Look for last newline to calculate prefix

Author: bwendling

yapf/yapflib/comment_splicer.py

@@ -62,7 +62,7 @@ def _VisitNodeRec(node):
           child_prefix = child.prefix.lstrip('\n')
           prefix_indent = child_prefix[:child_prefix.find('#')]
           if '\n' in prefix_indent:
-            prefix_indent = prefix_indent[prefix_indent.find('\n') + 1:]
+            prefix_indent = prefix_indent[prefix_indent.rfind('\n') + 1:]
           child.prefix = ''
 
           if child.type == token.NEWLINE:

yapftests/reformatter_facebook_test.py

@@ -375,21 +375,33 @@ def _pack_results_for_constraint_or(cls, combination, constraints):
     self.assertCodeEqual(code, reformatted_code)
 
   def testCommentWithNewlinesInPrefix(self):
-    code = textwrap.dedent("""\
+    unformatted_code = textwrap.dedent("""\
         def foo():
             if 0:
                 return False
                 
+                
             #a deadly comment
             elif 1:
                 return True
 
 
         print(foo())
         """)
-    uwlines = reformatter_test.ParseAndUnwrap(code)
-    reformatted_code = reformatter.Reformat(uwlines)
-    self.assertCodeEqual(code, reformatted_code)
+    expected_formatted_code = textwrap.dedent("""\
+        def foo():
+            if 0:
+                return False
+                
+            #a deadly comment
+            elif 1:
+                return True
+
+
+        print(foo())
+        """)
+    uwlines = reformatter_test.ParseAndUnwrap(unformatted_code)
+    self.assertCodeEqual(expected_formatted_code, reformatter.Reformat(uwlines))
 
 
 if __name__ == '__main__':