Load included and related serializers in meta class

CHANGELOG.md

@@ -8,6 +8,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 Note that in line with [Django REST Framework policy](http://www.django-rest-framework.org/topics/release-notes/),
 any parts of the framework not mentioned in the documentation should generally be considered private API, and may be subject to change.
 
+## [Unreleased]
+
+### Changed
+
+* Moved resolving of `included_serialzers` and `related_serializers` classes to serializer's meta class.
+
+### Deprecated
+
+* Deprecated `get_included_serializers(serializer)` function under `rest_framework_json_api.utils`. Use `serializer.included_serializers` instead.
+
 ## [4.2.1] - 2021-07-06
 
 ### Fixed
@@ -40,7 +50,6 @@ any parts of the framework not mentioned in the documentation should generally b
 * Deprecated default `format_type` argument of `rest_framework_json_api.utils.format_value`. Use `rest_framework_json_api.utils.format_field_name` or specify specifc `format_type` instead.
 * Deprecated `format_type` argument of `rest_framework_json_api.utils.format_link_segment`. Use `rest_framework_json_api.utils.format_value` instead.
 
-
 ## [4.1.0] - 2021-03-08
 
 ### Added

rest_framework_json_api/relations.py

@@ -16,7 +16,6 @@
 from rest_framework_json_api.utils import (
     Hyperlink,
     format_link_segment,
-    get_included_serializers,
     get_resource_type_from_instance,
     get_resource_type_from_queryset,
     get_resource_type_from_serializer,
@@ -274,7 +273,7 @@ def get_resource_type_from_included_serializer(self):
                 inflection.singularize(field_name),
                 inflection.pluralize(field_name),
             ]
-            includes = get_included_serializers(parent)
+            includes = getattr(parent, "included_serializers", dict())
             for field in field_names:
                 if field in includes.keys():
                     return get_resource_type_from_serializer(includes[field])

rest_framework_json_api/renderers.py

@@ -284,7 +284,9 @@ def extract_included(
 
         current_serializer = fields.serializer
         context = current_serializer.context
-        included_serializers = utils.get_included_serializers(current_serializer)
+        included_serializers = getattr(
+            current_serializer, "included_serializers", dict()
+        )
         included_resources = copy.copy(included_resources)
         included_resources = [
             inflection.underscore(value) for value in included_resources
@@ -692,8 +694,8 @@ def _get_included_serializers(cls, serializer, prefix="", already_seen=None):
         included_serializers = []
         already_seen.add(serializer)
 
-        for include, included_serializer in utils.get_included_serializers(
-            serializer
+        for include, included_serializer in getattr(
+            serializer, "included_serializers", dict()
         ).items():
             included_serializers.append(f"{prefix}{include}")
             included_serializers.extend(

rest_framework_json_api/schemas/openapi.py

@@ -1,7 +1,6 @@
 import warnings
 from urllib.parse import urljoin
 
-from django.utils.module_loading import import_string as import_class_from_dotted_path
 from rest_framework.fields import empty
 from rest_framework.relations import ManyRelatedField
 from rest_framework.schemas import openapi as drf_openapi
@@ -379,13 +378,7 @@ def _find_related_view(self, view_endpoints, related_serializer, parent_view):
         """
         for path, method, view in view_endpoints:
             view_serializer = view.get_serializer()
-            if not isinstance(related_serializer, type):
-                related_serializer_class = import_class_from_dotted_path(
-                    related_serializer
-                )
-            else:
-                related_serializer_class = related_serializer
-            if isinstance(view_serializer, related_serializer_class):
+            if isinstance(view_serializer, related_serializer):
                 return view
 
         return None

rest_framework_json_api/serializers.py

@@ -1,8 +1,10 @@
 from collections import OrderedDict
+from collections.abc import Mapping
 
 import inflection
 from django.core.exceptions import ObjectDoesNotExist
 from django.db.models.query import QuerySet
+from django.utils.module_loading import import_string as import_class_from_dotted_path
 from django.utils.translation import gettext_lazy as _
 from rest_framework.exceptions import ParseError
 
@@ -22,7 +24,6 @@
 from rest_framework_json_api.relations import ResourceRelatedField
 from rest_framework_json_api.utils import (
     get_included_resources,
-    get_included_serializers,
     get_resource_type_from_instance,
     get_resource_type_from_model,
     get_resource_type_from_serializer,
@@ -120,7 +121,7 @@ def __init__(self, *args, **kwargs):
         view = context.get("view") if context else None
 
         def validate_path(serializer_class, field_path, path):
-            serializers = get_included_serializers(serializer_class)
+            serializers = getattr(serializer_class, "included_serializers", None)
             if serializers is None:
                 raise ParseError("This endpoint does not support the include parameter")
             this_field_name = inflection.underscore(field_path[0])
@@ -152,8 +153,55 @@ def validate_path(serializer_class, field_path, path):
         super(IncludedResourcesValidationMixin, self).__init__(*args, **kwargs)
 
 
+class LazySerializersDict(Mapping):
+    """
+    A dictionary of serializers which lazily import dotted class path and self.
+    """
+
+    def __init__(self, parent, serializers):
+        self.parent = parent
+        self.serializers = serializers
+
+    def __getitem__(self, key):
+        value = self.serializers[key]
+        if not isinstance(value, type):
+            if value == "self":
+                value = self.parent
+            else:
+                value = import_class_from_dotted_path(value)
+            self.serializers[key] = value
+
+        return value
+
+    def __iter__(self):
+        return iter(self.serializers)
+
+    def __len__(self):
+        return len(self.serializers)
+
+    def __repr__(self):
+        return dict.__repr__(self.serializers)
+
+
 class SerializerMetaclass(SerializerMetaclass):
-    pass
+    def __new__(cls, name, bases, attrs):
+        serializer = super().__new__(cls, name, bases, attrs)
+
+        if attrs.get("included_serializers", None):
+            setattr(
+                serializer,
+                "included_serializers",
+                LazySerializersDict(serializer, attrs["included_serializers"]),
+            )
+
+        if attrs.get("related_serializers", None):
+            setattr(
+                serializer,
+                "related_serializers",
+                LazySerializersDict(serializer, attrs["related_serializers"]),
+            )
+
+        return serializer
 
 
 # If user imports serializer from here we can catch class definition and check

rest_framework_json_api/utils.py

@@ -1,4 +1,3 @@
-import copy
 import inspect
 import operator
 import warnings
@@ -13,7 +12,6 @@
 )
 from django.http import Http404
 from django.utils import encoding
-from django.utils.module_loading import import_string as import_class_from_dotted_path
 from django.utils.translation import gettext_lazy as _
 from rest_framework import exceptions
 from rest_framework.exceptions import APIException
@@ -342,20 +340,14 @@ def get_default_included_resources_from_serializer(serializer):
 
 
 def get_included_serializers(serializer):
-    included_serializers = copy.copy(
-        getattr(serializer, "included_serializers", dict())
+    warnings.warn(
+        DeprecationWarning(
+            "Using of `get_included_serializers(serializer)` function is deprecated."
+            "Use `serializer.included_serializers` instead."
+        )
     )
 
-    for name, value in iter(included_serializers.items()):
-        if not isinstance(value, type):
-            if value == "self":
-                included_serializers[name] = (
-                    serializer if isinstance(serializer, type) else serializer.__class__
-                )
-            else:
-                included_serializers[name] = import_class_from_dotted_path(value)
-
-    return included_serializers
+    return getattr(serializer, "included_serializers", dict())
 
 
 def get_relation_instance(resource_instance, source, serializer):

rest_framework_json_api/views.py

@@ -11,7 +11,6 @@
 from django.db.models.manager import Manager
 from django.db.models.query import QuerySet
 from django.urls import NoReverseMatch
-from django.utils.module_loading import import_string as import_class_from_dotted_path
 from rest_framework import generics, viewsets
 from rest_framework.exceptions import MethodNotAllowed, NotFound
 from rest_framework.fields import get_attribute
@@ -183,8 +182,6 @@ def get_related_serializer_class(self):
                     False
                 ), 'Either "included_serializers" or "related_serializers" should be configured'
 
-            if not isinstance(_class, type):
-                return import_class_from_dotted_path(_class)
             return _class
 
         return parent_serializer_class

tests/test_serializers.py

@@ -0,0 +1,35 @@
+from django.db import models
+
+from rest_framework_json_api import serializers
+from tests.models import DJAModel, ManyToManyTarget
+from tests.serializers import ManyToManyTargetSerializer
+
+
+def test_get_included_serializers():
+    class IncludedSerializersModel(DJAModel):
+        self = models.ForeignKey("self", on_delete=models.CASCADE)
+        target = models.ForeignKey(ManyToManyTarget, on_delete=models.CASCADE)
+        other_target = models.ForeignKey(ManyToManyTarget, on_delete=models.CASCADE)
+
+        class Meta:
+            app_label = "tests"
+
+    class IncludedSerializersSerializer(serializers.ModelSerializer):
+        included_serializers = {
+            "self": "self",
+            "target": ManyToManyTargetSerializer,
+            "other_target": "tests.serializers.ManyToManyTargetSerializer",
+        }
+
+        class Meta:
+            model = IncludedSerializersModel
+            fields = ("self", "other_target", "target")
+
+    included_serializers = IncludedSerializersSerializer.included_serializers
+    expected_included_serializers = {
+        "self": IncludedSerializersSerializer,
+        "target": ManyToManyTargetSerializer,
+        "other_target": ManyToManyTargetSerializer,
+    }
+
+    assert included_serializers == expected_included_serializers

tests/test_utils.py

@@ -346,28 +346,32 @@ class PlainRelatedResourceTypeSerializer(serializers.Serializer):
 
 
 def test_get_included_serializers():
-    class IncludedSerializersModel(DJAModel):
+    class DeprecatedIncludedSerializersModel(DJAModel):
         self = models.ForeignKey("self", on_delete=models.CASCADE)
         target = models.ForeignKey(ManyToManyTarget, on_delete=models.CASCADE)
         other_target = models.ForeignKey(ManyToManyTarget, on_delete=models.CASCADE)
 
         class Meta:
             app_label = "tests"
 
-    class IncludedSerializersSerializer(serializers.ModelSerializer):
+    class DeprecatedIncludedSerializersSerializer(serializers.ModelSerializer):
         included_serializers = {
             "self": "self",
             "target": ManyToManyTargetSerializer,
             "other_target": "tests.serializers.ManyToManyTargetSerializer",
         }
 
         class Meta:
-            model = IncludedSerializersModel
+            model = DeprecatedIncludedSerializersModel
             fields = ("self", "other_target", "target")
 
-    included_serializers = get_included_serializers(IncludedSerializersSerializer)
+    with pytest.deprecated_call():
+        included_serializers = get_included_serializers(
+            DeprecatedIncludedSerializersSerializer
+        )
+
     expected_included_serializers = {
-        "self": IncludedSerializersSerializer,
+        "self": DeprecatedIncludedSerializersSerializer,
         "target": ManyToManyTargetSerializer,
         "other_target": ManyToManyTargetSerializer,
     }