From 2dbcbd357d1da1adf9c512d150e68424faa46d75 Mon Sep 17 00:00:00 2001
From: Krasimir Georgiev <krasimir@google.com>
Date: Fri, 6 Nov 2020 10:33:23 +0100
Subject: [PATCH] [clang-format] do not break before { in JS comments

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.

Reviewed By: mprobst

Differential Revision: https://reviews.llvm.org/D90908
---
 clang/lib/Format/BreakableToken.cpp     | 16 +++++++++++++---
 clang/unittests/Format/FormatTestJS.cpp | 10 ++++++++++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Format/BreakableToken.cpp b/clang/lib/Format/BreakableToken.cpp
index 15fbe3b..2ef1540 100644
--- a/clang/lib/Format/BreakableToken.cpp
+++ b/clang/lib/Format/BreakableToken.cpp
@@ -86,6 +86,18 @@ getCommentSplit(StringRef Text, unsigned ContentStartColumn,
     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]?\\.");
@@ -94,9 +106,7 @@ getCommentSplit(StringRef Text, unsigned ContentStartColumn,
     // 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);
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index da26a9b..d140fe5 100644
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -2184,6 +2184,16 @@ TEST_F(FormatTestJS, JSDocAnnotations) {
                " * @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"
                " */",
-- 
2.7.4