Fix diff parser: Avoid indentation issues

parso/python/diff.py

@@ -564,6 +564,10 @@ class _NodesTree(object):
 
         Returns the number of tree nodes that were copied.
         """
+        if tree_nodes[0].type == 'error_leaf' and tree_nodes[0].token_type == 'INDENT':
+            # Avoid copying error indents. Just parse them again.
+            return []
+
         self._get_insertion_node(tree_nodes[0])
 
         new_nodes, self._working_stack = self._copy_nodes(

test/test_diff_parser.py

@@ -774,3 +774,47 @@ def test_parentheses_before_method(differ):
     differ.initialize(code1)
     differ.parse(code2, parsers=2, copies=1, expect_error_leaves=True)
     differ.parse(code1, parsers=1, copies=1)
+
+
+def test_indentation_issues(differ):
+    code1 = dedent('''\
+        class C:
+            def f():
+                1
+                if 2:
+                    return 3
+
+            def g():
+                to_be_removed
+                pass
+        ''')
+
+    code2 = dedent('''\
+        class C:
+            def f():
+                1
+        ``something``, very ``weird``).
+                if 2:
+                    return 3
+
+            def g():
+                to_be_removed
+                pass
+        ''')
+
+    code3 = dedent('''\
+        class C:
+            def f():
+                1
+                if 2:
+                    return 3
+
+            def g():
+                pass
+        ''')
+
+    differ.initialize(code1)
+    differ.parse(code2, parsers=1, copies=2, expect_error_leaves=True)
+    differ.parse(code1, parsers=2, copies=1)
+    differ.parse(code3, parsers=1, copies=1)
+    differ.parse(code1, parsers=1, copies=2)