Fix filter plugin result processing (#85653)

changelogs/fragments/templating-filter-generators.yml

@@ -0,0 +1,3 @@
+bugfixes:
+  - templating - Ensure filter plugin result processing occurs under the correct call context.
+    (https://github.com/ansible/ansible/issues/85585)

lib/ansible/_internal/_templating/_jinja_plugins.py

@@ -114,7 +114,13 @@ class JinjaPluginIntercept(c.MutableMapping):
 
         try:
             with JinjaCallContext(accept_lazy_markers=instance.accept_lazy_markers):
-                return instance.j2_function(*lazify_container_args(args), **lazify_container_kwargs(kwargs))
+                result = instance.j2_function(*lazify_container_args(args), **lazify_container_kwargs(kwargs))
+
+                if instance.plugin_type == 'filter':
+                    # ensure list conversion occurs under the call context
+                    result = _wrap_plugin_output(result)
+
+                return result
         except MarkerError as ex:
             return ex.source
         except Exception as ex:
@@ -155,7 +161,6 @@ class JinjaPluginIntercept(c.MutableMapping):
         @functools.wraps(instance.j2_function)
         def wrapper(*args, **kwargs) -> t.Any:
             result = self._invoke_plugin(instance, *args, **kwargs)
-            result = _wrap_plugin_output(result)
 
             return result
 

test/units/_internal/templating/test_templar.py

@@ -1078,3 +1078,18 @@ def test_marker_from_test_plugin() -> None:
     """Verify test plugins can raise MarkerError to return a Marker, and that no warnings or deprecations are emitted."""
     with emits_warnings(deprecation_pattern=[], warning_pattern=[]):
         assert TemplateEngine(variables=dict(something=TRUST.tag("{{ nope }}"))).template(TRUST.tag("{{ (something is eq {}) is undefined }}"))
+
+
+def test_filter_generator() -> None:
+    """Verify that filters which return a generator are converted to a list while under the filter's JinjaCallContext."""
+    variables = dict(
+        foo=[
+            dict(x=1, optional_var=0),
+            dict(x=2),
+        ],
+        bar=TRUST.tag("{{ foo | selectattr('optional_var', 'defined') }}"),
+    )
+
+    te = TemplateEngine(variables=variables)
+    te.template(TRUST.tag("{{ bar }}"))
+    te.template(TRUST.tag("{{ lookup('vars', 'bar') }}"))