[clang-format] js handle anonymous classes (llvm#106242)

Addresses a regression in JavaScript when formatting anonymous classes.

---------

Co-authored-by: Owen Pan <owenpiano@gmail.com>

Author: krasimirgg

clang/lib/Format/UnwrappedLineParser.cpp

@@ -3992,6 +3992,9 @@ void UnwrappedLineParser::parseRecord(bool ParseAsExpr) {
   auto IsNonMacroIdentifier = [](const FormatToken *Tok) {
     return Tok->is(tok::identifier) && Tok->TokenText != Tok->TokenText.upper();
   };
+  // JavaScript/TypeScript supports anonymous classes like:
+  // a = class extends foo { }
+  bool JSPastExtendsOrImplements = false;
   // The actual identifier can be a nested name specifier, and in macros
   // it is often token-pasted.
   // An [[attribute]] can be before the identifier.
@@ -4002,6 +4005,7 @@ void UnwrappedLineParser::parseRecord(bool ParseAsExpr) {
           FormatTok->isOneOf(tok::period, tok::comma))) {
     if (Style.isJavaScript() &&
         FormatTok->isOneOf(Keywords.kw_extends, Keywords.kw_implements)) {
+      JSPastExtendsOrImplements = true;
       // JavaScript/TypeScript supports inline object types in
       // extends/implements positions:
       //     class Foo implements {bar: number} { }
@@ -4027,8 +4031,8 @@ void UnwrappedLineParser::parseRecord(bool ParseAsExpr) {
     case tok::coloncolon:
       break;
     default:
-      if (!ClassName && Previous->is(tok::identifier) &&
-          Previous->isNot(TT_AttributeMacro)) {
+      if (!JSPastExtendsOrImplements && !ClassName &&
+          Previous->is(tok::identifier) && Previous->isNot(TT_AttributeMacro)) {
         ClassName = Previous;
       }
     }

clang/unittests/Format/FormatTestJS.cpp

@@ -579,6 +579,14 @@ TEST_F(FormatTestJS, GoogScopes) {
                "});");
 }
 
+TEST_F(FormatTestJS, GoogAnonymousClass) {
+  verifyFormat("a = class extends goog.structs.a {\n"
+               "  a() {\n"
+               "    return 0;\n"
+               "  }\n"
+               "};");
+}
+
 TEST_F(FormatTestJS, IIFEs) {
   // Internal calling parens; no semi.
   verifyFormat("(function() {\n"

clang/unittests/Format/TokenAnnotatorTest.cpp

@@ -3238,6 +3238,12 @@ TEST_F(TokenAnnotatorTest, BraceKind) {
   EXPECT_BRACE_KIND(Tokens[8], BK_BracedInit);
   EXPECT_BRACE_KIND(Tokens[11], BK_BracedInit);
   EXPECT_BRACE_KIND(Tokens[13], BK_Block);
+
+  Tokens = annotate("a = class extends goog.a {};",
+                    getGoogleStyle(FormatStyle::LK_JavaScript));
+  ASSERT_EQ(Tokens.size(), 11u) << Tokens;
+  EXPECT_TOKEN(Tokens[7], tok::l_brace, TT_ClassLBrace);
+  EXPECT_BRACE_KIND(Tokens[7], BK_Block);
 }
 
 TEST_F(TokenAnnotatorTest, UnderstandsElaboratedTypeSpecifier) {