Fix a bug that might have caused an endless while loop a while ago. Fixes #878.

jedi/parser/diff.py

@@ -148,6 +148,7 @@ class DiffParser(object):
             # everything else we keep working with lines_new here.
             self._parser_lines_new = list(lines_new)
             self._parser_lines_new[-1] += '\n'
+            self._parser_lines_new.append('')
             self._added_newline = True
 
         self._reset()
@@ -428,10 +429,8 @@ class _NodesStackNode(object):
         self.children_groups.append(group)
 
     def get_last_line(self, suffix):
-        if not self.children_groups:
-            assert not self.parent
-            return 0
-
+        line = 0
+        if self.children_groups:
             last_leaf = self.children_groups[-1].children[-1].get_last_leaf()
             line = last_leaf.end_pos[0]
 
@@ -460,7 +459,7 @@ class _NodesStack(object):
         return not self._base_node.children
 
     @property
-    def parsed_until_line(self, ):
+    def parsed_until_line(self):
         return self._tos.get_last_line(self.prefix)
 
     def _get_insertion_node(self, indentation_node):

test/test_parser/test_diff_parser.py

@@ -423,6 +423,21 @@ def test_whitespace_at_end(differ):
     differ.parse(code + '\n', parsers=1, copies=1)
 
 
+def test_endless_while_loop(differ):
+    """
+    This was a bug in Jedi #878.
+    """
+    code = '#dead'
+    differ.initialize(code)
+    module = differ.parse(code, parsers=1)
+    assert module.end_pos == (1, 5)
+
+    code = '#dead\n'
+    differ.initialize(code)
+    module = differ.parse(code + '\n', parsers=1)
+    assert module.end_pos == (3, 0)
+
+
 def test_in_class_movements(differ):
     code1 = dedent("""\
         class PlaybookExecutor: