fix default for Environment.overlay(enable_async)

CHANGES.rst

@@ -31,6 +31,7 @@ Unreleased
     objects. :issue:`2025`
 -   Fix `copy`/`pickle` support for the internal ``missing`` object.
     :issue:`2027`
+-   ``Environment.overlay(enable_async)`` is applied correctly. :pr:`2061`
 
 
 Version 3.1.4

src/jinja2/environment.py

@@ -406,7 +406,7 @@ def overlay(
         cache_size: int = missing,
         auto_reload: bool = missing,
         bytecode_cache: t.Optional["BytecodeCache"] = missing,
-        enable_async: bool = False,
+        enable_async: bool = missing,
     ) -> "Environment":
         """Create a new overlay environment that shares all the data with the
         current environment except for cache and the overridden attributes.
@@ -419,8 +419,11 @@ def overlay(
         copied over so modifications on the original environment may not shine
         through.
 
+        .. versionchanged:: 3.1.5
+            ``enable_async`` is applied correctly.
+
         .. versionchanged:: 3.1.2
-            Added the ``newline_sequence``,, ``keep_trailing_newline``,
+            Added the ``newline_sequence``, ``keep_trailing_newline``,
             and ``enable_async`` parameters to match ``__init__``.
         """
         args = dict(locals())

tests/test_api.py

@@ -425,3 +425,11 @@ class CustomEnvironment(Environment):
         env = CustomEnvironment()
         tmpl = env.from_string("{{ foo }}")
         assert tmpl.render() == "resolve-foo"
+
+
+def test_overlay_enable_async(env):
+    assert not env.is_async
+    assert not env.overlay().is_async
+    env_async = env.overlay(enable_async=True)
+    assert env_async.is_async
+    assert not env_async.overlay(enable_async=False).is_async