clang-format: [js] support AtScript style annotations for JS.

[mprobst]

Summary

Based on Java annotation support and style.

[djasper]

Submitted as r229703.

lib/Format/TokenAnnotator.cpp

if (Current.is(Keywords.kw_instanceof)) {
       }
     } else if (Current.isOneOf(tok::identifier, tok::kw_const) &&
                Current.Previous &&
                !Current.Previous->isOneOf(tok::equal, tok::at) &&
                Line.MightBeFunctionDecl && Contexts.size() == 1) {
       // Line.MightBeFunctionDecl can only be true after the parentheses of a
       // function declaration have been found.
       Current.Type = TT_TrailingAnnotation;
-    } else if (Style.Language == FormatStyle::LK_Java && Current.Previous) {
+    } else if ((Style.Language == FormatStyle::LK_Java ||
+                Style.Language == FormatStyle::LK_JavaScript) &&
+               Current.Previous) {
       if (Current.Previous->is(tok::at) &&
           Current.isNot(Keywords.kw_interface)) {
         const FormatToken &AtToken = *Current.Previous;
         const FormatToken *Previous = AtToken.getPreviousNonComment();
         if (!Previous || Previous->is(TT_LeadingJavaAnnotation))
           Current.Type = TT_LeadingJavaAnnotation;
         else
           Current.Type = TT_JavaAnnotation;
bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
   if (Style.Language == FormatStyle::LK_JavaScript) {
     // FIXME: This might apply to other languages and token kinds.
     if (Right.is(tok::char_constant) && Left.is(tok::plus) && Left.Previous &&
         Left.Previous->is(tok::char_constant))
       return true;
     if (Left.is(TT_DictLiteral) && Left.is(tok::l_brace) &&
         Left.NestingLevel == 0)
       return true;
+    if (Left.is(TT_LeadingJavaAnnotation) &&
+        Right.isNot(TT_LeadingJavaAnnotation) && Right.isNot(tok::l_paren) &&
+        Line.Last->is(tok::l_brace))
+      return true;
   } else if (Style.Language == FormatStyle::LK_Java) {
     if (Left.is(TT_LeadingJavaAnnotation) &&
         Right.isNot(TT_LeadingJavaAnnotation) && Right.isNot(tok::l_paren) &&
         Line.Last->is(tok::l_brace))
       return true;
     if (Right.is(tok::plus) && Left.is(tok::string_literal) && Right.Next &&
         Right.Next->is(tok::string_literal))
       return true;

unittests/Format/FormatTestJS.cpp

TEST_F(FormatTestJS, ClassDeclarations) {
   verifyFormat("class C {\n  x(): string => 12;\n}");
   verifyFormat("class C {\n  ['x' + 2]: string = 12;\n}");
   verifyFormat("class C {\n  private x: string = 12;\n}");
   verifyFormat("class C {\n  private static x: string = 12;\n}");
   verifyFormat("class C {\n  static x(): string { return 'asd'; }\n}");
   verifyFormat("class C extends P implements I {}");
 }
 
+TEST_F(FormatTestJS, MetadataAnnotations) {
+  verifyFormat("@A\nclass C {\n}");
+  verifyFormat("@A({arg: 'value'})\nclass C {\n}");
+  verifyFormat("@A\n@B\nclass C {\n}");
+  verifyFormat("class C {\n  @A x: string;\n}");
+  verifyFormat("class C {\n  @A\n  private x(): string {\n    return 'y';\n  }\n}");
+}
+
 } // end namespace tooling
 } // end namespace clang