Implement OpenAPI Components

Author: gnuletik

docs/api-guide/schemas.md

@@ -316,6 +316,65 @@ class CustomSchema(AutoSchema):
     def get_operation_id(self, path, method):
         pass
 
+class MyView(APIView):
+   schema = AutoSchema(component_name="Ulysses")
+```
+
+### Components
+
+Since DRF 3.12, Schema uses the [OpenAPI Components](openapi-components). This method defines components in the schema and [references them](openapi-reference) inside request and response objects. By default, the component's name is deduced from the Serializer's name.
+
+Using OpenAPI's components provides the following advantages:
+* The schema is more readable and lightweight.
+* If you use the schema to generate an SDK (using [openapi-generator](openapi-generator) or [swagger-codegen](swagger-codegen)). The generator can name your SDK's models.
+
+### Handling component's schema errors
+
+You may get the following error while generating the schema:
+```
+"Serializer" is an invalid class name for schema generation.
+Serializer's class name should be unique and explicit. e.g. "ItemSerializer".
+```
+
+This error occurs when the Serializer name is "Serializer". You should choose a component's name unique across your schema and different than "Serializer".
+
+You may also get the following warning:
+```
+Schema component "ComponentName" has been overriden with a different value.
+```
+
+This warning occurs when different components have the same name in one schema. Your component name should be unique across your project. This is likely an error that may lead to an invalid schema.
+
+You have two ways to solve the previous issues:
+* You can rename your serializer with a unique name and another name than "Serializer".
+* You can set the `component_name` kwarg parameter of the AutoSchema constructor (see below).
+* You can override the `get_component_name` method of the AutoSchema class (see below).
+
+#### Set a custom component's name for your view
+
+To override the component's name in your view, you can use the `component_name` parameter of the AutoSchema constructor:
+
+```python
+from rest_framework.schemas.openapi import AutoSchema
+
+class MyView(APIView):
+   schema = AutoSchema(component_name="Ulysses")
+```
+
+#### Override the default implementation
+
+If you want to have more control and customization about how the schema's components are generated, you can override the `get_component_name` and `get_components` method from the AutoSchema class.
+
+```python
+from rest_framework.schemas.openapi import AutoSchema
+
+class CustomSchema(AutoSchema):
+	def get_components(self, path, method):
+		# Implement your custom implementation
+
+	def get_component_name(self, serializer):
+		# Implement your custom implementation
+
 class CustomView(APIView):
     """APIView subclass with custom schema introspection."""
     schema = CustomSchema()
@@ -326,3 +385,7 @@ class CustomView(APIView):
 [openapi-operation]: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#operationObject
 [openapi-tags]: https://swagger.io/specification/#tagObject
 [openapi-operationid]: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#fixed-fields-17
+[openapi-components]: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#componentsObject
+[openapi-reference]: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#referenceObject
+[openapi-generator]: https://github.com/OpenAPITools/openapi-generator
+[swagger-codegen]: https://github.com/swagger-api/swagger-codegen

rest_framework/schemas/openapi.py

@@ -1,3 +1,4 @@
+import re
 import warnings
 from collections import OrderedDict
 from decimal import Decimal
@@ -65,16 +66,26 @@ def get_schema(self, request=None, public=False):
         Generate a OpenAPI schema.
         """
         self._initialise_endpoints()
+        components_schemas = {}
 
         # Iterate endpoints generating per method path operations.
-        # TODO: …and reference components.
         paths = {}
         _, view_endpoints = self._get_paths_and_endpoints(None if public else request)
         for path, method, view in view_endpoints:
             if not self.has_view_permissions(path, method, view):
                 continue
 
             operation = view.schema.get_operation(path, method)
+            components = view.schema.get_components(path, method)
+            for k in components.keys():
+                if k not in components_schemas:
+                    continue
+                if components_schemas[k] == components[k]:
+                    continue
+                warnings.warn('Schema component "{}" has been overriden with a different value.'.format(k))
+
+            components_schemas.update(components)
+
             # Normalise path for any provided mount url.
             if path.startswith('/'):
                 path = path[1:]
@@ -92,21 +103,28 @@ def get_schema(self, request=None, public=False):
             'paths': paths,
         }
 
+        if len(components_schemas) > 0:
+            schema['components'] = {
+                'schemas': components_schemas
+            }
+
         return schema
 
 # View Inspectors
 
 
 class AutoSchema(ViewInspector):
 
-    def __init__(self, operation_id_base=None, tags=None):
+    def __init__(self, tags=None, operation_id_base=None, component_name=None):
         """
         :param operation_id_base: user-defined name in operationId. If empty, it will be deducted from the Model/Serializer/View name.
+        :param component_name: user-defined component's name. If empty, it will be deducted from the Serializer's class name.
         """
         if tags and not all(isinstance(tag, str) for tag in tags):
             raise ValueError('tags must be a list or tuple of string.')
         self._tags = tags
         self.operation_id_base = operation_id_base
+        self.component_name = component_name
         super().__init__()
 
     request_media_types = []
@@ -140,6 +158,43 @@ def get_operation(self, path, method):
 
         return operation
 
+    def get_component_name(self, serializer):
+        """
+        Compute the component's name from the serializer.
+        Raise an exception if the serializer's class name is "Serializer" (case-insensitive).
+        """
+        if self.component_name is not None:
+            return self.component_name
+
+        # use the serializer's class name as the component name.
+        component_name = serializer.__class__.__name__
+        # We remove the "serializer" string from the class name.
+        pattern = re.compile("serializer", re.IGNORECASE)
+        component_name = pattern.sub("", component_name)
+
+        if component_name == "":
+            raise Exception(
+                '"{}" is an invalid class name for schema generation. '
+                'Serializer\'s class name should be unique and explicit. e.g. "ItemSerializer"'
+                .format(serializer.__class__.__name__)
+            )
+
+        return component_name
+
+    def get_components(self, path, method):
+        """
+        Return components with their properties from the serializer.
+        """
+        serializer = self._get_serializer(path, method)
+
+        if not isinstance(serializer, serializers.Serializer):
+            return {}
+
+        component_name = self.get_component_name(serializer)
+
+        content = self._map_serializer(serializer)
+        return {component_name: content}
+
     def get_operation_id_base(self, path, method, action):
         """
         Compute the base part for operation ID from the model, serializer or view name.
@@ -434,10 +489,6 @@ def _map_min_max(self, field, content):
 
     def _map_serializer(self, serializer):
         # Assuming we have a valid serializer instance.
-        # TODO:
-        #   - field is Nested or List serializer.
-        #   - Handle read_only/write_only for request/response differences.
-        #       - could do this with readOnly/writeOnly and then filter dict.
         required = []
         properties = {}
 
@@ -542,6 +593,9 @@ def _get_serializer(self, path, method):
                           .format(view.__class__.__name__, method, path))
             return None
 
+    def _get_reference(self, serializer):
+        return {'$ref': '#/components/schemas/{}'.format(self.get_component_name(serializer))}
+
     def _get_request_body(self, path, method):
         if method not in ('PUT', 'PATCH', 'POST'):
             return {}
@@ -551,20 +605,13 @@ def _get_request_body(self, path, method):
         serializer = self._get_serializer(path, method)
 
         if not isinstance(serializer, serializers.Serializer):
-            return {}
-
-        content = self._map_serializer(serializer)
-        # No required fields for PATCH
-        if method == 'PATCH':
-            content.pop('required', None)
-        # No read_only fields for request.
-        for name, schema in content['properties'].copy().items():
-            if 'readOnly' in schema:
-                del content['properties'][name]
+            item_schema = {}
+        else:
+            item_schema = self._get_reference(serializer)
 
         return {
             'content': {
-                ct: {'schema': content}
+                ct: {'schema': item_schema}
                 for ct in self.request_media_types
             }
         }
@@ -580,17 +627,12 @@ def _get_responses(self, path, method):
 
         self.response_media_types = self.map_renderers(path, method)
 
-        item_schema = {}
         serializer = self._get_serializer(path, method)
 
-        if isinstance(serializer, serializers.Serializer):
-            item_schema = self._map_serializer(serializer)
-            # No write_only fields for response.
-            for name, schema in item_schema['properties'].copy().items():
-                if 'writeOnly' in schema:
-                    del item_schema['properties'][name]
-                    if 'required' in item_schema:
-                        item_schema['required'] = [f for f in item_schema['required'] if f != name]
+        if not isinstance(serializer, serializers.Serializer):
+            item_schema = {}
+        else:
+            item_schema = self._get_reference(serializer)
 
         if is_list_view(path, method, self.view):
             response_schema = {