clang-format: [JS] Conservatively introduce column layout for JS array

initializers. For now, only use it for 20 items or more. Otherwise,
clang-format formats these one-per-line and thus increases the vertical
code size a lot.

llvm-svn: 256246

clang/lib/Format/FormatToken.cpp

@@ -80,8 +80,8 @@ unsigned CommaSeparatedList::formatAfterToken(LineState &State,
   // Ensure that we start on the opening brace.
   const FormatToken *LBrace =
       State.NextToken->Previous->getPreviousNonComment();
-  if (!LBrace || LBrace->isNot(tok::l_brace) || LBrace->BlockKind == BK_Block ||
+  if (!LBrace || !LBrace->isOneOf(tok::l_brace, TT_ArrayInitializerLSquare) ||
-      LBrace->Type == TT_DictLiteral ||
+      LBrace->BlockKind == BK_Block || LBrace->Type == TT_DictLiteral ||
       LBrace->Next->Type == TT_DesignatedInitializerPeriod)
     return 0;
 
@@ -144,7 +144,8 @@ static unsigned CodePointsBetween(const FormatToken *Begin,
 
 void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
   // FIXME: At some point we might want to do this for other lists, too.
-  if (!Token->MatchingParen || Token->isNot(tok::l_brace))
+  if (!Token->MatchingParen ||
+      !Token->isOneOf(tok::l_brace, TT_ArrayInitializerLSquare))
     return;
 
   // In C++11 braced list style, we should not format in columns unless they
@@ -154,6 +155,12 @@ void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
       Commas.size() < 19)
     return;
 
+  // Limit column layout for JavaScript array initializers to 20 or more items
+  // for now to introduce it carefully. We can become more aggressive if this
+  // necessary.
+  if (Token->is(TT_ArrayInitializerLSquare) && Commas.size() < 19)
+    return;
+
   // Column format doesn't really make sense if we don't align after brackets.
   if (Style.AlignAfterOpenBracket == FormatStyle::BAS_DontAlign)
     return;
@@ -213,7 +220,8 @@ void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
 
   // Don't use column layout for nested lists, lists with few elements and in
   // presence of separating comments.
-  if (Token->NestingLevel != 0 || Commas.size() < 5 || HasSeparatingComment)
+  if ((Token->NestingLevel != 0 && Token->is(tok::l_brace)) ||
+      Commas.size() < 5 || HasSeparatingComment)
     return;
 
   // We can never place more than ColumnLimit / 3 items in a row (because of the

clang/unittests/Format/FormatTestJS.cpp

@@ -314,6 +314,17 @@ TEST_F(FormatTestJS, ArrayLiterals) {
   verifyFormat("someFunction([], {a: a});");
 }
 
+TEST_F(FormatTestJS, ColumnLayoutForArrayLiterals) {
+  verifyFormat("var array = [\n"
+               "  a, a, a, a, a, a, a, a, a, a, a, a, a, a, a,\n"
+               "  a, a, a, a, a, a, a, a, a, a, a, a, a, a, a,\n"
+               "];");
+  verifyFormat("var array = someFunction([\n"
+               "  a, a, a, a, a, a, a, a, a, a, a, a, a, a, a,\n"
+               "  a, a, a, a, a, a, a, a, a, a, a, a, a, a, a,\n"
+               "]);");
+}
+
 TEST_F(FormatTestJS, FunctionLiterals) {
   verifyFormat("doFoo(function() {});");
   verifyFormat("doFoo(function() { return 1; });");