clang-format: [JS] Don't indent JavaScript IIFEs.

Because IIFEs[1] are often used like an anonymous namespace around large
sections of JavaScript code, it's useful not to indent to them (which
effectively reduces the column limit by the indent amount needlessly).

It's also common for developers to wrap these around entire files or
libraries. When adopting clang-format, changing the indent entire file
can reduce the usefulness of the blame annotations.

Patch by danbeam, thanks!

Differential Revision: https://reviews.llvm.org/D32989

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@302580 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Format/UnwrappedLineParser.cpp

@@ -476,6 +476,24 @@ static bool isGoogScope(const UnwrappedLine &Line) {
   return I->Tok->is(tok::l_paren);
 }
 
+static bool isIIFE(const UnwrappedLine &Line,
+                   const AdditionalKeywords &Keywords) {
+  // Look for the start of an immediately invoked anonymous function.
+  // https://en.wikipedia.org/wiki/Immediately-invoked_function_expression
+  // This is commonly done in JavaScript to create a new, anonymous scope.
+  // Example: (function() { ... })()
+  if (Line.Tokens.size() < 3)
+    return false;
+  auto I = Line.Tokens.begin();
+  if (I->Tok->isNot(tok::l_paren))
+    return false;
+  ++I;
+  if (I->Tok->isNot(Keywords.kw_function))
+    return false;
+  ++I;
+  return I->Tok->is(tok::l_paren);
+}
+
 static bool ShouldBreakBeforeBrace(const FormatStyle &Style,
                                    const FormatToken &InitialToken) {
   if (InitialToken.is(tok::kw_namespace))
@@ -493,15 +511,16 @@ void UnwrappedLineParser::parseChildBlock() {
   FormatTok->BlockKind = BK_Block;
   nextToken();
   {
-    bool GoogScope =
-        Style.Language == FormatStyle::LK_JavaScript && isGoogScope(*Line);
+    bool SkipIndent =
+        (Style.Language == FormatStyle::LK_JavaScript &&
+         (isGoogScope(*Line) || isIIFE(*Line, Keywords)));
     ScopedLineState LineState(*this);
     ScopedDeclarationState DeclarationState(*Line, DeclarationScopeStack,
                                             /*MustBeDeclaration=*/false);
-    Line->Level += GoogScope ? 0 : 1;
+    Line->Level += SkipIndent ? 0 : 1;
     parseLevel(/*HasOpeningBrace=*/true);
     flushComments(isOnNewLine(*FormatTok));
-    Line->Level -= GoogScope ? 0 : 1;
+    Line->Level -= SkipIndent ? 0 : 1;
   }
   nextToken();
 }

unittests/Format/FormatTestJS.cpp

@@ -367,6 +367,25 @@ TEST_F(FormatTestJS, GoogScopes) {
                "});");
 }
 
+TEST_F(FormatTestJS, IIFEs) {
+  // Internal calling parens; no semi.
+  verifyFormat("(function() {\n"
+               "var a = 1;\n"
+               "}())");
+  // External calling parens; no semi.
+  verifyFormat("(function() {\n"
+               "var b = 2;\n"
+               "})()");
+  // Internal calling parens; with semi.
+  verifyFormat("(function() {\n"
+               "var c = 3;\n"
+               "}());");
+  // External calling parens; with semi.
+  verifyFormat("(function() {\n"
+               "var d = 4;\n"
+               "})();");
+}
+
 TEST_F(FormatTestJS, GoogModules) {
   verifyFormat("goog.module('this.is.really.absurdly.long');",
                getGoogleJSStyleWithColumns(40));