fix: extend_schema_field with dict param and oas 3.1

the dict was being mutated, so every subsequent use of the field would have more stuff appended to the schema

drf_spectacular/plumbing.py

@@ -1,4 +1,5 @@
 import collections
+import copy
 import functools
 import hashlib
 import inspect
@@ -525,6 +526,9 @@ def safe_ref(schema: _SchemaType) -> _SchemaType:
 
 def append_meta(schema: _SchemaType, meta: _SchemaType) -> _SchemaType:
     if spectacular_settings.OAS_VERSION.startswith('3.1'):
+        schema = copy.deepcopy(schema)
+        meta = copy.deepcopy(meta)
+
         schema_nullable = meta.pop('nullable', None)
         meta_nullable = schema.pop('nullable', None)
 

tests/test_extend_schema.py

@@ -232,6 +232,28 @@ def test_extend_schema(no_warnings):
     )
 
 
+@mock.patch('drf_spectacular.settings.spectacular_settings.OAS_VERSION', '3.1.0')
+def test_extend_schema_field_with_dict_oas_3_1(no_warnings):
+    @extend_schema_field({"type": "string"})
+    class CustomField(serializers.CharField):
+        pass
+
+    class XSerializer(serializers.Serializer):
+        field1 = CustomField(read_only=True, allow_null=True)
+        field2 = CustomField(read_only=True, allow_null=True)
+        field3 = CustomField(read_only=True, allow_null=True)
+
+    @extend_schema(request=XSerializer, responses=XSerializer)
+    @api_view(['POST'])
+    def view_func(request, format=None):
+        pass  # pragma: no cover
+
+    assert_schema(
+        generate_schema('x', view_function=view_func),
+        'tests/test_extend_schema_field_with_dict_oas_3_1.yml'
+    )
+
+
 def test_layered_extend_schema_on_view_and_method_with_meta(no_warnings):
     class XSerializer(serializers.Serializer):
         field = serializers.IntegerField()

tests/test_extend_schema_field_with_dict_oas_3_1.yml

@@ -0,0 +1,64 @@
+openapi: 3.1.0
+info:
+  title: ''
+  version: 0.0.0
+paths:
+  /x:
+    post:
+      operationId: x_create
+      tags:
+      - x
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/X'
+          application/x-www-form-urlencoded:
+            schema:
+              $ref: '#/components/schemas/X'
+          multipart/form-data:
+            schema:
+              $ref: '#/components/schemas/X'
+      security:
+      - cookieAuth: []
+      - basicAuth: []
+      - {}
+      responses:
+        '200':
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/X'
+          description: ''
+components:
+  schemas:
+    X:
+      type: object
+      properties:
+        field1:
+          type:
+          - string
+          - 'null'
+          readOnly: true
+        field2:
+          type:
+          - string
+          - 'null'
+          readOnly: true
+        field3:
+          type:
+          - string
+          - 'null'
+          readOnly: true
+      required:
+      - field1
+      - field2
+      - field3
+  securitySchemes:
+    basicAuth:
+      type: http
+      scheme: basic
+    cookieAuth:
+      type: apiKey
+      in: cookie
+      name: sessionid