Pop grammar rules that result in infinite loops

spec/app/text-mate-grammar-spec.coffee

@@ -258,3 +258,13 @@ describe "TextMateGrammar", ->
         {tokens, ruleStack} = grammar.tokenizeLine("if(1){if(1){m()}}")
         expect(tokens[5]).toEqual value: "if", scopes: ["source.c", "meta.block.c", "keyword.control.c"]
         expect(tokens[10]).toEqual value: "m", scopes: ["source.c", "meta.block.c", "meta.block.c", "meta.function-call.c", "support.function.any-method.c"]
+
+    describe "when the grammar can infinitely loop over a line", ->
+      it "aborts tokenization", ->
+        spyOn(console, 'error')
+        window.loadPackage("package-with-infinite-loop-grammar")
+        grammar = syntax.grammarForFilePath("something.package-with-infinite-loop-grammar")
+        {tokens} = grammar.tokenizeLine("abc")
+        expect(tokens[0].value).toBe "a"
+        expect(tokens[1].value).toBe "bc"
+        expect(console.error).toHaveBeenCalled()

spec/fixtures/packages/package-with-infinite-loop-grammar/grammars/grammar.cson

@@ -0,0 +1,18 @@
+'fileTypes': ['package-with-infinite-loop-grammar']
+'name': 'package-with-infinite-loop-grammar'
+'scopeName': 'source.package-with-infinite-loop-grammar'
+
+# This grammar should loop forever if the line contains an `a`
+'patterns': [
+  {
+    'name': 'start'
+    'begin': '^'
+    'end': '$'
+    'patterns': [
+      {
+        name: 'negative-look-ahead'
+        match: "(?!a)"
+      }
+    ]
+  }
+]

src/app/text-mate-grammar.coffee

@@ -31,9 +31,10 @@ class TextMateGrammar
     ruleStack = new Array(ruleStack...) # clone ruleStack
     tokens = []
     position = 0
-
     loop
       scopes = scopesFromStack(ruleStack)
+      previousRuleStackLength = ruleStack.length
+      previousPosition = position
 
       if line.length == 0
         tokens = [new Token(value: "", scopes: scopes)]
@@ -61,6 +62,10 @@ class TextMateGrammar
           ))
         break
 
+      if position == previousPosition and ruleStack.length == previousRuleStackLength
+        console.error("Popping rule because it loops at column #{position} of line '#{line}'", _.clone(ruleStack))
+        ruleStack.pop()
+
     ruleStack.forEach (rule) -> rule.clearAnchorPosition()
     { tokens, ruleStack }