[5.1.x] Fixed #35417 -- Updated BaseContext.new() with values to create a context that can be flattened.

Backport of 2a32b233822683c51e59722b7c9aa0789fc4ab1b from main.

3 files changed, 15 insertions, 1 deletions

diff --git a/AUTHORS b/AUTHORS
index 56cda52202..bd86da5b57 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -375,6 +375,7 @@ answer newbie questions, and generally made Django that much better:
     George Karpenkov <george@metaworld.ru>
     George Song <george@damacy.net>
     George Vilches <gav@thataddress.com>
+    George Y. Kussumoto <georgeyk.dev@gmail.com>
     Georg "Hugo" Bauer <gb@hugo.westfalen.de>
     Georgi Stanojevski <glisha@gmail.com>
     Gerardo Orozco <gerardo.orozco.mosqueda@gmail.com>
diff --git a/django/template/context.py b/django/template/context.py
index 080a2dd9c0..0c28b479cd 100644
--- a/django/template/context.py
+++ b/django/template/context.py
@@ -31,7 +31,9 @@ class BaseContext:
     def _reset_dicts(self, value=None):
         builtins = {"True": True, "False": False, "None": None}
         self.dicts = [builtins]
-        if value is not None:
+        if isinstance(value, BaseContext):
+            self.dicts += value.dicts[1:]
+        elif value is not None:
             self.dicts.append(value)
 
     def __copy__(self):
diff --git a/tests/template_tests/test_context.py b/tests/template_tests/test_context.py
index 7420bb4c36..6d8ee7a6e6 100644
--- a/tests/template_tests/test_context.py
+++ b/tests/template_tests/test_context.py
@@ -158,6 +158,17 @@ class ContextTests(SimpleTestCase):
             },
         )
 
+    def test_flatten_context_with_context_copy(self):
+        ctx1 = Context({"a": 2})
+        ctx2 = ctx1.new(Context({"b": 4}))
+        self.assertEqual(
+            ctx2.dicts, [{"True": True, "False": False, "None": None}, {"b": 4}]
+        )
+        self.assertEqual(
+            ctx2.flatten(),
+            {"False": False, "None": None, "True": True, "b": 4},
+        )
+
     def test_context_comparable(self):
         """
         #21765 -- equality comparison should work