From 51a044cc702d842c28748fb448d063511cfc1ab0 Mon Sep 17 00:00:00 2001
From: Dave Halter <davidhalter88@gmail.com>
Date: Sun, 22 Mar 2020 12:37:01 +0100
Subject: [PATCH] Fix diff parser: Invalid dedents meant that sometimes the
 wrong parents were chosen, fixes davidhalter/jedi#1499

---
 parso/python/diff.py     | 11 ++++++++++-
 test/test_diff_parser.py | 30 ++++++++++++++++++++++++++++--
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/parso/python/diff.py b/parso/python/diff.py
index 2dcf027..f6c26a0 100644
--- a/parso/python/diff.py
+++ b/parso/python/diff.py
@@ -281,10 +281,19 @@ class DiffParser(object):
             else:
                 p_children = line_stmt.parent.children
                 index = p_children.index(line_stmt)
+                p_children = p_children[index:]
+                # There might be a random dedent where we have to stop copying.
+                # Invalid indents are ok, because the parser handled that
+                # properly before. An invalid dedent can happen, because a few
+                # lines above there was an invalid indent.
+                indentation = line_stmt.start_pos[1]
+                for i, c in enumerate(p_children):
+                    if c.start_pos[1] < indentation:
+                        p_children = p_children[:i]
 
                 from_ = self._nodes_tree.parsed_until_line + 1
                 copied_nodes = self._nodes_tree.copy_nodes(
-                    p_children[index:],
+                    p_children,
                     until_line_old,
                     line_offset
                 )
diff --git a/test/test_diff_parser.py b/test/test_diff_parser.py
index d7e6b89..624d9ea 100644
--- a/test/test_diff_parser.py
+++ b/test/test_diff_parser.py
@@ -845,8 +845,8 @@ def test_indentation_issues(differ):
 
     differ.initialize(code1)
     differ.parse(code2, parsers=2, copies=2, expect_error_leaves=True)
-    differ.parse(code1, copies=2)
-    differ.parse(code3, parsers=2, copies=1)
+    differ.parse(code1, copies=2, parsers=1)
+    differ.parse(code3, parsers=1, copies=1)
     differ.parse(code1, parsers=1, copies=2)
 
 
@@ -1305,3 +1305,29 @@ def test_async_copy(differ):
     differ.initialize(code1)
     differ.parse(code2, copies=1, parsers=1)
     differ.parse(code1, copies=1, parsers=1, expect_error_leaves=True)
+
+
+def test_parent_on_decorator(differ):
+    code1 = dedent('''\
+        class AClass:
+            @decorator()
+                def b_test(self):
+                print("Hello")
+                print("world")
+
+            def a_test(self):
+                pass''')
+    code2 = dedent('''\
+        class AClass:
+            @decorator()
+            def b_test(self):
+                print("Hello")
+                print("world")
+
+            def a_test(self):
+                pass''')
+    differ.initialize(code1)
+    module_node = differ.parse(code2, copies=2, parsers=1)
+    cls = module_node.children[0]
+    cls_suite = cls.children[-1]
+    assert len(cls_suite.children) == 3