Merge pull request #445 from hhatto/fix-w503

Fix w503

Author: hhatto

autopep8.py

@@ -1217,16 +1217,24 @@ def fix_w503(self, result):
             return
         # find comment
         comment_index = 0
+        found_not_comment_only_line = False
         comment_only_linenum = 0
         for i in range(5):
             # NOTE: try to parse code in 5 times
             if (line_index - i) < 0:
                 break
             from_index = line_index - i - 1
+            if from_index < 0 or len(self.source) <= from_index:
+                break
             to_index = line_index + 1
-            if self.source[from_index].lstrip()[0] == '#':
+            strip_line = self.source[from_index].lstrip()
+            if (
+                not found_not_comment_only_line and
+                strip_line and strip_line[0] == '#'
+            ):
                 comment_only_linenum += 1
                 continue
+            found_not_comment_only_line = True
             try:
                 ts = generate_tokens("".join(self.source[from_index:to_index]))
             except (SyntaxError, tokenize.TokenError):

test/test_autopep8.py

@@ -4352,6 +4352,26 @@ def test_w503_with_line_comment(self):
         with autopep8_context(line, options=['--select=W503', '--ignore=E']) as result:
             self.assertEqual(fixed, result)
 
+    def test_w503_with_empty_line(self):
+        line = """\
+
+# this is comment
+a = 2
+b = (1 +
+     2 +
+     3) / 2.0
+"""
+        fixed = """\
+
+# this is comment
+a = 2
+b = (1 +
+     2 +
+     3) / 2.0
+"""
+        with autopep8_context(line, options=['--ignore=E721']) as result:
+            self.assertEqual(fixed, result)
+
     def test_w503_with_line_comments(self):
         line = '(width == 0\n # this is comment\n # comment2\n + height == 0)\n'
         fixed = '(width == 0 +\n # this is comment\n # comment2\n height == 0)\n'