fix: errata 8471 - group membership ref type is only group

Author: azmeuk

doc/changelog.rst

@@ -8,6 +8,7 @@ Fixed
 ^^^^^
 - Fix ``model_json_schema()`` generation for models containing :class:`~scim2_models.Reference` or :class:`~scim2_models.Path` fields. :issue:`125`
 - Group ``displayName`` is required. :rfc:`7643` `erratum 5368 <https://www.rfc-editor.org/errata/eid5368>`_ :issue:`123` :pr:`128`
+- :class:`~scim2_models.GroupMembership` ``$ref`` only references ``Group``. :rfc:`7643` `erratum 8471 <https://www.rfc-editor.org/errata/eid8471>`_
 
 [0.6.2] - 2026-01-25
 --------------------

samples/rfc7643-8.7.1-schema-user.json

@@ -572,7 +572,6 @@
                     "name": "$ref",
                     "type": "reference",
                     "referenceTypes": [
-                        "User",
                         "Group"
                     ],
                     "multiValued": false,

scim2_models/resources/user.py

@@ -2,7 +2,6 @@
 from typing import TYPE_CHECKING
 from typing import Annotated
 from typing import ClassVar
-from typing import Union
 
 from pydantic import Base64Bytes
 from pydantic import EmailStr
@@ -202,8 +201,8 @@ class GroupMembership(ComplexAttribute):
     value: Annotated[str | None, Mutability.read_only] = None
     """The identifier of the User's group."""
 
-    ref: Annotated[  # type: ignore[type-arg]
-        Reference[Union["User", "Group"]] | None,
+    ref: Annotated[
+        Reference["Group"] | None,
         Mutability.read_only,
     ] = Field(None, serialization_alias="$ref")
     """The reference URI of a target resource, if the attribute is a

tests/test_dynamic_resources.py

@@ -857,9 +857,7 @@ def test_make_user_model_from_schema(load_sample):
     assert Groups.get_field_annotation("value", Uniqueness) == Uniqueness.none
 
     # group.ref
-    assert (
-        Groups.get_field_root_type("ref") == Reference[Union["User", "Group"]]  # noqa: F821
-    )
+    assert Groups.get_field_root_type("ref") == Reference["Group"]  # noqa: F821
     assert not Groups.get_field_multiplicity("ref")
     assert (
         Groups.model_fields["ref"].description