[clang-format] Recognize C# named argument colons as a token type

[jbcoe]

Summary

No longer merge 'name' and ':' into a single token.

Ensure that line breaks cannot be placed before or after a named-argument colon.

Ensure that no space is inserted before a named-argument colon.

[krasimir]

This is very nice! Brings the C# handling of the colon closer to other languages.

clang/lib/Format/TokenAnnotator.cpp

3499

nit: please put this as an else if into the "// Language-specific stuff" section below.

[jbcoe]

Consolidate if blocks following review comment.

clang/lib/Format/FormatToken.h

#define LIST_TOKEN_TYPES                                                       \
   TYPE(ProtoExtensionLSquare)                                                  \
   TYPE(TrailingAnnotation)                                                     \
   TYPE(TrailingReturnArrow)                                                    \
   TYPE(TrailingUnaryOperator)                                                  \
   TYPE(TypenameMacro)                                                          \
   TYPE(UnaryOperator)                                                          \
   TYPE(CSharpStringLiteral)                                                    \
   TYPE(CSharpNullCoalescing)                                                   \
-  TYPE(CSharpNamedArgument)                                                    \
+  TYPE(CSharpNamedArgumentColon)                                               \
   TYPE(Unknown)
 
 enum TokenType {
 #define TYPE(X) TT_##X,
   LIST_TOKEN_TYPES
 #undef TYPE
       NUM_TOKEN_TYPES
 };

clang/lib/Format/FormatTokenLexer.h

private:
   bool tryMergeNSStringLiteral();
   bool tryMergeJSPrivateIdentifier();
   bool tryMergeCSharpStringLiteral();
   bool tryMergeCSharpKeywordVariables();
   bool tryMergeCSharpNullConditionals();
   bool tryMergeCSharpDoubleQuestion();
   bool tryTransformCSharpForEach();
   bool tryMergeCSharpAttributeAndTarget();
-  bool tryMergeCSharpNamedArgument();
 
   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);
 

clang/lib/Format/FormatTokenLexer.cpp

void FormatTokenLexer::tryMergePreviousTokens() {
   if (tryMerge_TMacro())
     return;
   if (tryMergeConflictMarkers())
     return;
   if (tryMergeLessLess())
     return;
 
   if (Style.isCSharp()) {
-    if (tryMergeCSharpNamedArgument())
-      return;
     if (tryMergeCSharpAttributeAndTarget())
       return;
     if (tryMergeCSharpKeywordVariables())
       return;
     if (tryMergeCSharpStringLiteral())
       return;
     if (tryMergeCSharpDoubleQuestion())
       return;
Hash->TokenText =
       StringRef(Hash->TokenText.begin(),
                 Identifier->TokenText.end() - Hash->TokenText.begin());
   Hash->ColumnWidth += Identifier->ColumnWidth;
   Hash->Type = TT_JsPrivateIdentifier;
   Tokens.erase(Tokens.end() - 1);
   return true;
 }
 
-// Merge 'argName' and ':' into a single token in `foo(argName: bar)`.
-bool FormatTokenLexer::tryMergeCSharpNamedArgument() {
-  if (Tokens.size() < 2)
-    return false;
-  auto &Colon = *(Tokens.end() - 1);
-  if (!Colon->is(tok::colon))
-    return false;
-
-  auto &Name = *(Tokens.end() - 2);
-  if (!Name->is(tok::identifier))
-    return false;
-    
-  const FormatToken *CommaOrLeftParen = nullptr;
-  for (auto I = Tokens.rbegin() + 2, E = Tokens.rend(); I != E; ++I) {
-    // NB: Because previous pointers are not initialized yet, this cannot use
-    // Token.getPreviousNonComment.
-    if ((*I)->isNot(tok::comment)) {
-      CommaOrLeftParen = *I;
-      break;
-    }
-  }
-
-  if (!CommaOrLeftParen || !CommaOrLeftParen->isOneOf(tok::l_paren, tok::comma))
-    return false;
-
-  Name->TokenText = StringRef(Name->TokenText.begin(),
-                              Colon->TokenText.end() - Name->TokenText.begin());
-  Name->ColumnWidth += Colon->ColumnWidth;
-  Name->Type = TT_CSharpNamedArgument;
-  Tokens.erase(Tokens.end() - 1);
-  return true;
-}
-
 // Search for verbatim or interpolated string literals @"ABC" or
 // $"aaaaa{abc}aaaaa" i and mark the token as TT_CSharpStringLiteral, and to
 // prevent splitting of @, $ and ".
 // Merging of multiline verbatim strings with embedded '"' is handled in
 // handleCSharpVerbatimAndInterpolatedStrings with lower-level lexing.
 bool FormatTokenLexer::tryMergeCSharpStringLiteral() {
   if (Tokens.size() < 2)
     return false;
StringRef FirstLineText = FirstBreak == StringRef::npos
                                 ? LiteralText
                                 : LiteralText.substr(0, FirstBreak);
   CSharpStringLiteral->ColumnWidth = encoding::columnWidthWithTabs(
       FirstLineText, CSharpStringLiteral->OriginalColumn, Style.TabWidth,
       Encoding);
   size_t LastBreak = LiteralText.rfind('\n');
   if (LastBreak != StringRef::npos) {
     CSharpStringLiteral->IsMultiline = true;
-    unsigned StartColumn = 0; // The template tail spans the entire line.
+    unsigned StartColumn = 0;
     CSharpStringLiteral->LastLineColumnWidth = encoding::columnWidthWithTabs(
         LiteralText.substr(LastBreak + 1, LiteralText.size()), StartColumn,
         Style.TabWidth, Encoding);
   }
 
   SourceLocation loc = Offset < Lex->getBuffer().end()
                            ? Lex->getSourceLocation(Offset + 1)
                            : SourceMgr.getLocForEndOfFile(ID);

clang/lib/Format/TokenAnnotator.cpp

case tok::colon:
             (!Contexts.back().IsExpression &&
              Contexts.back().ContextKind == tok::l_brace) || // object type
             (Contexts.size() == 1 &&
              Line.MustBeDeclaration)) { // method/property declaration
           Contexts.back().IsExpression = false;
           Tok->Type = TT_JsTypeColon;
           break;
         }
+      } else if (Style.isCSharp()) {
+        if (Contexts.back().ContextKind == tok::l_paren) {
+          Tok->Type = TT_CSharpNamedArgumentColon;
+          break;
+        }
       }
       if (Contexts.back().ColonIsDictLiteral ||
           Style.Language == FormatStyle::LK_Proto ||
           Style.Language == FormatStyle::LK_TextProto) {
         Tok->Type = TT_DictLiteral;
         if (Style.Language == FormatStyle::LK_TextProto) {
           if (FormatToken *Previous = Tok->getPreviousNonComment())
             Previous->Type = TT_SelectorName;
if (Right.is(tok::colon)) {
     if (Left.is(tok::question))
       return false;
     if (Right.is(TT_InlineASMColon) && Left.is(tok::coloncolon))
       return false;
     if (Right.is(TT_DictLiteral))
       return Style.SpacesInContainerLiterals;
     if (Right.is(TT_AttributeColon))
       return false;
+    if (Right.is(TT_CSharpNamedArgumentColon))
+      return false;
     return true;
   }
   if (Left.is(TT_UnaryOperator)) {
     if (!Right.is(tok::l_paren)) {
       // The alternative operators for ~ and ! are "compl" and "not".
       // If they are used instead, we do not want to combine them with
       // the token to the right, unless that is a left paren.
       if (Left.is(tok::exclaim) && Left.TokenText == "not")

 }
 
 bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
                                      const FormatToken &Right) {
   const FormatToken &Left = *Right.Previous;
   if (Right.NewlinesBefore > 1 && Style.MaxEmptyLinesToKeep > 0)
     return true;
 
-  if (Style.Language == FormatStyle::LK_JavaScript) {
+  if (Style.isCSharp()) {
+    if (Right.is(TT_CSharpNamedArgumentColon) ||
+        Left.is(TT_CSharpNamedArgumentColon))
+      return false;
+  } else if (Style.Language == FormatStyle::LK_JavaScript) {
     // FIXME: This might apply to other languages and token kinds.
     if (Right.is(tok::string_literal) && Left.is(tok::plus) && Left.Previous &&
         Left.Previous->is(tok::string_literal))
       return true;
     if (Left.is(TT_DictLiteral) && Left.is(tok::l_brace) && Line.Level == 0 &&
         Left.Previous && Left.Previous->is(tok::equal) &&
         Line.First->isOneOf(tok::identifier, Keywords.kw_import, tok::kw_export,
                             tok::kw_const) &&
bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
   }
 
   return false;
 }
 
 bool TokenAnnotator::canBreakBefore(const AnnotatedLine &Line,
                                     const FormatToken &Right) {
   const FormatToken &Left = *Right.Previous;
-
+  if (Style.isCSharp()) {
+    if (Left.is(TT_CSharpNamedArgumentColon) ||
+        Right.is(TT_CSharpNamedArgumentColon))
+      return false;
+  }
   // Language-specific stuff.
   if (Style.Language == FormatStyle::LK_Java) {
     if (Left.isOneOf(Keywords.kw_throws, Keywords.kw_extends,
                      Keywords.kw_implements))
       return false;
     if (Right.isOneOf(Keywords.kw_throws, Keywords.kw_extends,
                       Keywords.kw_implements))
       return true;

clang/unittests/Format/FormatTestCSharp.cpp

PrintOrderDetails(orderNum: 31, productName: "Red Mug",
                   sellerName: "Gift Shop");)",
                Style);
 
   // Ensure that trailing comments do not cause problems.
   verifyFormat(R"(//
 PrintOrderDetails(orderNum: 31, productName: "Red Mug",  // comment
                   sellerName: "Gift Shop");)",
                Style);
+
+  verifyFormat(R"(foreach (var tickCount in task.Begin(seed: 0)) {)", Style);
 }
 
 TEST_F(FormatTestCSharp, CSharpPropertyAccessors) {
   FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
 
   verifyFormat("int Value { get }", Style);
   verifyFormat("int Value { get; }", Style);
   verifyFormat("int Value { internal get; }", Style);