clang-format: [JS] Fix calculation of template string width.

[mprobst]

Summary

OriginalColumn might not be set, so fall back to Location and SourceMgr in case
it is missing. Also initialize end column in case the token is multi line, but
it's the ` token itself that starts the multi line.

[djasper]

Submitted as r236383, thank you!

lib/Format/Format.cpp

bool tryMergeJSRegexLiteral() {
     return false;
   }
 
   bool tryMergeTemplateString() {
     if (Tokens.size() < 2)
       return false;
 
     FormatToken *EndBacktick = Tokens.back();
-    // Backticks get lexed as tok:unknown tokens. If a template string contains
+    // 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::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 = 0;
+    unsigned EndColumnInFirstLine =
+        EndBacktick->OriginalColumn + EndBacktick->ColumnWidth;
     for (auto I = Tokens.rbegin() + 1, E = Tokens.rend(); I != E; I++) {
       ++TokenCount;
       if (I[0]->NewlinesBefore > 0 || 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))
for (auto I = Tokens.rbegin() + 1, E = Tokens.rend(); I != E; I++) {
         // 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;
-        Tokens.back()->LastLineColumnWidth = EndBacktick->OriginalColumn;
+        Tokens.back()->LastLineColumnWidth = EndOriginalColumn;
         Tokens.back()->IsMultiline = true;
       } else {
         // Token simply spans from start to end, +1 for the ` itself.
         Tokens.back()->ColumnWidth =
-            EndBacktick->OriginalColumn - Tokens.back()->OriginalColumn + 1;
+            EndOriginalColumn - Tokens.back()->OriginalColumn + 1;
       }
       return true;
     }
     return false;
   }
 
   bool tryMerge_TMacro() {
     if (Tokens.size() < 4)

unittests/Format/FormatTestJS.cpp

EXPECT_EQ("var x = `hello\n"
                    "  ${world}` >= some();",
                    getGoogleJSStyleWithColumns(22))); // Barely fits.
 
   verifyFormat("var x =\n    `h`;", getGoogleJSStyleWithColumns(13 - 1));
   EXPECT_EQ(
       "var x =\n    `multi\n  line`;",
       format("var x = `multi\n  line`;", getGoogleJSStyleWithColumns(14 - 1)));
 
+  // Make sure template strings get a proper ColumnWidth assigned, even if they
+  // are first token in line.
+  verifyFormat(
+      "var a = aaaaaaaaaaaaaaaaaaaaaaaaaaaa ||\n"
+      "        `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`;");
+
   // Two template strings.
   verifyFormat("var x = `hello` == `hello`;");
 
   // Comments in template strings.
   EXPECT_EQ("var x = `//a`;\n"
             "var y;",
             format("var x =\n `//a`;\n"
                    "var y  ;"));