Auto merge of #10786 - zwn:tidy-modelines, r=Manishearth

tidy check for vim and emacs modelines

See #10719.

It skips *.webidl files for now since I am not sure where they come from and if they should be edited in tree or not.

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python/tidy/servo_tidy_tests/modeline.txt

@@ -0,0 +1,5 @@
+# vim: set noexpandtab:
+// vi: et:
+/* ex: et:
+anything -*-Lisp-*-
+ -*- mode: Lisp -*-

python/tidy/servo_tidy_tests/test_tidy.py

@@ -89,6 +89,14 @@ class CheckTidiness(unittest.TestCase):
         self.assertEqual('found asterisk instead of minimum version number', errors.next()[2])
         self.assertNoMoreErrors(errors)
 
+    def test_modeline(self):
+        errors = tidy.collect_errors_for_files(iterFile('modeline.txt'), [], [tidy.check_modeline])
+        self.assertEqual('vi modeline present', errors.next()[2])
+        self.assertEqual('vi modeline present', errors.next()[2])
+        self.assertEqual('vi modeline present', errors.next()[2])
+        self.assertEqual('emacs file variables present', errors.next()[2])
+        self.assertEqual('emacs file variables present', errors.next()[2])
+
 
 def do_tests():
     suite = unittest.TestLoader().loadTestsFromTestCase(CheckTidiness)