[javascript mode] Improve indentation of hanging else clauses

Closes #2429

Author: marijnh

mode/javascript/javascript.js

@@ -314,7 +314,11 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
     if (type == "keyword b") return cont(pushlex("form"), statement, poplex);
     if (type == "{") return cont(pushlex("}"), block, poplex);
     if (type == ";") return cont();
-    if (type == "if") return cont(pushlex("form"), expression, statement, poplex, maybeelse);
+    if (type == "if") {
+      if (cx.state.lexical.info == "else" && cx.state.cc[cx.state.cc.length - 1] == poplex)
+        cx.state.cc.pop()();
+      return cont(pushlex("form"), expression, statement, poplex, maybeelse);
+    }
     if (type == "function") return cont(functiondef);
     if (type == "for") return cont(pushlex("form"), forspec, statement, poplex);
     if (type == "variable") return cont(pushlex("stat"), maybelabel);
@@ -482,7 +486,7 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
     if (type == ",") return cont(vardef);
   }
   function maybeelse(type, value) {
-    if (type == "keyword b" && value == "else") return cont(pushlex("form"), statement, poplex);
+    if (type == "keyword b" && value == "else") return cont(pushlex("form", "else"), statement, poplex);
   }
   function forspec(type) {
     if (type == "(") return cont(pushlex(")"), forspec1, expect(")"), poplex);
@@ -595,7 +599,7 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
       if (state.tokenize != tokenBase) return 0;
       var firstChar = textAfter && textAfter.charAt(0), lexical = state.lexical;
       // Kludge to prevent 'maybelse' from blocking lexical scope pops
-      for (var i = state.cc.length - 1; i >= 0; --i) {
+      if (!/^\s*else\b/.test(textAfter)) for (var i = state.cc.length - 1; i >= 0; --i) {
         var c = state.cc[i];
         if (c == poplex) lexical = lexical.prev;
         else if (c != maybeelse) break;

mode/javascript/test.js

@@ -104,6 +104,22 @@
      "  [keyword debugger];",
      "}");
 
+  MT("indent_else",
+     "[keyword for] (;;)",
+     "  [keyword if] ([variable foo])",
+     "    [keyword if] ([variable bar])",
+     "      [number 1];",
+     "    [keyword else]",
+     "      [number 2];",
+     "  [keyword else]",
+     "    [number 3];");
+
+  MT("indent_below_if",
+     "[keyword for] (;;)",
+     "  [keyword if] ([variable foo])",
+     "    [number 1];",
+     "[number 2];");
+
   MT("multilinestring",
      "[keyword var] [variable x] [operator =] [string 'foo\\]",
      "[string bar'];");