From 25ecc328a97987deea440119df77996a3cab6f35 Mon Sep 17 00:00:00 2001
From: Batuhan Taskaya <batuhanosmantaskaya@gmail.com>
Date: Wed, 5 Aug 2020 16:32:32 +0300
Subject: [PATCH] [3.8] bpo-40726: handle uninitalized end_lineno on
 ast.increment_lineno (GH-20312). (cherry picked from commit
 8f4380d2f5839a321475104765221a7394a9d649)

Co-authored-by: Batuhan Taskaya <batuhanosmantaskaya@gmail.com>
---
 Lib/ast.py                                        | 15 ++++++++++++---
 Lib/test/test_ast.py                              | 11 +++++++++++
 .../2020-05-22-12-45-58.bpo-40726.7oBdMw.rst      |  2 ++
 3 files changed, 25 insertions(+), 3 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2020-05-22-12-45-58.bpo-40726.7oBdMw.rst

diff --git a/Lib/ast.py b/Lib/ast.py
index 99a1148a3ba248..52afd0a348a196 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -146,7 +146,13 @@ def copy_location(new_node, old_node):
     for attr in 'lineno', 'col_offset', 'end_lineno', 'end_col_offset':
         if attr in old_node._attributes and attr in new_node._attributes \
            and hasattr(old_node, attr):
-            setattr(new_node, attr, getattr(old_node, attr))
+            value = getattr(old_node, attr, None)
+            # end_lineno and end_col_offset are optional attributes, and they
+            # should be copied whether the value is None or not.
+            if value is not None or (
+                hasattr(old_node, attr) and attr.startswith("end_")
+            ):
+                setattr(new_node, attr, value)
     return new_node
 
 
@@ -194,8 +200,11 @@ def increment_lineno(node, n=1):
     for child in walk(node):
         if 'lineno' in child._attributes:
             child.lineno = getattr(child, 'lineno', 0) + n
-        if 'end_lineno' in child._attributes:
-            child.end_lineno = getattr(child, 'end_lineno', 0) + n
+        if (
+            "end_lineno" in child._attributes
+            and (end_lineno := getattr(child, "end_lineno", 0)) is not None
+        ):
+            child.end_lineno = end_lineno + n
     return node
 
 
diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
index b921f4a5d68269..aa66b4efe33ef3 100644
--- a/Lib/test/test_ast.py
+++ b/Lib/test/test_ast.py
@@ -718,6 +718,12 @@ def test_copy_location(self):
             'lineno=1, col_offset=4, end_lineno=1, end_col_offset=5), lineno=1, '
             'col_offset=0, end_lineno=1, end_col_offset=5))'
         )
+        src = ast.Call(col_offset=1, lineno=1, end_lineno=1, end_col_offset=1)
+        new = ast.copy_location(src, ast.Call(col_offset=None, lineno=None))
+        self.assertIsNone(new.end_lineno)
+        self.assertIsNone(new.end_col_offset)
+        self.assertEqual(new.lineno, 1)
+        self.assertEqual(new.col_offset, 1)
 
     def test_fix_missing_locations(self):
         src = ast.parse('write("spam")')
@@ -757,6 +763,11 @@ def test_increment_lineno(self):
             'lineno=4, col_offset=4, end_lineno=4, end_col_offset=5), lineno=4, '
             'col_offset=0, end_lineno=4, end_col_offset=5))'
         )
+        src = ast.Call(
+            func=ast.Name("test", ast.Load()), args=[], keywords=[], lineno=1
+        )
+        self.assertEqual(ast.increment_lineno(src).lineno, 2)
+        self.assertIsNone(ast.increment_lineno(src).end_lineno)
 
     def test_iter_fields(self):
         node = ast.parse('foo()', mode='eval')
diff --git a/Misc/NEWS.d/next/Library/2020-05-22-12-45-58.bpo-40726.7oBdMw.rst b/Misc/NEWS.d/next/Library/2020-05-22-12-45-58.bpo-40726.7oBdMw.rst
new file mode 100644
index 00000000000000..7409eb3d80df64
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-05-22-12-45-58.bpo-40726.7oBdMw.rst
@@ -0,0 +1,2 @@
+Handle cases where the ``end_lineno`` is ``None`` on
+:func:`ast.increment_lineno`.