[clang-format] do not break before { in JS comments

[krasimir]

Summary

In JavaScript some @tags can be followed by {, and machinery that parses
these comments will fail to understand the comment if followed by a line break.

clang-format already handles this case by not breaking before { in comments.
However this was not working in cases when the column limit falls within @tag
or between @tag and {. This adapts clang-format for this case.

[krasimir]

update test case range

[krasimir]

collect commits

clang/lib/Format/BreakableToken.cpp

for (unsigned NumChars = 0;
     unsigned BytesInChar =
         encoding::getCodePointNumBytes(Text[MaxSplitBytes], Encoding);
     NumChars +=
         encoding::columnWidthWithTabs(Text.substr(MaxSplitBytes, BytesInChar),
                                       ContentStartColumn, TabWidth, Encoding);
     MaxSplitBytes += BytesInChar;
   }
 
+  // In JavaScript, some @tags can be followed by {, and machinery that parses
+  // these comments will fail to understand the comment if followed by a line
+  // break. So avoid ever breaking before a {.
+  if (Style.Language == FormatStyle::LK_JavaScript) {
+    StringRef::size_type SpaceOffset =
+        Text.find_first_of(Blanks, MaxSplitBytes);
+    if (SpaceOffset != StringRef::npos && SpaceOffset + 1 < Text.size() &&
+        Text[SpaceOffset + 1] == '{') {
+      MaxSplitBytes = SpaceOffset + 1;
+    }
+  }
+
   StringRef::size_type SpaceOffset = Text.find_last_of(Blanks, MaxSplitBytes);
 
   static const auto kNumberedListRegexp = llvm::Regex("^[1-9][0-9]?\\.");
   while (SpaceOffset != StringRef::npos) {
     // Do not split before a number followed by a dot: this would be interpreted
     // as a numbered list, which would prevent re-flowing in subsequent passes.
     if (kNumberedListRegexp.match(Text.substr(SpaceOffset).ltrim(Blanks)))
       SpaceOffset = Text.find_last_of(Blanks, SpaceOffset);
-    // In JavaScript, some @tags can be followed by {, and machinery that parses
-    // these comments will fail to understand the comment if followed by a line
-    // break. So avoid ever breaking before a {.
+    // Avoid ever breaking before a { in JavaScript.
     else if (Style.Language == FormatStyle::LK_JavaScript &&
              SpaceOffset + 1 < Text.size() && Text[SpaceOffset + 1] == '{')
       SpaceOffset = Text.find_last_of(Blanks, SpaceOffset);
     else
       break;
   }
 
   if (SpaceOffset == StringRef::npos ||

clang/unittests/Format/FormatTestJS.cpp

TEST_F(FormatTestJS, JSDocAnnotations) {
   // make sure clang-format doesn't break before *any* '{'
   verifyFormat("/**\n"
                " * @lala {lala {lalala\n"
                " */\n",
                "/**\n"
                " * @lala {lala {lalala\n"
                " */\n",
                getGoogleJSStyleWithColumns(20));
+  // cases where '{' is around the column limit
+  for (int ColumnLimit = 6; ColumnLimit < 13; ++ColumnLimit) {
+    verifyFormat("/**\n"
+                 " * @param {type}\n"
+                 " */",
+                 "/**\n"
+                 " * @param {type}\n"
+                 " */",
+                 getGoogleJSStyleWithColumns(ColumnLimit));
+  }
   verifyFormat("/**\n"
                " * @see http://very/very/long/url/is/long\n"
                " */",
                "/**\n"
                " * @see http://very/very/long/url/is/long\n"
                " */",
                getGoogleJSStyleWithColumns(20));
   verifyFormat("/**\n"