[clang-format] don't break between function and function name in JS

[krasimir]

Summary

The patch https://reviews.llvm.org/D105964 (https://github.com/llvm/llvm-project/commit/58494c856a15f5b0e886c7baf5d505ac6c05dfe5)
updated detection of function declaration names. It had the unfortunate
consequence that it started breaking between function and the function
name in some cases in JavaScript code.

This patch addresses this.

[MyDeveloperDay]

LGTM

[owenpan]

Thanks!

clang/lib/Format/ContinuationIndenter.cpp

if (Previous.is(TT_LeadingJavaAnnotation) && Current.isNot(tok::l_paren) &&
         Current.isNot(TT_LeadingJavaAnnotation))
       return true;
   }
 
   // If the return type spans multiple lines, wrap before the function name.
   if (((Current.is(TT_FunctionDeclarationName) &&
         // Don't break before a C# function when no break after return type
         (!Style.isCSharp() ||
-         Style.AlwaysBreakAfterReturnType != FormatStyle::RTBS_None)) ||
+         Style.AlwaysBreakAfterReturnType != FormatStyle::RTBS_None) &&
+        // Don't always break between a JavaScript `function` and the function
+        // name.
+        Style.Language != FormatStyle::LK_JavaScript) ||
        (Current.is(tok::kw_operator) && !Previous.is(tok::coloncolon))) &&
       !Previous.is(tok::kw_template) && State.Stack.back().BreakBeforeParameter)
     return true;
 
   // The following could be precomputed as they do not depend on the state.
   // However, as they should take effect only if the UnwrappedLine does not fit
   // into the ColumnLimit, they are checked here in the ContinuationIndenter.
   if (Style.ColumnLimit != 0 && Previous.is(BK_Block) &&

clang/unittests/Format/FormatTestJS.cpp

verifyFormat("function aFunction() {}\n"
                "(function f() {\n"
                "  var x = 1;\n"
                "}());\n");
   verifyFormat("function aFunction() {}\n"
                "{\n"
                "  let x = 1;\n"
                "  console.log(x);\n"
                "}\n");
+  EXPECT_EQ("a = function(x) {}\n"
+            "\n"
+            "function f(x) {}",
+            format("a = function(x) {}\n"
+                   "\n"
+                   "function f(x) {}",
+                   getGoogleJSStyleWithColumns(20)));
 }
 
 TEST_F(FormatTestJS, GeneratorFunctions) {
   verifyFormat("function* f() {\n"
                "  let x = 1;\n"
                "  yield x;\n"
                "  yield* something();\n"
                "  yield [1, 2];\n"