[javascript mode] Handle trailing commas better

Author: marijnh

mode/javascript/javascript.js

@@ -495,7 +495,10 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
       if (type == ",") {
         var lex = cx.state.lexical;
         if (lex.info == "call") lex.pos = (lex.pos || 0) + 1;
-        return cont(what, proceed);
+        return cont(function(type, value) {
+          if (type == end || value == end) return pass()
+          return pass(what)
+        }, proceed);
       }
       if (type == end || value == end) return cont();
       return cont(expect(end));

mode/javascript/test.js

@@ -44,6 +44,9 @@
      "  [keyword import] { [def encrypt], [def decrypt] } [keyword from] [string 'crypto'];",
      "}");
 
+  MT("import_trailing_comma",
+     "[keyword import] {[def foo], [def bar],} [keyword from] [string 'baz']")
+
   MT("const",
      "[keyword function] [def f]() {",
      "  [keyword const] [[ [def a], [def b] ]] [operator =] [[ [number 1], [number 2] ]];",