Fix diff parser: If funcs are not copied, errors shouldn't either

parso/python/diff.py

@@ -638,21 +638,23 @@ class _NodesTree(object):
                 working_stack = new_working_stack
                 had_valid_suite_last = True
 
-        elif (last_node.type in ('error_leaf', 'error_node') or
+        if new_nodes:
-              _is_flow_node(new_nodes[-1])):
+            last_node = new_nodes[-1]
-            # Error leafs/nodes don't have a defined start/end. Error
+            if (last_node.type in ('error_leaf', 'error_node') or
-            # nodes might not end with a newline (e.g. if there's an
+                    _is_flow_node(new_nodes[-1])):
-            # open `(`). Therefore ignore all of them unless they are
+                # Error leafs/nodes don't have a defined start/end. Error
-            # succeeded with valid parser state.
+                # nodes might not end with a newline (e.g. if there's an
-            # If we copy flows at the end, they might be continued
+                # open `(`). Therefore ignore all of them unless they are
-            # after the copy limit (in the new parser).
+                # succeeded with valid parser state.
-            # In this while loop we try to remove until we find a newline.
+                # If we copy flows at the end, they might be continued
-            new_nodes.pop()
+                # after the copy limit (in the new parser).
-            while new_nodes:
+                # In this while loop we try to remove until we find a newline.
-                last_node = new_nodes[-1]
-                if last_node.get_last_leaf().type == 'newline':
-                    break
                 new_nodes.pop()
+                while new_nodes:
+                    last_node = new_nodes[-1]
+                    if last_node.get_last_leaf().type == 'newline':
+                        break
+                    new_nodes.pop()
 
         if new_nodes:
             if had_valid_suite_last:

test/test_diff_parser.py

@@ -852,3 +852,35 @@ def test_error_dedent_issues(differ):
     differ.initialize(code1)
     differ.parse(code2, parsers=5, copies=1, expect_error_leaves=True)
     differ.parse(code1, parsers=1, copies=0)
+
+
+def test_random_text_insertion(differ):
+    code1 = dedent('''\
+class C:
+    def f():
+        return node
+
+    def g():
+        try:
+            1
+        except KeyError:
+            2
+        ''')
+
+    code2 = dedent('''\
+class C:
+    def f():
+        return node
+Some'random text: yeah
+        for push in plan.dfa_pushes:
+
+    def g():
+        try:
+            1
+        except KeyError:
+            2
+        ''')
+
+    differ.initialize(code1)
+    differ.parse(code2, parsers=1, copies=1, expect_error_leaves=True)
+    differ.parse(code1, parsers=1, copies=1)