.

136

As discussed offline, moved the declaration a bit down.

I think exposing just a SourceLocation Start makes the algorithm easier to read, otherwise it'd look like a whole JsModuleReference could leave the loop, which is never the case. It explicitly points out we only have state outside of the loop to track the start.

[mprobst]

• address review comments
• - extract parseModuleReferences

[mprobst]

PTAL.

[klimek]

We're getting there. Couple of nits left.

lib/Format/SortJavaScriptImports.cpp

95–98

Yea, completely missed that the != above.

129

Return by value.

217–218

Both of these are used only once, perhaps inline?

230

I'd put that down after References.push_back so calculating the Reference is at least a single flow.

[mprobst]

lib/Format/SortJavaScriptImports.cpp

217–218

These are setting fields for the parse state (note: this is not a variable declaration).

[mprobst]

• address review comments
• - extract parseModuleReferences
• more review comments

[klimek]

lg

[mprobst]

• correctly insert breaks after import block

[mprobst]

• ranges

[klimek]

lib/Format/SortJavaScriptImports.cpp

161

Between categories of imports and imports and exports, right?

171–172

Shouldn't we add 2 if NewlinesBefore is 0? Or is that syntactically impossible?

[mprobst]

Thanks for the review, appreciated!

lib/Format/SortJavaScriptImports.cpp

161

Added a comment.

171–172

The next token is on a new line, so it gets a wrap just from that already. I've added a test though.

lib/Format/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS support)
 
 add_clang_library(clangFormat
   AffectedRangeManager.cpp
   BreakableToken.cpp
   ContinuationIndenter.cpp
   Format.cpp
   FormatToken.cpp
+  FormatTokenLexer.cpp
+  SortJavaScriptImports.cpp
+  TokenAnalyzer.cpp
   TokenAnnotator.cpp
   UnwrappedLineFormatter.cpp
   UnwrappedLineParser.cpp
   WhitespaceManager.cpp
 
   LINK_LIBS
   clangBasic
   clangLex
   clangToolingCore
   )

lib/Format/Format.cpp

 /// \brief This file implements functions declared in Format.h. This will be
 /// split into separate files as we go.
 ///
 //===----------------------------------------------------------------------===//
 
 #include "clang/Format/Format.h"
 #include "AffectedRangeManager.h"
 #include "ContinuationIndenter.h"
+#include "FormatTokenLexer.h"
+#include "SortJavaScriptImports.h"
+#include "TokenAnalyzer.h"
 #include "TokenAnnotator.h"
 #include "UnwrappedLineFormatter.h"
 #include "UnwrappedLineParser.h"
 #include "WhitespaceManager.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/DiagnosticOptions.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/VirtualFileSystem.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/STLExtras.h"
std::string configurationAsText(const FormatStyle &Style) {
   // reference here.
   FormatStyle NonConstStyle = expandPresets(Style);
   Output << NonConstStyle;
   return Stream.str();
 }
 
 namespace {
 
-class FormatTokenLexer {
-public:
-  FormatTokenLexer(const SourceManager &SourceMgr, FileID ID,
-                   const FormatStyle &Style, encoding::Encoding Encoding)
-      : FormatTok(nullptr), IsFirstToken(true), GreaterStashed(false),
-        LessStashed(false), Column(0), TrailingWhitespace(0),
-        SourceMgr(SourceMgr), ID(ID), Style(Style),
-        IdentTable(getFormattingLangOpts(Style)), Keywords(IdentTable),
-        Encoding(Encoding), FirstInLineIndex(0), FormattingDisabled(false),
-        MacroBlockBeginRegex(Style.MacroBlockBegin),
-        MacroBlockEndRegex(Style.MacroBlockEnd) {
-    Lex.reset(new Lexer(ID, SourceMgr.getBuffer(ID), SourceMgr,
-                        getFormattingLangOpts(Style)));
-    Lex->SetKeepWhitespaceMode(true);
-
-    for (const std::string &ForEachMacro : Style.ForEachMacros)
-      ForEachMacros.push_back(&IdentTable.get(ForEachMacro));
-    std::sort(ForEachMacros.begin(), ForEachMacros.end());
-  }
-
-  ArrayRef<FormatToken *> lex() {
-    assert(Tokens.empty());
-    assert(FirstInLineIndex == 0);
-    do {
-      Tokens.push_back(getNextToken());
-      if (Style.Language == FormatStyle::LK_JavaScript)
-        tryParseJSRegexLiteral();
-      tryMergePreviousTokens();
-      if (Tokens.back()->NewlinesBefore > 0 || Tokens.back()->IsMultiline)
-        FirstInLineIndex = Tokens.size() - 1;
-    } while (Tokens.back()->Tok.isNot(tok::eof));
-    return Tokens;
-  }
-
-  const AdditionalKeywords &getKeywords() { return Keywords; }
-
-private:
-  void tryMergePreviousTokens() {
-    if (tryMerge_TMacro())
-      return;
-    if (tryMergeConflictMarkers())
-      return;
-    if (tryMergeLessLess())
-      return;
-
-    if (Style.Language == FormatStyle::LK_JavaScript) {
-      if (tryMergeTemplateString())
-        return;
-
-      static const tok::TokenKind JSIdentity[] = {tok::equalequal, tok::equal};
-      static const tok::TokenKind JSNotIdentity[] = {tok::exclaimequal,
-                                                     tok::equal};
-      static const tok::TokenKind JSShiftEqual[] = {tok::greater, tok::greater,
-                                                    tok::greaterequal};
-      static const tok::TokenKind JSRightArrow[] = {tok::equal, tok::greater};
-      // FIXME: Investigate what token type gives the correct operator priority.
-      if (tryMergeTokens(JSIdentity, TT_BinaryOperator))
-        return;
-      if (tryMergeTokens(JSNotIdentity, TT_BinaryOperator))
-        return;
-      if (tryMergeTokens(JSShiftEqual, TT_BinaryOperator))
-        return;
-      if (tryMergeTokens(JSRightArrow, TT_JsFatArrow))
-        return;
-    }
-  }
-
-  bool tryMergeLessLess() {
-    // Merge X,less,less,Y into X,lessless,Y unless X or Y is less.
-    if (Tokens.size() < 3)
-      return false;
-
-    bool FourthTokenIsLess = false;
-    if (Tokens.size() > 3)
-      FourthTokenIsLess = (Tokens.end() - 4)[0]->is(tok::less);
-
-    auto First = Tokens.end() - 3;
-    if (First[2]->is(tok::less) || First[1]->isNot(tok::less) ||
-        First[0]->isNot(tok::less) || FourthTokenIsLess)
-      return false;
-
-    // Only merge if there currently is no whitespace between the two "<".
-    if (First[1]->WhitespaceRange.getBegin() !=
-        First[1]->WhitespaceRange.getEnd())
-      return false;
-
-    First[0]->Tok.setKind(tok::lessless);
-    First[0]->TokenText = "<<";
-    First[0]->ColumnWidth += 1;
-    Tokens.erase(Tokens.end() - 2);
-    return true;
-  }
-
-  bool tryMergeTokens(ArrayRef<tok::TokenKind> Kinds, TokenType NewType) {
-    if (Tokens.size() < Kinds.size())
-      return false;
-
-    SmallVectorImpl<FormatToken *>::const_iterator First =
-        Tokens.end() - Kinds.size();
-    if (!First[0]->is(Kinds[0]))
-      return false;
-    unsigned AddLength = 0;
-    for (unsigned i = 1; i < Kinds.size(); ++i) {
-      if (!First[i]->is(Kinds[i]) ||
-          First[i]->WhitespaceRange.getBegin() !=
-              First[i]->WhitespaceRange.getEnd())
-        return false;
-      AddLength += First[i]->TokenText.size();
-    }
-    Tokens.resize(Tokens.size() - Kinds.size() + 1);
-    First[0]->TokenText = StringRef(First[0]->TokenText.data(),
-                                    First[0]->TokenText.size() + AddLength);
-    First[0]->ColumnWidth += AddLength;
-    First[0]->Type = NewType;
-    return true;
-  }
-
-  // Returns \c true if \p Tok can only be followed by an operand in JavaScript.
-  bool precedesOperand(FormatToken *Tok) {
-    // NB: This is not entirely correct, as an r_paren can introduce an operand
-    // location in e.g. `if (foo) /bar/.exec(...);`. That is a rare enough
-    // corner case to not matter in practice, though.
-    return Tok->isOneOf(tok::period, tok::l_paren, tok::comma, tok::l_brace,
-                        tok::r_brace, tok::l_square, tok::semi, tok::exclaim,
-                        tok::colon, tok::question, tok::tilde) ||
-           Tok->isOneOf(tok::kw_return, tok::kw_do, tok::kw_case, tok::kw_throw,
-                        tok::kw_else, tok::kw_new, tok::kw_delete, tok::kw_void,
-                        tok::kw_typeof, Keywords.kw_instanceof,
-                        Keywords.kw_in) ||
-           Tok->isBinaryOperator();
-  }
-
-  bool canPrecedeRegexLiteral(FormatToken *Prev) {
-    if (!Prev)
-      return true;
-
-    // Regex literals can only follow after prefix unary operators, not after
-    // postfix unary operators. If the '++' is followed by a non-operand
-    // introducing token, the slash here is the operand and not the start of a
-    // regex.
-    if (Prev->isOneOf(tok::plusplus, tok::minusminus))
-      return (Tokens.size() < 3 || precedesOperand(Tokens[Tokens.size() - 3]));
-
-    // The previous token must introduce an operand location where regex
-    // literals can occur.
-    if (!precedesOperand(Prev))
-      return false;
-
-    return true;
-  }
-
-  // Tries to parse a JavaScript Regex literal starting at the current token,
-  // if that begins with a slash and is in a location where JavaScript allows
-  // regex literals. Changes the current token to a regex literal and updates
-  // its text if successful.
-  void tryParseJSRegexLiteral() {
-    FormatToken *RegexToken = Tokens.back();
-    if (!RegexToken->isOneOf(tok::slash, tok::slashequal))
-      return;
-
-    FormatToken *Prev = nullptr;
-    for (auto I = Tokens.rbegin() + 1, E = Tokens.rend(); I != E; ++I) {
-      // NB: Because previous pointers are not initialized yet, this cannot use
-      // Token.getPreviousNonComment.
-      if ((*I)->isNot(tok::comment)) {
-        Prev = *I;
-        break;
-      }
-    }
-
-    if (!canPrecedeRegexLiteral(Prev))
-      return;
-
-    // 'Manually' lex ahead in the current file buffer.
-    const char *Offset = Lex->getBufferLocation();
-    const char *RegexBegin = Offset - RegexToken->TokenText.size();
-    StringRef Buffer = Lex->getBuffer();
-    bool InCharacterClass = false;
-    bool HaveClosingSlash = false;
-    for (; !HaveClosingSlash && Offset != Buffer.end(); ++Offset) {
-      // Regular expressions are terminated with a '/', which can only be
-      // escaped using '\' or a character class between '[' and ']'.
-      // See http://www.ecma-international.org/ecma-262/5.1/#sec-7.8.5.
-      switch (*Offset) {
-      case '\\':
-        // Skip the escaped character.
-        ++Offset;
-        break;
-      case '[':
-        InCharacterClass = true;
-        break;
-      case ']':
-        InCharacterClass = false;
-        break;
-      case '/':
-        if (!InCharacterClass)
-          HaveClosingSlash = true;
-        break;
-      }
-    }
-
-    RegexToken->Type = TT_RegexLiteral;
-    // Treat regex literals like other string_literals.
-    RegexToken->Tok.setKind(tok::string_literal);
-    RegexToken->TokenText = StringRef(RegexBegin, Offset - RegexBegin);
-    RegexToken->ColumnWidth = RegexToken->TokenText.size();
-
-    resetLexer(SourceMgr.getFileOffset(Lex->getSourceLocation(Offset)));
-  }
-
-  bool tryMergeTemplateString() {
-    if (Tokens.size() < 2)
-      return false;
-
-    FormatToken *EndBacktick = Tokens.back();
-    // Backticks get lexed as tok::unknown tokens. If a template string contains
-    // a comment start, it gets lexed as a tok::comment, or tok::unknown if
-    // unterminated.
-    if (!EndBacktick->isOneOf(tok::comment, tok::string_literal,
-                              tok::char_constant, tok::unknown))
-      return false;
-    size_t CommentBacktickPos = EndBacktick->TokenText.find('`');
-    // Unknown token that's not actually a backtick, or a comment that doesn't
-    // contain a backtick.
-    if (CommentBacktickPos == StringRef::npos)
-      return false;
-
-    unsigned TokenCount = 0;
-    bool IsMultiline = false;
-    unsigned EndColumnInFirstLine =
-        EndBacktick->OriginalColumn + EndBacktick->ColumnWidth;
-    for (auto I = Tokens.rbegin() + 1, E = Tokens.rend(); I != E; I++) {
-      ++TokenCount;
-      if (I[0]->IsMultiline)
-        IsMultiline = true;
-
-      // If there was a preceding template string, this must be the start of a
-      // template string, not the end.
-      if (I[0]->is(TT_TemplateString))
-        return false;
-
-      if (I[0]->isNot(tok::unknown) || I[0]->TokenText != "`") {
-        // Keep track of the rhs offset of the last token to wrap across lines -
-        // its the rhs offset of the first line of the template string, used to
-        // determine its width.
-        if (I[0]->IsMultiline)
-          EndColumnInFirstLine = I[0]->OriginalColumn + I[0]->ColumnWidth;
-        // If the token has newlines, the token before it (if it exists) is the
-        // rhs end of the previous line.
-        if (I[0]->NewlinesBefore > 0 && (I + 1 != E)) {
-          EndColumnInFirstLine = I[1]->OriginalColumn + I[1]->ColumnWidth;
-          IsMultiline = true;
-        }
-        continue;
-      }
-
-      Tokens.resize(Tokens.size() - TokenCount);
-      Tokens.back()->Type = TT_TemplateString;
-      const char *EndOffset =
-          EndBacktick->TokenText.data() + 1 + CommentBacktickPos;
-      if (CommentBacktickPos != 0) {
-        // If the backtick was not the first character (e.g. in a comment),
-        // re-lex after the backtick position.
-        SourceLocation Loc = EndBacktick->Tok.getLocation();
-        resetLexer(SourceMgr.getFileOffset(Loc) + CommentBacktickPos + 1);
-      }
-      Tokens.back()->TokenText =
-          StringRef(Tokens.back()->TokenText.data(),
-                    EndOffset - Tokens.back()->TokenText.data());
-
-      unsigned EndOriginalColumn = EndBacktick->OriginalColumn;
-      if (EndOriginalColumn == 0) {
-        SourceLocation Loc = EndBacktick->Tok.getLocation();
-        EndOriginalColumn = SourceMgr.getSpellingColumnNumber(Loc);
-      }
-      // If the ` is further down within the token (e.g. in a comment).
-      EndOriginalColumn += CommentBacktickPos;
-
-      if (IsMultiline) {
-        // ColumnWidth is from backtick to last token in line.
-        // LastLineColumnWidth is 0 to backtick.
-        // x = `some content
-        //     until here`;
-        Tokens.back()->ColumnWidth =
-            EndColumnInFirstLine - Tokens.back()->OriginalColumn;
-        // +1 for the ` itself.
-        Tokens.back()->LastLineColumnWidth = EndOriginalColumn + 1;
-        Tokens.back()->IsMultiline = true;
-      } else {
-        // Token simply spans from start to end, +1 for the ` itself.
-        Tokens.back()->ColumnWidth =
-            EndOriginalColumn - Tokens.back()->OriginalColumn + 1;
-      }
-      return true;
-    }
-    return false;
-  }
-
-  bool tryMerge_TMacro() {
-    if (Tokens.size() < 4)
-      return false;
-    FormatToken *Last = Tokens.back();
-    if (!Last->is(tok::r_paren))
-      return false;
-
-    FormatToken *String = Tokens[Tokens.size() - 2];
-    if (!String->is(tok::string_literal) || String->IsMultiline)
-      return false;
-
-    if (!Tokens[Tokens.size() - 3]->is(tok::l_paren))
-      return false;
-
-    FormatToken *Macro = Tokens[Tokens.size() - 4];
-    if (Macro->TokenText != "_T")
-      return false;
-
-    const char *Start = Macro->TokenText.data();
-    const char *End = Last->TokenText.data() + Last->TokenText.size();
-    String->TokenText = StringRef(Start, End - Start);
-    String->IsFirst = Macro->IsFirst;
-    String->LastNewlineOffset = Macro->LastNewlineOffset;
-    String->WhitespaceRange = Macro->WhitespaceRange;
-    String->OriginalColumn = Macro->OriginalColumn;
-    String->ColumnWidth = encoding::columnWidthWithTabs(
-        String->TokenText, String->OriginalColumn, Style.TabWidth, Encoding);
-    String->NewlinesBefore = Macro->NewlinesBefore;
-    String->HasUnescapedNewline = Macro->HasUnescapedNewline;
-
-    Tokens.pop_back();
-    Tokens.pop_back();
-    Tokens.pop_back();
-    Tokens.back() = String;
-    return true;
-  }
-
-  bool tryMergeConflictMarkers() {
-    if (Tokens.back()->NewlinesBefore == 0 && Tokens.back()->isNot(tok::eof))
-      return false;
-
-    // Conflict lines look like:
-    // <marker> <text from the vcs>
-    // For example:
-    // >>>>>>> /file/in/file/system at revision 1234
-    //
-    // We merge all tokens in a line that starts with a conflict marker
-    // into a single token with a special token type that the unwrapped line
-    // parser will use to correctly rebuild the underlying code.
-
-    FileID ID;
-    // Get the position of the first token in the line.
-    unsigned FirstInLineOffset;
-    std::tie(ID, FirstInLineOffset) = SourceMgr.getDecomposedLoc(
-        Tokens[FirstInLineIndex]->getStartOfNonWhitespace());
-    StringRef Buffer = SourceMgr.getBuffer(ID)->getBuffer();
-    // Calculate the offset of the start of the current line.
-    auto LineOffset = Buffer.rfind('\n', FirstInLineOffset);
-    if (LineOffset == StringRef::npos) {
-      LineOffset = 0;
-    } else {
-      ++LineOffset;
-    }
-
-    auto FirstSpace = Buffer.find_first_of(" \n", LineOffset);
-    StringRef LineStart;
-    if (FirstSpace == StringRef::npos) {
-      LineStart = Buffer.substr(LineOffset);
-    } else {
-      LineStart = Buffer.substr(LineOffset, FirstSpace - LineOffset);
-    }
-
-    TokenType Type = TT_Unknown;
-    if (LineStart == "<<<<<<<" || LineStart == ">>>>") {
-      Type = TT_ConflictStart;
-    } else if (LineStart == "|||||||" || LineStart == "=======" ||
-               LineStart == "====") {
-      Type = TT_ConflictAlternative;
-    } else if (LineStart == ">>>>>>>" || LineStart == "<<<<") {
-      Type = TT_ConflictEnd;
-    }
-
-    if (Type != TT_Unknown) {
-      FormatToken *Next = Tokens.back();
-
-      Tokens.resize(FirstInLineIndex + 1);
-      // We do not need to build a complete token here, as we will skip it
-      // during parsing anyway (as we must not touch whitespace around conflict
-      // markers).
-      Tokens.back()->Type = Type;
-      Tokens.back()->Tok.setKind(tok::kw___unknown_anytype);
-
-      Tokens.push_back(Next);
-      return true;
-    }
-
-    return false;
-  }
-
-  FormatToken *getStashedToken() {
-    // Create a synthesized second '>' or '<' token.
-    Token Tok = FormatTok->Tok;
-    StringRef TokenText = FormatTok->TokenText;
-
-    unsigned OriginalColumn = FormatTok->OriginalColumn;
-    FormatTok = new (Allocator.Allocate()) FormatToken;
-    FormatTok->Tok = Tok;
-    SourceLocation TokLocation =
-        FormatTok->Tok.getLocation().getLocWithOffset(Tok.getLength() - 1);
-    FormatTok->Tok.setLocation(TokLocation);
-    FormatTok->WhitespaceRange = SourceRange(TokLocation, TokLocation);
-    FormatTok->TokenText = TokenText;
-    FormatTok->ColumnWidth = 1;
-    FormatTok->OriginalColumn = OriginalColumn + 1;
-
-    return FormatTok;
-  }
-
-  FormatToken *getNextToken() {
-    if (GreaterStashed) {
-      GreaterStashed = false;
-      return getStashedToken();
-    }
-    if (LessStashed) {
-      LessStashed = false;
-      return getStashedToken();
-    }
-
-    FormatTok = new (Allocator.Allocate()) FormatToken;
-    readRawToken(*FormatTok);
-    SourceLocation WhitespaceStart =
-        FormatTok->Tok.getLocation().getLocWithOffset(-TrailingWhitespace);
-    FormatTok->IsFirst = IsFirstToken;
-    IsFirstToken = false;
-
-    // Consume and record whitespace until we find a significant token.
-    unsigned WhitespaceLength = TrailingWhitespace;
-    while (FormatTok->Tok.is(tok::unknown)) {
-      StringRef Text = FormatTok->TokenText;
-      auto EscapesNewline = [&](int pos) {
-        // A '\r' here is just part of '\r\n'. Skip it.
-        if (pos >= 0 && Text[pos] == '\r')
-          --pos;
-        // See whether there is an odd number of '\' before this.
-        unsigned count = 0;
-        for (; pos >= 0; --pos, ++count)
-          if (Text[pos] != '\\')
-            break;
-        return count & 1;
-      };
-      // FIXME: This miscounts tok:unknown tokens that are not just
-      // whitespace, e.g. a '`' character.
-      for (int i = 0, e = Text.size(); i != e; ++i) {
-        switch (Text[i]) {
-        case '\n':
-          ++FormatTok->NewlinesBefore;
-          FormatTok->HasUnescapedNewline = !EscapesNewline(i - 1);
-          FormatTok->LastNewlineOffset = WhitespaceLength + i + 1;
-          Column = 0;
-          break;
-        case '\r':
-          FormatTok->LastNewlineOffset = WhitespaceLength + i + 1;
-          Column = 0;
-          break;
-        case '\f':
-        case '\v':
-          Column = 0;
-          break;
-        case ' ':
-          ++Column;
-          break;
-        case '\t':
-          Column += Style.TabWidth - Column % Style.TabWidth;
-          break;
-        case '\\':
-          if (i + 1 == e || (Text[i + 1] != '\r' && Text[i + 1] != '\n'))
-            FormatTok->Type = TT_ImplicitStringLiteral;
-          break;
-        default:
-          FormatTok->Type = TT_ImplicitStringLiteral;
-          break;
-        }
-        if (FormatTok->Type == TT_ImplicitStringLiteral)
-          break;
-      }
-
-      if (FormatTok->is(TT_ImplicitStringLiteral))
-        break;
-      WhitespaceLength += FormatTok->Tok.getLength();
-
-      readRawToken(*FormatTok);
-    }
-
-    // In case the token starts with escaped newlines, we want to
-    // take them into account as whitespace - this pattern is quite frequent
-    // in macro definitions.
-    // FIXME: Add a more explicit test.
-    while (FormatTok->TokenText.size() > 1 && FormatTok->TokenText[0] == '\\' &&
-           FormatTok->TokenText[1] == '\n') {
-      ++FormatTok->NewlinesBefore;
-      WhitespaceLength += 2;
-      FormatTok->LastNewlineOffset = 2;
-      Column = 0;
-      FormatTok->TokenText = FormatTok->TokenText.substr(2);
-    }
-
-    FormatTok->WhitespaceRange = SourceRange(
-        WhitespaceStart, WhitespaceStart.getLocWithOffset(WhitespaceLength));
-
-    FormatTok->OriginalColumn = Column;
-
-    TrailingWhitespace = 0;
-    if (FormatTok->Tok.is(tok::comment)) {
-      // FIXME: Add the trimmed whitespace to Column.
-      StringRef UntrimmedText = FormatTok->TokenText;
-      FormatTok->TokenText = FormatTok->TokenText.rtrim(" \t\v\f");
-      TrailingWhitespace = UntrimmedText.size() - FormatTok->TokenText.size();
-    } else if (FormatTok->Tok.is(tok::raw_identifier)) {
-      IdentifierInfo &Info = IdentTable.get(FormatTok->TokenText);
-      FormatTok->Tok.setIdentifierInfo(&Info);
-      FormatTok->Tok.setKind(Info.getTokenID());
-      if (Style.Language == FormatStyle::LK_Java &&
-          FormatTok->isOneOf(tok::kw_struct, tok::kw_union, tok::kw_delete,
-                             tok::kw_operator)) {
-        FormatTok->Tok.setKind(tok::identifier);
-        FormatTok->Tok.setIdentifierInfo(nullptr);
-      } else if (Style.Language == FormatStyle::LK_JavaScript &&
-                 FormatTok->isOneOf(tok::kw_struct, tok::kw_union,
-                                    tok::kw_operator)) {
-        FormatTok->Tok.setKind(tok::identifier);
-        FormatTok->Tok.setIdentifierInfo(nullptr);
-      }
-    } else if (FormatTok->Tok.is(tok::greatergreater)) {
-      FormatTok->Tok.setKind(tok::greater);
-      FormatTok->TokenText = FormatTok->TokenText.substr(0, 1);
-      GreaterStashed = true;
-    } else if (FormatTok->Tok.is(tok::lessless)) {
-      FormatTok->Tok.setKind(tok::less);
-      FormatTok->TokenText = FormatTok->TokenText.substr(0, 1);
-      LessStashed = true;
-    }
-
-    // Now FormatTok is the next non-whitespace token.
-
-    StringRef Text = FormatTok->TokenText;
-    size_t FirstNewlinePos = Text.find('\n');
-    if (FirstNewlinePos == StringRef::npos) {
-      // FIXME: ColumnWidth actually depends on the start column, we need to
-      // take this into account when the token is moved.
-      FormatTok->ColumnWidth =
-          encoding::columnWidthWithTabs(Text, Column, Style.TabWidth, Encoding);
-      Column += FormatTok->ColumnWidth;
-    } else {
-      FormatTok->IsMultiline = true;
-      // FIXME: ColumnWidth actually depends on the start column, we need to
-      // take this into account when the token is moved.
-      FormatTok->ColumnWidth = encoding::columnWidthWithTabs(
-          Text.substr(0, FirstNewlinePos), Column, Style.TabWidth, Encoding);
-
-      // The last line of the token always starts in column 0.
-      // Thus, the length can be precomputed even in the presence of tabs.
-      FormatTok->LastLineColumnWidth = encoding::columnWidthWithTabs(
-          Text.substr(Text.find_last_of('\n') + 1), 0, Style.TabWidth,
-          Encoding);
-      Column = FormatTok->LastLineColumnWidth;
-    }
-
-    if (Style.Language == FormatStyle::LK_Cpp) {
-      if (!(Tokens.size() > 0 && Tokens.back()->Tok.getIdentifierInfo() &&
-            Tokens.back()->Tok.getIdentifierInfo()->getPPKeywordID() ==
-                tok::pp_define) &&
-          std::find(ForEachMacros.begin(), ForEachMacros.end(),
-                    FormatTok->Tok.getIdentifierInfo()) !=
-              ForEachMacros.end()) {
-        FormatTok->Type = TT_ForEachMacro;
-      } else if (FormatTok->is(tok::identifier)) {
-        if (MacroBlockBeginRegex.match(Text)) {
-          FormatTok->Type = TT_MacroBlockBegin;
-        } else if (MacroBlockEndRegex.match(Text)) {
-          FormatTok->Type = TT_MacroBlockEnd;
-        }
-      }
-    }
-
-    return FormatTok;
-  }
-
-  FormatToken *FormatTok;
-  bool IsFirstToken;
-  bool GreaterStashed, LessStashed;
-  unsigned Column;
-  unsigned TrailingWhitespace;
-  std::unique_ptr<Lexer> Lex;
-  const SourceManager &SourceMgr;
-  FileID ID;
-  const FormatStyle &Style;
-  IdentifierTable IdentTable;
-  AdditionalKeywords Keywords;
-  encoding::Encoding Encoding;
-  llvm::SpecificBumpPtrAllocator<FormatToken> Allocator;
-  // Index (in 'Tokens') of the last token that starts a new line.
-  unsigned FirstInLineIndex;
-  SmallVector<FormatToken *, 16> Tokens;
-  SmallVector<IdentifierInfo *, 8> ForEachMacros;
-
-  bool FormattingDisabled;
-
-  llvm::Regex MacroBlockBeginRegex;
-  llvm::Regex MacroBlockEndRegex;
-
-  void readRawToken(FormatToken &Tok) {
-    Lex->LexFromRawLexer(Tok.Tok);
-    Tok.TokenText = StringRef(SourceMgr.getCharacterData(Tok.Tok.getLocation()),
-                              Tok.Tok.getLength());
-    // For formatting, treat unterminated string literals like normal string
-    // literals.
-    if (Tok.is(tok::unknown)) {
-      if (!Tok.TokenText.empty() && Tok.TokenText[0] == '"') {
-        Tok.Tok.setKind(tok::string_literal);
-        Tok.IsUnterminatedLiteral = true;
-      } else if (Style.Language == FormatStyle::LK_JavaScript &&
-                 Tok.TokenText == "''") {
-        Tok.Tok.setKind(tok::string_literal);
-      }
-    }
-
-    if (Style.Language == FormatStyle::LK_JavaScript &&
-        Tok.is(tok::char_constant)) {
-      Tok.Tok.setKind(tok::string_literal);
-    }
-
-    if (Tok.is(tok::comment) && (Tok.TokenText == "// clang-format on" ||
-                                 Tok.TokenText == "/* clang-format on */")) {
-      FormattingDisabled = false;
-    }
-
-    Tok.Finalized = FormattingDisabled;
-
-    if (Tok.is(tok::comment) && (Tok.TokenText == "// clang-format off" ||
-                                 Tok.TokenText == "/* clang-format off */")) {
-      FormattingDisabled = true;
-    }
-  }
-
-  void resetLexer(unsigned Offset) {
-    StringRef Buffer = SourceMgr.getBufferData(ID);
-    Lex.reset(new Lexer(SourceMgr.getLocForStartOfFile(ID),
-                        getFormattingLangOpts(Style), Buffer.begin(),
-                        Buffer.begin() + Offset, Buffer.end()));
-    Lex->SetKeepWhitespaceMode(true);
-    TrailingWhitespace = 0;
-  }
-};
-
-static StringRef getLanguageName(FormatStyle::LanguageKind Language) {
-  switch (Language) {
-  case FormatStyle::LK_Cpp:
-    return "C++";
-  case FormatStyle::LK_Java:
-    return "Java";
-  case FormatStyle::LK_JavaScript:
-    return "JavaScript";
-  case FormatStyle::LK_Proto:
-    return "Proto";
-  default:
-    return "Unknown";
-  }
-}
-
-class Environment {
-public:
-  Environment(SourceManager &SM, FileID ID, ArrayRef<CharSourceRange> Ranges)
-      : ID(ID), CharRanges(Ranges.begin(), Ranges.end()), SM(SM) {}
-
-  Environment(FileID ID, std::unique_ptr<FileManager> FileMgr,
-              std::unique_ptr<SourceManager> VirtualSM,
-              std::unique_ptr<DiagnosticsEngine> Diagnostics,
-              const std::vector<CharSourceRange> &CharRanges)
-      : ID(ID), CharRanges(CharRanges.begin(), CharRanges.end()),
-        SM(*VirtualSM), FileMgr(std::move(FileMgr)),
-        VirtualSM(std::move(VirtualSM)), Diagnostics(std::move(Diagnostics)) {}
-
-  // This sets up an virtual file system with file \p FileName containing \p
-  // Code.
-  static std::unique_ptr<Environment>
-  CreateVirtualEnvironment(StringRef Code, StringRef FileName,
-                           ArrayRef<tooling::Range> Ranges) {
-    // This is referenced by `FileMgr` and will be released by `FileMgr` when it
-    // is deleted.
-    IntrusiveRefCntPtr<vfs::InMemoryFileSystem> InMemoryFileSystem(
-        new vfs::InMemoryFileSystem);
-    // This is passed to `SM` as reference, so the pointer has to be referenced
-    // in `Environment` so that `FileMgr` can out-live this function scope.
-    std::unique_ptr<FileManager> FileMgr(
-        new FileManager(FileSystemOptions(), InMemoryFileSystem));
-    // This is passed to `SM` as reference, so the pointer has to be referenced
-    // by `Environment` due to the same reason above.
-    std::unique_ptr<DiagnosticsEngine> Diagnostics(new DiagnosticsEngine(
-        IntrusiveRefCntPtr<DiagnosticIDs>(new DiagnosticIDs),
-        new DiagnosticOptions));
-    // This will be stored as reference, so the pointer has to be stored in
-    // due to the same reason above.
-    std::unique_ptr<SourceManager> VirtualSM(
-        new SourceManager(*Diagnostics, *FileMgr));
-    InMemoryFileSystem->addFile(
-        FileName, 0, llvm::MemoryBuffer::getMemBuffer(
-                         Code, FileName, /*RequiresNullTerminator=*/false));
-    FileID ID = VirtualSM->createFileID(
-        FileMgr->getFile(FileName), SourceLocation(), clang::SrcMgr::C_User);
-    assert(ID.isValid());
-    SourceLocation StartOfFile = VirtualSM->getLocForStartOfFile(ID);
-    std::vector<CharSourceRange> CharRanges;
-    for (const tooling::Range &Range : Ranges) {
-      SourceLocation Start = StartOfFile.getLocWithOffset(Range.getOffset());
-      SourceLocation End = Start.getLocWithOffset(Range.getLength());
-      CharRanges.push_back(CharSourceRange::getCharRange(Start, End));
-    }
-    return llvm::make_unique<Environment>(ID, std::move(FileMgr),
-                                          std::move(VirtualSM),
-                                          std::move(Diagnostics), CharRanges);
-  }
-
-  FileID getFileID() const { return ID; }
-
-  StringRef getFileName() const { return FileName; }
-
-  ArrayRef<CharSourceRange> getCharRanges() const { return CharRanges; }
-
-  const SourceManager &getSourceManager() const { return SM; }
-
-private:
-  FileID ID;
-  StringRef FileName;
-  SmallVector<CharSourceRange, 8> CharRanges;
-  SourceManager &SM;
-
-  // The order of these fields are important - they should be in the same order
-  // as they are created in `CreateVirtualEnvironment` so that they can be
-  // deleted in the reverse order as they are created.
-  std::unique_ptr<FileManager> FileMgr;
-  std::unique_ptr<SourceManager> VirtualSM;
-  std::unique_ptr<DiagnosticsEngine> Diagnostics;
-};
-
-class TokenAnalyzer : public UnwrappedLineConsumer {
-public:
-  TokenAnalyzer(const Environment &Env, const FormatStyle &Style)
-      : Style(Style), Env(Env),
-        AffectedRangeMgr(Env.getSourceManager(), Env.getCharRanges()),
-        UnwrappedLines(1),
-        Encoding(encoding::detectEncoding(
-            Env.getSourceManager().getBufferData(Env.getFileID()))) {
-    DEBUG(llvm::dbgs() << "File encoding: "
-                       << (Encoding == encoding::Encoding_UTF8 ? "UTF8"
-                                                               : "unknown")
-                       << "\n");
-    DEBUG(llvm::dbgs() << "Language: " << getLanguageName(Style.Language)
-                       << "\n");
-  }
-
-  tooling::Replacements process() {
-    tooling::Replacements Result;
-    FormatTokenLexer Tokens(Env.getSourceManager(), Env.getFileID(), Style,
-                            Encoding);
-
-    UnwrappedLineParser Parser(Style, Tokens.getKeywords(), Tokens.lex(),
-                               *this);
-    Parser.parse();
-    assert(UnwrappedLines.rbegin()->empty());
-    for (unsigned Run = 0, RunE = UnwrappedLines.size(); Run + 1 != RunE;
-         ++Run) {
-      DEBUG(llvm::dbgs() << "Run " << Run << "...\n");
-      SmallVector<AnnotatedLine *, 16> AnnotatedLines;
-
-      TokenAnnotator Annotator(Style, Tokens.getKeywords());
-      for (unsigned i = 0, e = UnwrappedLines[Run].size(); i != e; ++i) {
-        AnnotatedLines.push_back(new AnnotatedLine(UnwrappedLines[Run][i]));
-        Annotator.annotate(*AnnotatedLines.back());
-      }
-
-      tooling::Replacements RunResult =
-          analyze(Annotator, AnnotatedLines, Tokens, Result);
-
-      DEBUG({
-        llvm::dbgs() << "Replacements for run " << Run << ":\n";
-        for (tooling::Replacements::iterator I = RunResult.begin(),
-                                             E = RunResult.end();
-             I != E; ++I) {
-          llvm::dbgs() << I->toString() << "\n";
-        }
-      });
-      for (unsigned i = 0, e = AnnotatedLines.size(); i != e; ++i) {
-        delete AnnotatedLines[i];
-      }
-      Result.insert(RunResult.begin(), RunResult.end());
-    }
-    return Result;
-  }
-
-protected:
-  virtual tooling::Replacements
-  analyze(TokenAnnotator &Annotator,
-          SmallVectorImpl<AnnotatedLine *> &AnnotatedLines,
-          FormatTokenLexer &Tokens, tooling::Replacements &Result) = 0;
-
-  void consumeUnwrappedLine(const UnwrappedLine &TheLine) override {
-    assert(!UnwrappedLines.empty());
-    UnwrappedLines.back().push_back(TheLine);
-  }
-
-  void finishRun() override {
-    UnwrappedLines.push_back(SmallVector<UnwrappedLine, 16>());
-  }
-
-  FormatStyle Style;
-  // Stores Style, FileID and SourceManager etc.
-  const Environment &Env;
-  // AffectedRangeMgr stores ranges to be fixed.
-  AffectedRangeManager AffectedRangeMgr;
-  SmallVector<SmallVector<UnwrappedLine, 16>, 2> UnwrappedLines;
-  encoding::Encoding Encoding;
-};
-
 class Formatter : public TokenAnalyzer {
 public:
   Formatter(const Environment &Env, const FormatStyle &Style,
             bool *IncompleteFormat)
       : TokenAnalyzer(Env, Style), IncompleteFormat(IncompleteFormat) {}
 
   tooling::Replacements
   analyze(TokenAnnotator &Annotator,
private:
 
   // Tokens to be deleted.
   std::set<FormatToken *, FormatTokenLess> DeletedTokens;
   // The line numbers of lines to be deleted.
   std::set<unsigned> DeletedLines;
 };
 
 struct IncludeDirective {
   StringRef Filename;
   StringRef Text;
   unsigned Offset;
   int Category;
 };
 
 } // end anonymous namespace
 
 // Determines whether 'Ranges' intersects with ('Start', 'End').
static void sortIncludes(const FormatStyle &Style,
   assert(result.size() ==
          Includes.back().Offset + Includes.back().Text.size() -
              Includes.front().Offset);
 
   Replaces.insert(tooling::Replacement(FileName, Includes.front().Offset,
                                        result.size(), result));
 }
 
 tooling::Replacements sortIncludes(const FormatStyle &Style, StringRef Code,
                                    ArrayRef<tooling::Range> Ranges,
                                    StringRef FileName, unsigned *Cursor) {
   tooling::Replacements Replaces;
   if (!Style.SortIncludes)
     return Replaces;
+  if (Style.Language == FormatStyle::LanguageKind::LK_JavaScript)
+    return sortJavaScriptImports(Style, Code, Ranges, FileName);
 
   unsigned Prev = 0;
   unsigned SearchFrom = 0;
   llvm::Regex IncludeRegex(
       R"(^[\t\ ]*#[\t\ ]*(import|include)[^"<]*(["<][^">]*[">]))");
   SmallVector<StringRef, 4> Matches;
   SmallVector<IncludeDirective, 16> IncludesInBlock;
 
   // In compiled files, consider the first #include to be the main #include of

lib/Format/FormatToken.h

AdditionalKeywords(IdentifierTable &IdentTable) {
     kw_override = &IdentTable.get("override");
     kw_in = &IdentTable.get("in");
     kw_of = &IdentTable.get("of");
     kw_CF_ENUM = &IdentTable.get("CF_ENUM");
     kw_CF_OPTIONS = &IdentTable.get("CF_OPTIONS");
     kw_NS_ENUM = &IdentTable.get("NS_ENUM");
     kw_NS_OPTIONS = &IdentTable.get("NS_OPTIONS");
 
+    kw_as = &IdentTable.get("as");
     kw_async = &IdentTable.get("async");
     kw_await = &IdentTable.get("await");
     kw_finally = &IdentTable.get("finally");
     kw_from = &IdentTable.get("from");
     kw_function = &IdentTable.get("function");
     kw_import = &IdentTable.get("import");
     kw_is = &IdentTable.get("is");
     kw_let = &IdentTable.get("let");
struct AdditionalKeywords {
   IdentifierInfo *kw_of;
   IdentifierInfo *kw_CF_ENUM;
   IdentifierInfo *kw_CF_OPTIONS;
   IdentifierInfo *kw_NS_ENUM;
   IdentifierInfo *kw_NS_OPTIONS;
   IdentifierInfo *kw___except;
 
   // JavaScript keywords.
+  IdentifierInfo *kw_as;
   IdentifierInfo *kw_async;
   IdentifierInfo *kw_await;
   IdentifierInfo *kw_finally;
   IdentifierInfo *kw_from;
   IdentifierInfo *kw_function;
   IdentifierInfo *kw_import;
   IdentifierInfo *kw_is;
   IdentifierInfo *kw_let;

lib/Format/FormatTokenLexer.h

+//===--- FormatTokenLexer.h - Format C++ code ----------------*- C++ ----*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file contains FormatTokenLexer, which tokenizes a source file
+/// into a token stream suitable for ClangFormat.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_LIB_FORMAT_FORMATTOKENLEXER_H
+#define LLVM_CLANG_LIB_FORMAT_FORMATTOKENLEXER_H
+
+#include "Encoding.h"
+#include "FormatToken.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Format/Format.h"
+#include "llvm/Support/Regex.h"
+
+namespace clang {
+namespace format {
+
+class FormatTokenLexer {
+public:
+  FormatTokenLexer(const SourceManager &SourceMgr, FileID ID,
+                   const FormatStyle &Style, encoding::Encoding Encoding);
+
+  ArrayRef<FormatToken *> lex();
+
+  const AdditionalKeywords &getKeywords() { return Keywords; }
+
+private:
+  void tryMergePreviousTokens();
+
+  bool tryMergeLessLess();
+
+  bool tryMergeTokens(ArrayRef<tok::TokenKind> Kinds, TokenType NewType);
+
+  // Returns \c true if \p Tok can only be followed by an operand in JavaScript.
+  bool precedesOperand(FormatToken *Tok);
+
+  bool canPrecedeRegexLiteral(FormatToken *Prev);
+
+  // Tries to parse a JavaScript Regex literal starting at the current token,
+  // if that begins with a slash and is in a location where JavaScript allows
+  // regex literals. Changes the current token to a regex literal and updates
+  // its text if successful.
+  void tryParseJSRegexLiteral();
+
+  bool tryMergeTemplateString();
+
+  bool tryMerge_TMacro();
+
+  bool tryMergeConflictMarkers();
+
+  FormatToken *getStashedToken();
+
+  FormatToken *getNextToken();
+
+  FormatToken *FormatTok;
+  bool IsFirstToken;
+  bool GreaterStashed, LessStashed;
+  unsigned Column;
+  unsigned TrailingWhitespace;
+  std::unique_ptr<Lexer> Lex;
+  const SourceManager &SourceMgr;
+  FileID ID;
+  const FormatStyle &Style;
+  IdentifierTable IdentTable;
+  AdditionalKeywords Keywords;
+  encoding::Encoding Encoding;
+  llvm::SpecificBumpPtrAllocator<FormatToken> Allocator;
+  // Index (in 'Tokens') of the last token that starts a new line.
+  unsigned FirstInLineIndex;
+  SmallVector<FormatToken *, 16> Tokens;
+  SmallVector<IdentifierInfo *, 8> ForEachMacros;
+
+  bool FormattingDisabled;
+
+  llvm::Regex MacroBlockBeginRegex;
+  llvm::Regex MacroBlockEndRegex;
+
+  void readRawToken(FormatToken &Tok);
+
+  void resetLexer(unsigned Offset);
+};
+
+} // namespace format
+} // namespace clang
+
+#endif

lib/Format/FormatTokenLexer.cpp

+//===--- FormatTokenLexer.cpp - Lex FormatTokens -------------*- C++ ----*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file implements FormatTokenLexer, which tokenizes a source file
+/// into a FormatToken stream suitable for ClangFormat.
+///
+//===----------------------------------------------------------------------===//
+
+#include "FormatTokenLexer.h"
+#include "FormatToken.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Format/Format.h"
+#include "llvm/Support/Regex.h"
+
+namespace clang {
+namespace format {
+
+FormatTokenLexer::FormatTokenLexer(const SourceManager &SourceMgr, FileID ID,
+                                   const FormatStyle &Style,
+                                   encoding::Encoding Encoding)
+    : FormatTok(nullptr), IsFirstToken(true), GreaterStashed(false),
+      LessStashed(false), Column(0), TrailingWhitespace(0),
+      SourceMgr(SourceMgr), ID(ID), Style(Style),
+      IdentTable(getFormattingLangOpts(Style)), Keywords(IdentTable),
+      Encoding(Encoding), FirstInLineIndex(0), FormattingDisabled(false),
+      MacroBlockBeginRegex(Style.MacroBlockBegin),
+      MacroBlockEndRegex(Style.MacroBlockEnd) {
+  Lex.reset(new Lexer(ID, SourceMgr.getBuffer(ID), SourceMgr,
+                      getFormattingLangOpts(Style)));
+  Lex->SetKeepWhitespaceMode(true);
+
+  for (const std::string &ForEachMacro : Style.ForEachMacros)
+    ForEachMacros.push_back(&IdentTable.get(ForEachMacro));
+  std::sort(ForEachMacros.begin(), ForEachMacros.end());
+}
+
+ArrayRef<FormatToken *> FormatTokenLexer::lex() {
+  assert(Tokens.empty());
+  assert(FirstInLineIndex == 0);
+  do {
+    Tokens.push_back(getNextToken());
+    if (Style.Language == FormatStyle::LK_JavaScript)
+      tryParseJSRegexLiteral();
+    tryMergePreviousTokens();
+    if (Tokens.back()->NewlinesBefore > 0 || Tokens.back()->IsMultiline)
+      FirstInLineIndex = Tokens.size() - 1;
+  } while (Tokens.back()->Tok.isNot(tok::eof));
+  return Tokens;
+}
+
+void FormatTokenLexer::tryMergePreviousTokens() {
+  if (tryMerge_TMacro())
+    return;
+  if (tryMergeConflictMarkers())
+    return;
+  if (tryMergeLessLess())
+    return;
+
+  if (Style.Language == FormatStyle::LK_JavaScript) {
+    if (tryMergeTemplateString())
+      return;
+
+    static const tok::TokenKind JSIdentity[] = {tok::equalequal, tok::equal};
+    static const tok::TokenKind JSNotIdentity[] = {tok::exclaimequal,
+                                                   tok::equal};
+    static const tok::TokenKind JSShiftEqual[] = {tok::greater, tok::greater,
+                                                  tok::greaterequal};
+    static const tok::TokenKind JSRightArrow[] = {tok::equal, tok::greater};
+    // FIXME: Investigate what token type gives the correct operator priority.
+    if (tryMergeTokens(JSIdentity, TT_BinaryOperator))
+      return;
+    if (tryMergeTokens(JSNotIdentity, TT_BinaryOperator))
+      return;
+    if (tryMergeTokens(JSShiftEqual, TT_BinaryOperator))
+      return;
+    if (tryMergeTokens(JSRightArrow, TT_JsFatArrow))
+      return;
+  }
+}
+
+bool FormatTokenLexer::tryMergeLessLess() {
+  // Merge X,less,less,Y into X,lessless,Y unless X or Y is less.
+  if (Tokens.size() < 3)
+    return false;
+
+  bool FourthTokenIsLess = false;
+  if (Tokens.size() > 3)
+    FourthTokenIsLess = (Tokens.end() - 4)[0]->is(tok::less);
+
+  auto First = Tokens.end() - 3;
+  if (First[2]->is(tok::less) || First[1]->isNot(tok::less) ||
+      First[0]->isNot(tok::less) || FourthTokenIsLess)
+    return false;
+
+  // Only merge if there currently is no whitespace between the two "<".
+  if (First[1]->WhitespaceRange.getBegin() !=
+      First[1]->WhitespaceRange.getEnd())
+    return false;
+
+  First[0]->Tok.setKind(tok::lessless);
+  First[0]->TokenText = "<<";
+  First[0]->ColumnWidth += 1;
+  Tokens.erase(Tokens.end() - 2);
+  return true;
+}
+
+bool FormatTokenLexer::tryMergeTokens(ArrayRef<tok::TokenKind> Kinds,
+                                      TokenType NewType) {
+  if (Tokens.size() < Kinds.size())
+    return false;
+
+  SmallVectorImpl<FormatToken *>::const_iterator First =
+      Tokens.end() - Kinds.size();
+  if (!First[0]->is(Kinds[0]))
+    return false;
+  unsigned AddLength = 0;
+  for (unsigned i = 1; i < Kinds.size(); ++i) {
+    if (!First[i]->is(Kinds[i]) ||
+        First[i]->WhitespaceRange.getBegin() !=
+            First[i]->WhitespaceRange.getEnd())
+      return false;
+    AddLength += First[i]->TokenText.size();
+  }
+  Tokens.resize(Tokens.size() - Kinds.size() + 1);
+  First[0]->TokenText = StringRef(First[0]->TokenText.data(),
+                                  First[0]->TokenText.size() + AddLength);
+  First[0]->ColumnWidth += AddLength;
+  First[0]->Type = NewType;
+  return true;
+}
+
+// Returns \c true if \p Tok can only be followed by an operand in JavaScript.
+bool FormatTokenLexer::precedesOperand(FormatToken *Tok) {
+  // NB: This is not entirely correct, as an r_paren can introduce an operand
+  // location in e.g. `if (foo) /bar/.exec(...);`. That is a rare enough
+  // corner case to not matter in practice, though.
+  return Tok->isOneOf(tok::period, tok::l_paren, tok::comma, tok::l_brace,
+                      tok::r_brace, tok::l_square, tok::semi, tok::exclaim,
+                      tok::colon, tok::question, tok::tilde) ||
+         Tok->isOneOf(tok::kw_return, tok::kw_do, tok::kw_case, tok::kw_throw,
+                      tok::kw_else, tok::kw_new, tok::kw_delete, tok::kw_void,
+                      tok::kw_typeof, Keywords.kw_instanceof, Keywords.kw_in) ||
+         Tok->isBinaryOperator();
+}
+
+bool FormatTokenLexer::canPrecedeRegexLiteral(FormatToken *Prev) {
+  if (!Prev)
+    return true;
+
+  // Regex literals can only follow after prefix unary operators, not after
+  // postfix unary operators. If the '++' is followed by a non-operand
+  // introducing token, the slash here is the operand and not the start of a
+  // regex.
+  if (Prev->isOneOf(tok::plusplus, tok::minusminus))
+    return (Tokens.size() < 3 || precedesOperand(Tokens[Tokens.size() - 3]));
+
+  // The previous token must introduce an operand location where regex
+  // literals can occur.
+  if (!precedesOperand(Prev))
+    return false;
+
+  return true;
+}
+
+// Tries to parse a JavaScript Regex literal starting at the current token,
+// if that begins with a slash and is in a location where JavaScript allows
+// regex literals. Changes the current token to a regex literal and updates
+// its text if successful.
+void FormatTokenLexer::tryParseJSRegexLiteral() {
+  FormatToken *RegexToken = Tokens.back();
+  if (!RegexToken->isOneOf(tok::slash, tok::slashequal))
+    return;
+
+  FormatToken *Prev = nullptr;
+  for (auto I = Tokens.rbegin() + 1, E = Tokens.rend(); I != E; ++I) {
+    // NB: Because previous pointers are not initialized yet, this cannot use
+    // Token.getPreviousNonComment.
+    if ((*I)->isNot(tok::comment)) {
+      Prev = *I;
+      break;
+    }
+  }
+
+  if (!canPrecedeRegexLiteral(Prev))
+    return;
+
+  // 'Manually' lex ahead in the current file buffer.
+  const char *Offset = Lex->getBufferLocation();
+  const char *RegexBegin = Offset - RegexToken->TokenText.size();
+  StringRef Buffer = Lex->getBuffer();
+  bool InCharacterClass = false;
+  bool HaveClosingSlash = false;
+  for (; !HaveClosingSlash && Offset != Buffer.end(); ++Offset) {
+    // Regular expressions are terminated with a '/', which can only be
+    // escaped using '\' or a character class between '[' and ']'.
+    // See http://www.ecma-international.org/ecma-262/5.1/#sec-7.8.5.
+    switch (*Offset) {
+    case '\\':
+      // Skip the escaped character.
+      ++Offset;
+      break;
+    case '[':
+      InCharacterClass = true;
+      break;
+    case ']':
+      InCharacterClass = false;
+      break;
+    case '/':
+      if (!InCharacterClass)
+        HaveClosingSlash = true;
+      break;
+    }
+  }
+
+  RegexToken->Type = TT_RegexLiteral;
+  // Treat regex literals like other string_literals.
+  RegexToken->Tok.setKind(tok::string_literal);
+  RegexToken->TokenText = StringRef(RegexBegin, Offset - RegexBegin);
+  RegexToken->ColumnWidth = RegexToken->TokenText.size();
+
+  resetLexer(SourceMgr.getFileOffset(Lex->getSourceLocation(Offset)));
+}
+
+bool FormatTokenLexer::tryMergeTemplateString() {
+  if (Tokens.size() < 2)
+    return false;
+
+  FormatToken *EndBacktick = Tokens.back();
+  // Backticks get lexed as tok::unknown tokens. If a template string contains
+  // a comment start, it gets lexed as a tok::comment, or tok::unknown if
+  // unterminated.
+  if (!EndBacktick->isOneOf(tok::comment, tok::string_literal,
+                            tok::char_constant, tok::unknown))
+    return false;
+  size_t CommentBacktickPos = EndBacktick->TokenText.find('`');
+  // Unknown token that's not actually a backtick, or a comment that doesn't
+  // contain a backtick.
+  if (CommentBacktickPos == StringRef::npos)
+    return false;
+
+  unsigned TokenCount = 0;
+  bool IsMultiline = false;
+  unsigned EndColumnInFirstLine =
+      EndBacktick->OriginalColumn + EndBacktick->ColumnWidth;
+  for (auto I = Tokens.rbegin() + 1, E = Tokens.rend(); I != E; I++) {
+    ++TokenCount;
+    if (I[0]->IsMultiline)
+      IsMultiline = true;
+
+    // If there was a preceding template string, this must be the start of a
+    // template string, not the end.
+    if (I[0]->is(TT_TemplateString))
+      return false;
+
+    if (I[0]->isNot(tok::unknown) || I[0]->TokenText != "`") {
+      // Keep track of the rhs offset of the last token to wrap across lines -
+      // its the rhs offset of the first line of the template string, used to
+      // determine its width.
+      if (I[0]->IsMultiline)
+        EndColumnInFirstLine = I[0]->OriginalColumn + I[0]->ColumnWidth;
+      // If the token has newlines, the token before it (if it exists) is the
+      // rhs end of the previous line.
+      if (I[0]->NewlinesBefore > 0 && (I + 1 != E)) {
+        EndColumnInFirstLine = I[1]->OriginalColumn + I[1]->ColumnWidth;
+        IsMultiline = true;
+      }
+      continue;
+    }
+
+    Tokens.resize(Tokens.size() - TokenCount);
+    Tokens.back()->Type = TT_TemplateString;
+    const char *EndOffset =
+        EndBacktick->TokenText.data() + 1 + CommentBacktickPos;
+    if (CommentBacktickPos != 0) {
+      // If the backtick was not the first character (e.g. in a comment),
+      // re-lex after the backtick position.
+      SourceLocation Loc = EndBacktick->Tok.getLocation();
+      resetLexer(SourceMgr.getFileOffset(Loc) + CommentBacktickPos + 1);
+    }
+    Tokens.back()->TokenText =
+        StringRef(Tokens.back()->TokenText.data(),
+                  EndOffset - Tokens.back()->TokenText.data());
+
+    unsigned EndOriginalColumn = EndBacktick->OriginalColumn;
+    if (EndOriginalColumn == 0) {
+      SourceLocation Loc = EndBacktick->Tok.getLocation();
+      EndOriginalColumn = SourceMgr.getSpellingColumnNumber(Loc);
+    }
+    // If the ` is further down within the token (e.g. in a comment).
+    EndOriginalColumn += CommentBacktickPos;
+
+    if (IsMultiline) {
+      // ColumnWidth is from backtick to last token in line.
+      // LastLineColumnWidth is 0 to backtick.
+      // x = `some content
+      //     until here`;
+      Tokens.back()->ColumnWidth =
+          EndColumnInFirstLine - Tokens.back()->OriginalColumn;
+      // +1 for the ` itself.
+      Tokens.back()->LastLineColumnWidth = EndOriginalColumn + 1;
+      Tokens.back()->IsMultiline = true;
+    } else {
+      // Token simply spans from start to end, +1 for the ` itself.
+      Tokens.back()->ColumnWidth =
+          EndOriginalColumn - Tokens.back()->OriginalColumn + 1;
+    }
+    return true;
+  }
+  return false;
+}
+
+bool FormatTokenLexer::tryMerge_TMacro() {
+  if (Tokens.size() < 4)
+    return false;
+  FormatToken *Last = Tokens.back();
+  if (!Last->is(tok::r_paren))
+    return false;
+
+  FormatToken *String = Tokens[Tokens.size() - 2];
+  if (!String->is(tok::string_literal) || String->IsMultiline)
+    return false;
+
+  if (!Tokens[Tokens.size() - 3]->is(tok::l_paren))
+    return false;
+
+  FormatToken *Macro = Tokens[Tokens.size() - 4];
+  if (Macro->TokenText != "_T")
+    return false;
+
+  const char *Start = Macro->TokenText.data();
+  const char *End = Last->TokenText.data() + Last->TokenText.size();
+  String->TokenText = StringRef(Start, End - Start);
+  String->IsFirst = Macro->IsFirst;
+  String->LastNewlineOffset = Macro->LastNewlineOffset;
+  String->WhitespaceRange = Macro->WhitespaceRange;
+  String->OriginalColumn = Macro->OriginalColumn;
+  String->ColumnWidth = encoding::columnWidthWithTabs(
+      String->TokenText, String->OriginalColumn, Style.TabWidth, Encoding);
+  String->NewlinesBefore = Macro->NewlinesBefore;
+  String->HasUnescapedNewline = Macro->HasUnescapedNewline;
+
+  Tokens.pop_back();
+  Tokens.pop_back();
+  Tokens.pop_back();
+  Tokens.back() = String;
+  return true;
+}
+
+bool FormatTokenLexer::tryMergeConflictMarkers() {
+  if (Tokens.back()->NewlinesBefore == 0 && Tokens.back()->isNot(tok::eof))
+    return false;
+
+  // Conflict lines look like:
+  // <marker> <text from the vcs>
+  // For example:
+  // >>>>>>> /file/in/file/system at revision 1234
+  //
+  // We merge all tokens in a line that starts with a conflict marker
+  // into a single token with a special token type that the unwrapped line
+  // parser will use to correctly rebuild the underlying code.
+
+  FileID ID;
+  // Get the position of the first token in the line.
+  unsigned FirstInLineOffset;
+  std::tie(ID, FirstInLineOffset) = SourceMgr.getDecomposedLoc(
+      Tokens[FirstInLineIndex]->getStartOfNonWhitespace());
+  StringRef Buffer = SourceMgr.getBuffer(ID)->getBuffer();
+  // Calculate the offset of the start of the current line.
+  auto LineOffset = Buffer.rfind('\n', FirstInLineOffset);
+  if (LineOffset == StringRef::npos) {
+    LineOffset = 0;
+  } else {
+    ++LineOffset;
+  }
+
+  auto FirstSpace = Buffer.find_first_of(" \n", LineOffset);
+  StringRef LineStart;
+  if (FirstSpace == StringRef::npos) {
+    LineStart = Buffer.substr(LineOffset);
+  } else {
+    LineStart = Buffer.substr(LineOffset, FirstSpace - LineOffset);
+  }
+
+  TokenType Type = TT_Unknown;
+  if (LineStart == "<<<<<<<" || LineStart == ">>>>") {
+    Type = TT_ConflictStart;
+  } else if (LineStart == "|||||||" || LineStart == "=======" ||
+             LineStart == "====") {
+    Type = TT_ConflictAlternative;
+  } else if (LineStart == ">>>>>>>" || LineStart == "<<<<") {
+    Type = TT_ConflictEnd;
+  }
+
+  if (Type != TT_Unknown) {
+    FormatToken *Next = Tokens.back();
+
+    Tokens.resize(FirstInLineIndex + 1);
+    // We do not need to build a complete token here, as we will skip it
+    // during parsing anyway (as we must not touch whitespace around conflict
+    // markers).
+    Tokens.back()->Type = Type;
+    Tokens.back()->Tok.setKind(tok::kw___unknown_anytype);
+
+    Tokens.push_back(Next);
+    return true;
+  }
+
+  return false;
+}
+
+FormatToken *FormatTokenLexer::getStashedToken() {
+  // Create a synthesized second '>' or '<' token.
+  Token Tok = FormatTok->Tok;
+  StringRef TokenText = FormatTok->TokenText;
+
+  unsigned OriginalColumn = FormatTok->OriginalColumn;
+  FormatTok = new (Allocator.Allocate()) FormatToken;
+  FormatTok->Tok = Tok;
+  SourceLocation TokLocation =
+      FormatTok->Tok.getLocation().getLocWithOffset(Tok.getLength() - 1);
+  FormatTok->Tok.setLocation(TokLocation);
+  FormatTok->WhitespaceRange = SourceRange(TokLocation, TokLocation);
+  FormatTok->TokenText = TokenText;
+  FormatTok->ColumnWidth = 1;
+  FormatTok->OriginalColumn = OriginalColumn + 1;
+
+  return FormatTok;
+}
+
+FormatToken *FormatTokenLexer::getNextToken() {
+  if (GreaterStashed) {
+    GreaterStashed = false;
+    return getStashedToken();
+  }
+  if (LessStashed) {
+    LessStashed = false;
+    return getStashedToken();
+  }
+
+  FormatTok = new (Allocator.Allocate()) FormatToken;
+  readRawToken(*FormatTok);
+  SourceLocation WhitespaceStart =
+      FormatTok->Tok.getLocation().getLocWithOffset(-TrailingWhitespace);
+  FormatTok->IsFirst = IsFirstToken;
+  IsFirstToken = false;
+
+  // Consume and record whitespace until we find a significant token.
+  unsigned WhitespaceLength = TrailingWhitespace;
+  while (FormatTok->Tok.is(tok::unknown)) {
+    StringRef Text = FormatTok->TokenText;
+    auto EscapesNewline = [&](int pos) {
+      // A '\r' here is just part of '\r\n'. Skip it.
+      if (pos >= 0 && Text[pos] == '\r')
+        --pos;
+      // See whether there is an odd number of '\' before this.
+      unsigned count = 0;
+      for (; pos >= 0; --pos, ++count)
+        if (Text[pos] != '\\')
+          break;
+      return count & 1;
+    };
+    // FIXME: This miscounts tok:unknown tokens that are not just
+    // whitespace, e.g. a '`' character.
+    for (int i = 0, e = Text.size(); i != e; ++i) {
+      switch (Text[i]) {
+      case '\n':
+        ++FormatTok->NewlinesBefore;
+        FormatTok->HasUnescapedNewline = !EscapesNewline(i - 1);
+        FormatTok->LastNewlineOffset = WhitespaceLength + i + 1;
+        Column = 0;
+        break;
+      case '\r':
+        FormatTok->LastNewlineOffset = WhitespaceLength + i + 1;
+        Column = 0;
+        break;
+      case '\f':
+      case '\v':
+        Column = 0;
+        break;
+      case ' ':
+        ++Column;
+        break;
+      case '\t':
+        Column += Style.TabWidth - Column % Style.TabWidth;
+        break;
+      case '\\':
+        if (i + 1 == e || (Text[i + 1] != '\r' && Text[i + 1] != '\n'))
+          FormatTok->Type = TT_ImplicitStringLiteral;
+        break;
+      default:
+        FormatTok->Type = TT_ImplicitStringLiteral;
+        break;
+      }
+      if (FormatTok->Type == TT_ImplicitStringLiteral)
+        break;
+    }
+
+    if (FormatTok->is(TT_ImplicitStringLiteral))
+      break;
+    WhitespaceLength += FormatTok->Tok.getLength();
+
+    readRawToken(*FormatTok);
+  }
+
+  // In case the token starts with escaped newlines, we want to
+  // take them into account as whitespace - this pattern is quite frequent
+  // in macro definitions.
+  // FIXME: Add a more explicit test.
+  while (FormatTok->TokenText.size() > 1 && FormatTok->TokenText[0] == '\\' &&
+         FormatTok->TokenText[1] == '\n') {
+    ++FormatTok->NewlinesBefore;
+    WhitespaceLength += 2;
+    FormatTok->LastNewlineOffset = 2;
+    Column = 0;
+    FormatTok->TokenText = FormatTok->TokenText.substr(2);
+  }
+
+  FormatTok->WhitespaceRange = SourceRange(
+      WhitespaceStart, WhitespaceStart.getLocWithOffset(WhitespaceLength));
+
+  FormatTok->OriginalColumn = Column;
+
+  TrailingWhitespace = 0;
+  if (FormatTok->Tok.is(tok::comment)) {
+    // FIXME: Add the trimmed whitespace to Column.
+    StringRef UntrimmedText = FormatTok->TokenText;
+    FormatTok->TokenText = FormatTok->TokenText.rtrim(" \t\v\f");
+    TrailingWhitespace = UntrimmedText.size() - FormatTok->TokenText.size();
+  } else if (FormatTok->Tok.is(tok::raw_identifier)) {
+    IdentifierInfo &Info = IdentTable.get(FormatTok->TokenText);
+    FormatTok->Tok.setIdentifierInfo(&Info);
+    FormatTok->Tok.setKind(Info.getTokenID());
+    if (Style.Language == FormatStyle::LK_Java &&
+        FormatTok->isOneOf(tok::kw_struct, tok::kw_union, tok::kw_delete,
+                           tok::kw_operator)) {
+      FormatTok->Tok.setKind(tok::identifier);
+      FormatTok->Tok.setIdentifierInfo(nullptr);
+    } else if (Style.Language == FormatStyle::LK_JavaScript &&
+               FormatTok->isOneOf(tok::kw_struct, tok::kw_union,
+                                  tok::kw_operator)) {
+      FormatTok->Tok.setKind(tok::identifier);
+      FormatTok->Tok.setIdentifierInfo(nullptr);
+    }
+  } else if (FormatTok->Tok.is(tok::greatergreater)) {
+    FormatTok->Tok.setKind(tok::greater);
+    FormatTok->TokenText = FormatTok->TokenText.substr(0, 1);
+    GreaterStashed = true;
+  } else if (FormatTok->Tok.is(tok::lessless)) {
+    FormatTok->Tok.setKind(tok::less);
+    FormatTok->TokenText = FormatTok->TokenText.substr(0, 1);
+    LessStashed = true;
+  }
+
+  // Now FormatTok is the next non-whitespace token.
+
+  StringRef Text = FormatTok->TokenText;
+  size_t FirstNewlinePos = Text.find('\n');
+  if (FirstNewlinePos == StringRef::npos) {
+    // FIXME: ColumnWidth actually depends on the start column, we need to
+    // take this into account when the token is moved.
+    FormatTok->ColumnWidth =
+        encoding::columnWidthWithTabs(Text, Column, Style.TabWidth, Encoding);
+    Column += FormatTok->ColumnWidth;
+  } else {
+    FormatTok->IsMultiline = true;
+    // FIXME: ColumnWidth actually depends on the start column, we need to
+    // take this into account when the token is moved.
+    FormatTok->ColumnWidth = encoding::columnWidthWithTabs(
+        Text.substr(0, FirstNewlinePos), Column, Style.TabWidth, Encoding);
+
+    // The last line of the token always starts in column 0.
+    // Thus, the length can be precomputed even in the presence of tabs.
+    FormatTok->LastLineColumnWidth = encoding::columnWidthWithTabs(
+        Text.substr(Text.find_last_of('\n') + 1), 0, Style.TabWidth, Encoding);
+    Column = FormatTok->LastLineColumnWidth;
+  }
+
+  if (Style.Language == FormatStyle::LK_Cpp) {
+    if (!(Tokens.size() > 0 && Tokens.back()->Tok.getIdentifierInfo() &&
+          Tokens.back()->Tok.getIdentifierInfo()->getPPKeywordID() ==
+              tok::pp_define) &&
+        std::find(ForEachMacros.begin(), ForEachMacros.end(),
+                  FormatTok->Tok.getIdentifierInfo()) != ForEachMacros.end()) {
+      FormatTok->Type = TT_ForEachMacro;
+    } else if (FormatTok->is(tok::identifier)) {
+      if (MacroBlockBeginRegex.match(Text)) {
+        FormatTok->Type = TT_MacroBlockBegin;
+      } else if (MacroBlockEndRegex.match(Text)) {
+        FormatTok->Type = TT_MacroBlockEnd;
+      }
+    }
+  }
+
+  return FormatTok;
+}
+
+void FormatTokenLexer::readRawToken(FormatToken &Tok) {
+  Lex->LexFromRawLexer(Tok.Tok);
+  Tok.TokenText = StringRef(SourceMgr.getCharacterData(Tok.Tok.getLocation()),
+                            Tok.Tok.getLength());
+  // For formatting, treat unterminated string literals like normal string
+  // literals.
+  if (Tok.is(tok::unknown)) {
+    if (!Tok.TokenText.empty() && Tok.TokenText[0] == '"') {
+      Tok.Tok.setKind(tok::string_literal);
+      Tok.IsUnterminatedLiteral = true;
+    } else if (Style.Language == FormatStyle::LK_JavaScript &&
+               Tok.TokenText == "''") {
+      Tok.Tok.setKind(tok::string_literal);
+    }
+  }
+
+  if (Style.Language == FormatStyle::LK_JavaScript &&
+      Tok.is(tok::char_constant)) {
+    Tok.Tok.setKind(tok::string_literal);
+  }
+
+  if (Tok.is(tok::comment) && (Tok.TokenText == "// clang-format on" ||
+                               Tok.TokenText == "/* clang-format on */")) {
+    FormattingDisabled = false;
+  }
+
+  Tok.Finalized = FormattingDisabled;
+
+  if (Tok.is(tok::comment) && (Tok.TokenText == "// clang-format off" ||
+                               Tok.TokenText == "/* clang-format off */")) {
+    FormattingDisabled = true;
+  }
+}
+
+void FormatTokenLexer::resetLexer(unsigned Offset) {
+  StringRef Buffer = SourceMgr.getBufferData(ID);
+  Lex.reset(new Lexer(SourceMgr.getLocForStartOfFile(ID),
+                      getFormattingLangOpts(Style), Buffer.begin(),
+                      Buffer.begin() + Offset, Buffer.end()));
+  Lex->SetKeepWhitespaceMode(true);
+  TrailingWhitespace = 0;
+}
+
+} // namespace format
+} // namespace clang

lib/Format/SortJavaScriptImports.h

+//===--- SortJavaScriptImports.h - Sort ES6 Imports -------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file implements a sorter for JavaScript ES6 imports.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_LIB_FORMAT_SORTJAVASCRIPTIMPORTS_H
+#define LLVM_CLANG_LIB_FORMAT_SORTJAVASCRIPTIMPORTS_H
+
+#include "clang/Basic/LLVM.h"
+#include "clang/Format/Format.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringRef.h"
+
+namespace clang {
+namespace format {
+
+// Sort JavaScript ES6 imports/exports in ``Code``.
+tooling::Replacements sortJavaScriptImports(const FormatStyle &Style,
+                                            StringRef Code,
+                                            ArrayRef<tooling::Range> Ranges,
+                                            StringRef FileName);
+
+} // end namespace format
+} // end namespace clang
+
+#endif

lib/Format/SortJavaScriptImports.cpp

+//===--- SortJavaScriptImports.h - Sort ES6 Imports -------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file implements a sort operation for JavaScript ES6 imports.
+///
+//===----------------------------------------------------------------------===//
+
+#include "SortJavaScriptImports.h"
+#include "SortJavaScriptImports.h"
+#include "TokenAnalyzer.h"
+#include "TokenAnnotator.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/DiagnosticOptions.h"
+#include "clang/Basic/LLVM.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Format/Format.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/Debug.h"
+#include <string>
+
+#define DEBUG_TYPE "format-formatter"
+
+namespace clang {
+namespace format {
+
+class FormatTokenLexer;
+
+using clang::format::FormatStyle;
+
+// An imported symbol in a JavaScript ES6 import/export, possibly aliased.
+struct JsImportedSymbol {
+  StringRef Symbol;
+  StringRef Alias;
+};
+
+struct JsImportExport {
+  bool IsExport;
+  // JS imports are sorted into these categories, in order.
+  enum JsImportCategory {
+    ABSOLUTE,        // from 'something'
+    RELATIVE_PARENT, // from '../*'
+    RELATIVE,        // from './*'
+  };
+  JsImportCategory Category;
+  // The URL imported, e.g. `import .. from 'url';`. Empty for `export {a, b};`.
+  StringRef URL;
+  // Prefix from "import * as prefix". Empty for symbol imports. Implies an
+  // empty names list.
+  StringRef Prefix;
+  // Symbols from `import {SymbolA, SymbolB, ...} from ...;`.
+  SmallVector<JsImportedSymbol, 1> Symbols;
+  // Textual position of the import/export, including preceding and trailing
+  // comments.
+  SourceLocation Start;
+  SourceLocation End;
+};
+
+bool operator<(const JsImportExport &LHS, const JsImportExport &RHS) {
+  if (LHS.IsExport != RHS.IsExport)
+    return LHS.IsExport < RHS.IsExport;
+  if (LHS.Category != RHS.Category)
+    return LHS.Category < RHS.Category;
+  // NB: empty URLs sort *last* (for export {...};).
+  if (LHS.URL.empty() != RHS.URL.empty())
+    return LHS.URL.empty() < RHS.URL.empty();
+  if (LHS.URL != RHS.URL)
+    return LHS.URL < RHS.URL;
+  // NB: '*' imports (with prefix) sort before {a, b, ...} imports.
+  if (LHS.Prefix.empty() != RHS.Prefix.empty())
+    return LHS.Prefix.empty() < RHS.Prefix.empty();
+  if (LHS.Prefix != RHS.Prefix)
+    return LHS.Prefix > RHS.Prefix;
+  return false;
+}
+
+// JavaScriptImportSorter sorts JavaScript ES6 imports and exports. It is
+// implemented as a TokenAnalyzer because ES6 imports have substantial syntactic
+// structure, making it messy to sort them using regular expressions.
+class JavaScriptImportSorter : public TokenAnalyzer {
+public:
+  JavaScriptImportSorter(const Environment &Env, const FormatStyle &Style)
+      : TokenAnalyzer(Env, Style),
+        FileContents(Env.getSourceManager().getBufferData(Env.getFileID())) {}
+
+  tooling::Replacements
+  analyze(TokenAnnotator &Annotator,
+          SmallVectorImpl<AnnotatedLine *> &AnnotatedLines,
+          FormatTokenLexer &Tokens, tooling::Replacements &Result) override {
+    AffectedRangeMgr.computeAffectedLines(AnnotatedLines.begin(),
+                                          AnnotatedLines.end());
+
+    const AdditionalKeywords &Keywords = Tokens.getKeywords();
+
+    SmallVector<JsImportExport, 16> Imports;
+    SourceLocation LastStart;
+    for (auto Line : AnnotatedLines) {
+      if (!Line->Affected)
+        break;
+      Current = Line->First;
+      LineEnd = Line->Last;
+      JsImportExport ImpExp;
+      skipComments();
+      if (LastStart.isInvalid() || Imports.empty())
+        // After the first file level comment, consider line comments to be part
+        // of the import that immediately follows them by using the previously
+        // set LastStart.
+        LastStart = Line->First->Tok.getLocation();
+      if (!Current)
+        continue; // Only comments on this line.
+      ImpExp.Start = LastStart;
+      LastStart = SourceLocation();
+      if (!parseImportExport(Keywords, ImpExp))
+        break;
+      ImpExp.End = LineEnd->Tok.getEndLoc();
+      DEBUG({
+        llvm::dbgs() << "Import: {"
+                     << "is_export: " << ImpExp.IsExport
+                     << ", cat: " << ImpExp.Category << ", url: " << ImpExp.URL
+                     << ", prefix: " << ImpExp.Prefix;
+        for (size_t i = 0; i < ImpExp.Symbols.size(); ++i)
+          llvm::dbgs() << ", " << ImpExp.Symbols[i].Symbol << " as "
+                       << ImpExp.Symbols[i].Alias;
+        llvm::dbgs() << ", text: " << getSourceText(ImpExp.Start, ImpExp.End);
+        llvm::dbgs() << "}\n";
+      });
+      Imports.push_back(ImpExp);
+    }
+
+    if (Imports.empty())
+      return Result;
+
+    SmallVector<unsigned, 16> Indices;
+    for (unsigned i = 0, e = Imports.size(); i != e; ++i)
+      Indices.push_back(i);
+    std::stable_sort(Indices.begin(), Indices.end(),
+                     [&](unsigned LHSI, unsigned RHSI) {
+                       return Imports[LHSI] < Imports[RHSI];
+                     });
+    // FIXME: Pull this into a common function.
+    bool OutOfOrder = false;
+    for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
+      if (i != Indices[i]) {
+        OutOfOrder = true;
+        break;
+      }
+    }
+    if (!OutOfOrder)
+      return Result;
+
+    // Replace all existing import/export statements.
+    std::string ImportsText;
+    for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
+      JsImportExport ImpExp = Imports[Indices[i]];
+      StringRef ImportStmt = getSourceText(ImpExp.Start, ImpExp.End);
+      ImportsText += ImportStmt;
+      ImportsText += "\n";
+      // Separate groups outside of exports with two line breaks.
+      if (i + 1 < e && !ImpExp.IsExport &&
+          ImpExp.Category != Imports[Indices[i + 1]].Category)
+        ImportsText += "\n";
+    }
+    SourceLocation InsertionPoint = Imports[0].Start;
+    SourceLocation End = Imports[Imports.size() - 1].End;
+    DEBUG(llvm::dbgs() << "Replacing imports:\n"
+                       << getSourceText(InsertionPoint, End) << "\nwith:\n"
+                       << ImportsText);
+    Result.insert(tooling::Replacement(
+        Env.getSourceManager(),
+        CharSourceRange::getCharRange(InsertionPoint, End), ImportsText));
+
+    return Result;
+  }
+
+private:
+  FormatToken *Current;
+  FormatToken *LineEnd;
+  StringRef FileContents;
+
+  void skipComments() { Current = skipComments(Current); }
+
+  FormatToken *skipComments(FormatToken *Tok) {
+    while (Tok && Tok->is(tok::comment))
+      Tok = Tok->Next;
+    return Tok;
+  }
+
+  bool nextToken() {
+    Current = Current->Next;
+    skipComments();
+    return Current && Current != LineEnd->Next;
+  }
+
+  StringRef getSourceText(SourceLocation Start, SourceLocation End) {
+    const SourceManager &SM = Env.getSourceManager();
+    return FileContents.substr(SM.getFileOffset(Start),
+                               SM.getFileOffset(End) - SM.getFileOffset(Start));
+  }
+
+  bool parseImportExport(const AdditionalKeywords &Keywords,
+                         JsImportExport &ImpExp) {
+    if (!Current || !Current->isOneOf(Keywords.kw_import, tok::kw_export))
+      return false;
+    ImpExp.IsExport = Current->is(tok::kw_export);
+    nextToken();
+
+    if (!parseImportExportSpecifier(Keywords, ImpExp) || !nextToken())
+      return false;
+    if (Current->is(Keywords.kw_from)) {
+      // imports have a 'from' clause, exports might not.
+      if (!nextToken())
+        return false;
+      if (!Current->isStringLiteral())
+        return false;
+      // URL = TokenText without the quotes.
+      ImpExp.URL = Current->TokenText.substr(1, Current->TokenText.size() - 2);
+      if (ImpExp.URL.startswith(".."))
+        ImpExp.Category = JsImportExport::JsImportCategory::RELATIVE_PARENT;
+      else if (ImpExp.URL.startswith("."))
+        ImpExp.Category = JsImportExport::JsImportCategory::RELATIVE;
+      else
+        ImpExp.Category = JsImportExport::JsImportCategory::ABSOLUTE;
+    } else {
+      // w/o URL groups with "empty".
+      ImpExp.Category = JsImportExport::JsImportCategory::RELATIVE;
+    }
+    return true;
+  }
+
+  bool parseImportExportSpecifier(const AdditionalKeywords &Keywords,
+                                  JsImportExport &ImpExp) {
+    // * as prefix from '...';
+    if (Current->is(tok::star)) {
+      if (!nextToken())
+        return false;
+      if (!Current->is(Keywords.kw_as) || !nextToken())
+        return false;
+      if (!Current->is(tok::identifier))
+        return false;
+      ImpExp.Prefix = Current->TokenText;
+      return true;
+    }
+
+    if (!Current->is(tok::l_brace))
+      return false;
+
+    // {sym as alias, sym2 as ...} from '...';
+    if (!nextToken())
+      return false;
+    while (true) {
+      if (!Current->is(tok::identifier))
+        return false;
+
+      JsImportedSymbol Symbol;
+      Symbol.Symbol = Current->TokenText;
+      nextToken();
+
+      if (Current->is(Keywords.kw_as)) {
+        nextToken();
+        if (!Current->is(tok::identifier))
+          return false;
+        Symbol.Alias = Current->TokenText;
+        nextToken();
+      }
+      ImpExp.Symbols.push_back(Symbol);
+
+      if (Current->is(tok::r_brace))
+        return true;
+      if (!Current->is(tok::comma))
+        return false;
+      nextToken();
+    }
+  }
+};
+
+tooling::Replacements sortJavaScriptImports(const FormatStyle &Style,
+                                            StringRef Code,
+                                            ArrayRef<tooling::Range> Ranges,
+                                            StringRef FileName) {
+  // FIXME: Cursor support.
+  std::unique_ptr<Environment> Env =
+      Environment::CreateVirtualEnvironment(Code, FileName, Ranges);
+  JavaScriptImportSorter Sorter(*Env, Style);
+  return Sorter.process();
+}
+
+} // end namespace format
+} // end namespace clang

lib/Format/TokenAnalyzer.h

+//===--- TokenAnalyzer.h - Analyze Token Streams ----------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file declares an abstract TokenAnalyzer, and associated helper
+/// classes. TokenAnalyzer can be extended to generate replacements based on
+/// an annotated and pre-processed token stream.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_LIB_FORMAT_TOKENANALYZER_H
+#define LLVM_CLANG_LIB_FORMAT_TOKENANALYZER_H
+
+#include "AffectedRangeManager.h"
+#include "Encoding.h"
+#include "FormatToken.h"
+#include "FormatTokenLexer.h"
+#include "TokenAnnotator.h"
+#include "UnwrappedLineParser.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/DiagnosticOptions.h"
+#include "clang/Basic/FileManager.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Format/Format.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Debug.h"
+
+#define DEBUG_TYPE "format-formatter"
+
+namespace clang {
+namespace format {
+
+static StringRef getLanguageName(FormatStyle::LanguageKind Language) {
+  switch (Language) {
+  case FormatStyle::LK_Cpp:
+    return "C++";
+  case FormatStyle::LK_Java:
+    return "Java";
+  case FormatStyle::LK_JavaScript:
+    return "JavaScript";
+  case FormatStyle::LK_Proto:
+    return "Proto";
+  default:
+    return "Unknown";
+  }
+}
+
+class Environment {
+public:
+  Environment(SourceManager &SM, FileID ID, ArrayRef<CharSourceRange> Ranges)
+      : ID(ID), CharRanges(Ranges.begin(), Ranges.end()), SM(SM) {}
+
+  Environment(FileID ID, std::unique_ptr<FileManager> FileMgr,
+              std::unique_ptr<SourceManager> VirtualSM,
+              std::unique_ptr<DiagnosticsEngine> Diagnostics,
+              const std::vector<CharSourceRange> &CharRanges)
+      : ID(ID), CharRanges(CharRanges.begin(), CharRanges.end()),
+        SM(*VirtualSM), FileMgr(std::move(FileMgr)),
+        VirtualSM(std::move(VirtualSM)), Diagnostics(std::move(Diagnostics)) {}
+
+  // This sets up an virtual file system with file \p FileName containing \p
+  // Code.
+  static std::unique_ptr<Environment>
+  CreateVirtualEnvironment(StringRef Code, StringRef FileName,
+                           ArrayRef<tooling::Range> Ranges);
+
+  FileID getFileID() const { return ID; }
+
+  StringRef getFileName() const { return FileName; }
+
+  ArrayRef<CharSourceRange> getCharRanges() const { return CharRanges; }
+
+  const SourceManager &getSourceManager() const { return SM; }
+
+private:
+  FileID ID;
+  StringRef FileName;
+  SmallVector<CharSourceRange, 8> CharRanges;
+  SourceManager &SM;
+
+  // The order of these fields are important - they should be in the same order
+  // as they are created in `CreateVirtualEnvironment` so that they can be
+  // deleted in the reverse order as they are created.
+  std::unique_ptr<FileManager> FileMgr;
+  std::unique_ptr<SourceManager> VirtualSM;
+  std::unique_ptr<DiagnosticsEngine> Diagnostics;
+};
+
+class TokenAnalyzer : public UnwrappedLineConsumer {
+public:
+  TokenAnalyzer(const Environment &Env, const FormatStyle &Style);
+
+  tooling::Replacements process();
+
+protected:
+  virtual tooling::Replacements
+  analyze(TokenAnnotator &Annotator,
+          SmallVectorImpl<AnnotatedLine *> &AnnotatedLines,
+          FormatTokenLexer &Tokens, tooling::Replacements &Result) = 0;
+
+  void consumeUnwrappedLine(const UnwrappedLine &TheLine) override;
+
+  void finishRun() override;
+
+  FormatStyle Style;
+  // Stores Style, FileID and SourceManager etc.
+  const Environment &Env;
+  // AffectedRangeMgr stores ranges to be fixed.
+  AffectedRangeManager AffectedRangeMgr;
+  SmallVector<SmallVector<UnwrappedLine, 16>, 2> UnwrappedLines;
+  encoding::Encoding Encoding;
+};
+
+} // end namespace format
+} // end namespace clang
+
+#endif

lib/Format/TokenAnalyzer.cpp

+//===--- TokenAnalyzer.cpp - Analyze Token Streams --------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file implements an abstract TokenAnalyzer and associated helper
+/// classes. TokenAnalyzer can be extended to generate replacements based on
+/// an annotated and pre-processed token stream.
+///
+//===----------------------------------------------------------------------===//
+
+#include "TokenAnalyzer.h"
+#include "AffectedRangeManager.h"
+#include "Encoding.h"
+#include "FormatToken.h"
+#include "FormatTokenLexer.h"
+#include "TokenAnnotator.h"
+#include "UnwrappedLineParser.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/DiagnosticOptions.h"
+#include "clang/Basic/FileManager.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Format/Format.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Debug.h"
+
+#define DEBUG_TYPE "format-formatter"
+
+namespace clang {
+namespace format {
+
+// This sets up an virtual file system with file \p FileName containing \p
+// Code.
+std::unique_ptr<Environment>
+Environment::CreateVirtualEnvironment(StringRef Code, StringRef FileName,
+                                      ArrayRef<tooling::Range> Ranges) {
+  // This is referenced by `FileMgr` and will be released by `FileMgr` when it
+  // is deleted.
+  IntrusiveRefCntPtr<vfs::InMemoryFileSystem> InMemoryFileSystem(
+      new vfs::InMemoryFileSystem);
+  // This is passed to `SM` as reference, so the pointer has to be referenced
+  // in `Environment` so that `FileMgr` can out-live this function scope.
+  std::unique_ptr<FileManager> FileMgr(
+      new FileManager(FileSystemOptions(), InMemoryFileSystem));
+  // This is passed to `SM` as reference, so the pointer has to be referenced
+  // by `Environment` due to the same reason above.
+  std::unique_ptr<DiagnosticsEngine> Diagnostics(new DiagnosticsEngine(
+      IntrusiveRefCntPtr<DiagnosticIDs>(new DiagnosticIDs),
+      new DiagnosticOptions));
+  // This will be stored as reference, so the pointer has to be stored in
+  // due to the same reason above.
+  std::unique_ptr<SourceManager> VirtualSM(
+      new SourceManager(*Diagnostics, *FileMgr));
+  InMemoryFileSystem->addFile(
+      FileName, 0, llvm::MemoryBuffer::getMemBuffer(
+                       Code, FileName, /*RequiresNullTerminator=*/false));
+  FileID ID = VirtualSM->createFileID(FileMgr->getFile(FileName),
+                                      SourceLocation(), clang::SrcMgr::C_User);
+  assert(ID.isValid());
+  SourceLocation StartOfFile = VirtualSM->getLocForStartOfFile(ID);
+  std::vector<CharSourceRange> CharRanges;
+  for (const tooling::Range &Range : Ranges) {
+    SourceLocation Start = StartOfFile.getLocWithOffset(Range.getOffset());
+    SourceLocation End = Start.getLocWithOffset(Range.getLength());
+    CharRanges.push_back(CharSourceRange::getCharRange(Start, End));
+  }
+  return llvm::make_unique<Environment>(ID, std::move(FileMgr),
+                                        std::move(VirtualSM),
+                                        std::move(Diagnostics), CharRanges);
+}
+
+TokenAnalyzer::TokenAnalyzer(const Environment &Env, const FormatStyle &Style)
+    : Style(Style), Env(Env),
+      AffectedRangeMgr(Env.getSourceManager(), Env.getCharRanges()),
+      UnwrappedLines(1),
+      Encoding(encoding::detectEncoding(
+          Env.getSourceManager().getBufferData(Env.getFileID()))) {
+  DEBUG(
+      llvm::dbgs() << "File encoding: "
+                   << (Encoding == encoding::Encoding_UTF8 ? "UTF8" : "unknown")
+                   << "\n");
+  DEBUG(llvm::dbgs() << "Language: " << getLanguageName(Style.Language)
+                     << "\n");
+}
+
+tooling::Replacements TokenAnalyzer::process() {
+  tooling::Replacements Result;
+  FormatTokenLexer Tokens(Env.getSourceManager(), Env.getFileID(), Style,
+                          Encoding);
+
+  UnwrappedLineParser Parser(Style, Tokens.getKeywords(), Tokens.lex(), *this);
+  Parser.parse();
+  assert(UnwrappedLines.rbegin()->empty());
+  for (unsigned Run = 0, RunE = UnwrappedLines.size(); Run + 1 != RunE; ++Run) {
+    DEBUG(llvm::dbgs() << "Run " << Run << "...\n");
+    SmallVector<AnnotatedLine *, 16> AnnotatedLines;
+
+    TokenAnnotator Annotator(Style, Tokens.getKeywords());
+    for (unsigned i = 0, e = UnwrappedLines[Run].size(); i != e; ++i) {
+      AnnotatedLines.push_back(new AnnotatedLine(UnwrappedLines[Run][i]));
+      Annotator.annotate(*AnnotatedLines.back());
+    }
+
+    tooling::Replacements RunResult =
+        analyze(Annotator, AnnotatedLines, Tokens, Result);
+
+    DEBUG({
+      llvm::dbgs() << "Replacements for run " << Run << ":\n";
+      for (tooling::Replacements::iterator I = RunResult.begin(),
+                                           E = RunResult.end();
+           I != E; ++I) {
+        llvm::dbgs() << I->toString() << "\n";
+      }
+    });
+    for (unsigned i = 0, e = AnnotatedLines.size(); i != e; ++i) {
+      delete AnnotatedLines[i];
+    }
+    Result.insert(RunResult.begin(), RunResult.end());
+  }
+  return Result;
+}
+
+void TokenAnalyzer::consumeUnwrappedLine(const UnwrappedLine &TheLine) {
+  assert(!UnwrappedLines.empty());
+  UnwrappedLines.back().push_back(TheLine);
+}
+
+void TokenAnalyzer::finishRun() {
+  UnwrappedLines.push_back(SmallVector<UnwrappedLine, 16>());
+}
+
+} // end namespace format
+} // end namespace clang

unittests/Format/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Support
   )
 
 add_clang_unittest(FormatTests
   CleanupTest.cpp
   FormatTest.cpp
   FormatTestJava.cpp
   FormatTestJS.cpp
   FormatTestProto.cpp
   FormatTestSelective.cpp
+  SortImportsTestJS.cpp
   SortIncludesTest.cpp
   )
 
 target_link_libraries(FormatTests
   clangBasic
   clangFormat
   clangFrontend
   clangRewrite
   clangToolingCore
   )

unittests/Format/SortImportsTestJS.cpp

+//===- unittest/Format/SortImportsTestJS.cpp - JS import sort unit tests --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "FormatTestUtils.h"
+#include "clang/Format/Format.h"
+#include "llvm/Support/Debug.h"
+#include "gtest/gtest.h"
+
+#define DEBUG_TYPE "format-test"
+
+namespace clang {
+namespace format {
+namespace {
+
+class SortImportsTestJS : public ::testing::Test {
+protected:
+  std::vector<tooling::Range> GetCodeRange(StringRef Code) {
+    return std::vector<tooling::Range>(1, tooling::Range(0, Code.size()));
+  }
+
+  std::string sort(StringRef Code, StringRef FileName = "input.js") {
+    auto Ranges = GetCodeRange(Code);
+    std::string Sorted =
+        applyAllReplacements(Code, sortIncludes(Style, Code, Ranges, FileName));
+    return applyAllReplacements(Sorted,
+                                reformat(Style, Sorted, Ranges, FileName));
+  }
+
+  void verifySort(llvm::StringRef Expected, llvm::StringRef Code) {
+    std::string Result = sort(Code);
+    EXPECT_EQ(Expected.str(), Result) << "Formatted:\n" << Result;
+  }
+
+  FormatStyle Style = getGoogleStyle(FormatStyle::LK_JavaScript);
+};
+
+TEST_F(SortImportsTestJS, BasicSorting) {
+  verifySort("import {sym} from 'a';\n"
+             "import {sym} from 'b';\n"
+             "import {sym} from 'c';\n"
+             "\n"
+             "let x = 1;",
+             "import {sym} from 'a';\n"
+             "import {sym} from 'c';\n"
+             "import {sym} from 'b';\n"
+             "let x = 1;");
+}
+
+TEST_F(SortImportsTestJS, Comments) {
+  verifySort("/** @fileoverview This is a great file. */\n"
+             "// A very important import follows.\n"
+             "import {sym} from 'a'; /* more comments */\n"
+             "import {sym} from 'b'; // from //foo:bar\n",
+             "/** @fileoverview This is a great file. */\n"
+             "import {sym} from 'b'; // from //foo:bar\n"
+             "// A very important import follows.\n"
+             "import {sym} from 'a'; /* more comments */\n");
+}
+
+TEST_F(SortImportsTestJS, SortStar) {
+  verifySort("import * as foo from 'a';\n"
+             "import {sym} from 'a';\n"
+             "import * as bar from 'b';\n",
+             "import {sym} from 'a';\n"
+             "import * as foo from 'a';\n"
+             "import * as bar from 'b';\n");
+}
+
+TEST_F(SortImportsTestJS, AliasesSymbols) {
+  verifySort("import {sym1 as alias1} from 'b';\n"
+             "import {sym2 as alias2, sym3 as alias3} from 'c';\n",
+             "import {sym2 as alias2, sym3 as alias3} from 'c';\n"
+             "import {sym1 as alias1} from 'b';\n");
+}
+
+TEST_F(SortImportsTestJS, GroupImports) {
+  verifySort("import {a} from 'absolute';\n"
+             "\n"
+             "import {b} from '../parent';\n"
+             "import {b} from '../parent/nested';\n"
+             "\n"
+             "import {b} from './relative/path';\n"
+             "import {b} from './relative/path/nested';\n"
+             "\n"
+             "let x = 1;\n",
+             "import {b} from './relative/path/nested';\n"
+             "import {b} from './relative/path';\n"
+             "import {b} from '../parent/nested';\n"
+             "import {b} from '../parent';\n"
+             "import {a} from 'absolute';\n"
+             "let x = 1;\n");
+}
+
+TEST_F(SortImportsTestJS, Exports) {
+  verifySort("import {S} from 'bpath';\n"
+             "\n"
+             "import {T} from './cpath';\n"
+             "\n"
+             "export {A, B} from 'apath';\n"
+             "export {P} from '../parent';\n"
+             "export {R} from './relative';\n"
+             "export {S};\n"
+             "\n"
+             "let x = 1;\n"
+             "export y = 1;\n",
+             "export {R} from './relative';\n"
+             "import {T} from './cpath';\n"
+             "export {S};\n"
+             "export {A, B} from 'apath';\n"
+             "import {S} from 'bpath';\n"
+             "export {P} from '../parent';\n"
+             "let x = 1;\n"
+             "export y = 1;\n");
+}
+
+} // end namespace
+} // end namespace format
+} // end namespace clang