ensure undefined marker access on Jinja getattr->getitem fallback (#85688)

Co-authored-by: Matt Clay <matt@mystile.com>

changelogs/fragments/getattr_marker_access.yml

@@ -0,0 +1,4 @@
+bugfixes:
+  - templating - Undefined marker values sourced from the Jinja ``getattr->getitem`` fallback are now accessed correctly,
+    raising AnsibleUndefinedVariable for user plugins that do not understand markers.
+    Previously, these values were erroneously returned to user plugin code that had not opted in to marker acceptance.

lib/ansible/_internal/_templating/_jinja_bits.py

@@ -811,7 +811,7 @@ class AnsibleEnvironment(SandboxedEnvironment):
             try:
                 value = obj[attribute]
             except (TypeError, LookupError):
-                return self.undefined(obj=obj, name=attribute) if is_safe else self.unsafe_undefined(obj, attribute)
+                value = self.undefined(obj=obj, name=attribute) if is_safe else self.unsafe_undefined(obj, attribute)
 
         AnsibleAccessContext.current().access(value)
 

test/units/_internal/templating/test_jinja_bits.py

@@ -12,7 +12,7 @@ import pytest_mock
 from ansible.errors import AnsibleUndefinedVariable, AnsibleTemplateError
 from ansible._internal._templating._errors import AnsibleTemplatePluginRuntimeError
 from ansible.module_utils._internal._datatag import AnsibleTaggedObject
-from ansible._internal._templating._jinja_common import CapturedExceptionMarker, MarkerError, Marker, UndefinedMarker
+from ansible._internal._templating._jinja_common import CapturedExceptionMarker, MarkerError, Marker, UndefinedMarker, JinjaCallContext
 from ansible._internal._templating._utils import TemplateContext
 from ansible._internal._datatag._tags import TrustedAsTemplate
 from ansible._internal._templating._jinja_bits import (AnsibleEnvironment, TemplateOverrides, _TEMPLATE_OVERRIDE_FIELD_NAMES, defer_template_error,
@@ -443,3 +443,17 @@ def test_mutation_methods(template: str, result: object) -> None:
     This feature may be deprecated and removed in a future release by using Jinja's ImmutableSandboxedEnvironment.
     """
     assert TemplateEngine().template(TRUST.tag(template)) == result
+
+
+@pytest.mark.parametrize("template", (
+    '{{ adict["bogus"] | default("ok") }}',
+    '{{ adict.bogus | default("ok") }}',
+))
+def test_marker_access_getattr_and_getitem(template: str) -> None:
+    """Ensure that getattr and getitem always access markers."""
+    # the absence of a JinjaCallContext should cause the access done by getattr and getitem not to trip when a marker is encountered
+    assert TemplateEngine(variables=dict(adict={})).template(TRUST.tag(template)) == "ok"
+
+    with pytest.raises(AnsibleUndefinedVariable):
+        with JinjaCallContext(accept_lazy_markers=False):  # the access done by getattr and getitem should immediately trip when a marker is encountered
+            TemplateEngine(variables=dict(adict={})).template(TRUST.tag(template))