YapfBear: Catch parse errors and give result

The YapfBear earlier raised an error when the file was not parseable.
Now, that error is caught and a Result is given out mentioning that the
file has syntax errors and cannot be parsed.

Fixes #750

Author: AbdealiLoKo

bears/python/YapfBear.py

@@ -122,11 +122,22 @@ def run(self, filename, file,
         options += 'use_tabs = ' + str(not use_spaces)
         options = options.format(**locals())
 
-        with prepare_file(options.splitlines(keepends=True),
-                          None) as (file_, fname):
-            corrected = FormatFile(filename,
-                                   style_config=fname,
-                                   verify=False)[0].splitlines(True)
+        try:
+            with prepare_file(options.splitlines(keepends=True),
+                              None) as (file_, fname):
+                corrected = FormatFile(filename,
+                                       style_config=fname,
+                                       verify=False)[0].splitlines(True)
+        except SyntaxError as err:
+            if isinstance(err, IndentationError):
+                error_type = "indentation errors (" + err.args[0] + ')'
+            else:
+                error_type = "syntax errors"
+            yield Result.from_values(
+                self,
+                "The code cannot be parsed due to {0}.".format(error_type),
+                filename, line=err.lineno, column=err.offset)
+            return
         diffs = Diff.from_string_arrays(file, corrected).split_diff()
         for diff in diffs:
             yield Result(self,

tests/python/YapfBearTest.py

@@ -31,6 +31,23 @@ def test_eof_handling(self):
         self.check_validity(self.uut, ['a = 2'], valid=True)
         self.check_validity(self.uut, ['\n'], valid=True)
 
+    def test_invalid_python(self):
+        results = self.check_validity(
+            self.uut, ['def a():', ' b=1', '  bad indent'], valid=False)
+        self.assertEqual(len(results), 1, str(results))
+        self.assertIn('unexpected indent', results[0].message)
+
+        results = self.check_validity(
+            self.uut, ['def a():', '    b=1', '\ttab error'], valid=False)
+        self.assertEqual(len(results), 1, str(results))
+        self.assertIn('inconsistent use of tabs and spaces in indentation',
+                      results[0].message)
+
+        results = self.check_validity(
+            self.uut, ['def a(:', '    b=1', '\ttab error'], valid=False)
+        self.assertEqual(len(results), 1, str(results))
+        self.assertIn('syntax errors', results[0].message)
+
     def test_valid_python_2(self):
         self.check_validity(self.uut, ['print 1\n'], valid=True)