higher order hints for @extend_schema_field (case 2) #1174 #1212

drf_spectacular/openapi.py

@@ -628,6 +628,8 @@ def _map_serializer_field(self, field, direction, bypass_extensions=False):
                 schema = build_basic_type(override)
                 if schema is None:
                     return None
+            elif is_higher_order_type_hint(override):
+                schema = resolve_type_hint(override)
             elif isinstance(override, dict):
                 schema = override
             else:

drf_spectacular/plumbing.py

@@ -21,7 +21,6 @@
 else:
     from typing_extensions import TypeGuard  # noqa: F401
 
-
 import inflection
 import uritemplate
 from django.apps import apps
@@ -1366,7 +1365,7 @@ def resolve_type_hint(hint):
     elif origin is collections.abc.Iterable:
         return build_array_type(resolve_type_hint(args[0]))
     else:
-        raise UnableToProceedError()
+        raise UnableToProceedError(hint)
 
 
 def whitelisted(obj: object, classes: Optional[List[Type[object]]], exact=False) -> bool:

drf_spectacular/utils.py

@@ -571,7 +571,7 @@ def get_external_docs(self):
 
 
 def extend_schema_field(
-        field: Union[_SerializerType, _FieldType, OpenApiTypes, _SchemaType],
+        field: Union[_SerializerType, _FieldType, OpenApiTypes, _SchemaType, _KnownPythonTypes],
         component_name: Optional[str] = None
 ) -> Callable[[F], F]:
     """

tests/test_regressions.py

@@ -3348,3 +3348,40 @@ def favorite(self, request, pk=None):
     schema = generate_schema('m', XViewSet)
 
     assert list(schema['paths'].keys()) == ['/m/', '/m/{id}/', '/m/{id}/favorite/']
+
+
+def test_extend_schema_field_with_types(no_warnings):
+    @extend_schema_field(int)
+    class CustomField(serializers.CharField):
+        pass  # pragma: no cover
+
+    @extend_schema_field(typing.List[int])  # this is the new case
+    class CustomField2(serializers.CharField):
+        pass  # pragma: no cover
+
+    class XSerializer(serializers.Serializer):
+        foo = serializers.SerializerMethodField()
+        bar = serializers.SerializerMethodField()
+        baz = CustomField()
+        qux = CustomField2()
+
+        @extend_schema_field(int)
+        def get_foo(self, field, extra_param):
+            return 'foo'  # pragma: no cover
+
+        @extend_schema_field(typing.List[int])
+        def get_bar(self, field, extra_param):
+            return 1  # pragma: no cover
+
+    @extend_schema(request=XSerializer, responses=XSerializer)
+    @api_view(['POST'])
+    def view_func(request, format=None):
+        pass  # pragma: no cover
+
+    schema = generate_schema('/x/', view_function=view_func)
+    assert schema['components']['schemas']['X']['properties'] == {
+        'foo': {'readOnly': True, 'type': 'integer'},
+        'bar': {'items': {'type': 'integer'}, 'readOnly': True, 'type': 'array'},
+        'baz': {'type': 'integer'},
+        'qux': {'items': {'type': 'integer'}, 'type': 'array'}
+    }