fallback improvements to typing system with typing_extensions

drf_spectacular/plumbing.py

@@ -13,6 +13,11 @@
 from enum import Enum
 from typing import DefaultDict, Generic, List, Optional, Type, TypeVar, Union
 
+if sys.version_info >= (3, 8):
+    from typing import Literal, _TypedDictMeta  # type: ignore[attr-defined]
+else:
+    from typing_extensions import Literal, _TypedDictMeta  # type: ignore[attr-defined]
+
 import inflection
 import uritemplate
 from django.apps import apps
@@ -24,14 +29,13 @@
 from django.db.models.fields.reverse_related import ForeignObjectRel
 from django.db.models.sql.query import Query
 from django.urls.converters import get_converters
-from django.urls.resolvers import (  # type: ignore
+from django.urls.resolvers import (  # type: ignore[attr-defined]
     _PATH_PARAMETER_COMPONENT_RE, RegexPattern, Resolver404, RoutePattern, URLPattern, URLResolver,
     get_resolver,
 )
 from django.utils.functional import Promise, cached_property
 from django.utils.module_loading import import_string
 from django.utils.translation import gettext_lazy as _
-from django.utils.version import PY38
 from rest_framework import exceptions, fields, mixins, serializers, versioning
 from rest_framework.settings import api_settings
 from rest_framework.test import APIRequestFactory
@@ -51,7 +55,7 @@
     class Choices:  # type: ignore
         pass
 
-if PY38:
+if sys.version_info >= (3, 8):
     CACHED_PROPERTY_FUNCS = (functools.cached_property, cached_property)  # type: ignore
 else:
     CACHED_PROPERTY_FUNCS = (cached_property,)  # type: ignore
@@ -478,7 +482,7 @@ def _follow_return_type(a_callable):
     if target_type is None:
         return target_type
     origin, args = _get_type_hint_origin(target_type)
-    if origin is typing.Union:
+    if origin is Union:
         type_args = [arg for arg in args if arg is not type(None)]  # noqa: E721
         if len(type_args) > 1:
             warn(
@@ -1088,8 +1092,9 @@ def resolve_type_hint(hint):
         return build_array_type(resolve_type_hint(args[0]))
     elif origin is frozenset:
         return build_array_type(resolve_type_hint(args[0]))
-    elif hasattr(typing, 'Literal') and origin is typing.Literal:
-        # python >= 3.8
+    elif origin is Literal:
+        # Literal only works for python >= 3.8 despite typing_extensions, because it
+        # behaves slightly different w.r.t. __origin__
         schema = {'enum': list(args)}
         if all(type(args[0]) is type(choice) for choice in args):
             schema.update(build_basic_type(type(args[0])))
@@ -1100,13 +1105,13 @@ def resolve_type_hint(hint):
         if mixin_base_types:
             schema.update(build_basic_type(mixin_base_types[0]))
         return schema
-    elif hasattr(typing, 'TypedDict') and isinstance(hint, typing._TypedDictMeta):
+    elif isinstance(hint, _TypedDictMeta):
         return build_object_type(
             properties={
                 k: resolve_type_hint(v) for k, v in get_type_hints(hint).items()
             }
         )
-    elif origin is typing.Union:
+    elif origin is Union:
         type_args = [arg for arg in args if arg is not type(None)]  # noqa: E721
         if len(type_args) > 1:
             schema = {'oneOf': [resolve_type_hint(arg) for arg in type_args]}

drf_spectacular/utils.py

@@ -1,5 +1,6 @@
 import functools
 import inspect
+import sys
 from typing import Any, Callable, Dict, List, Optional, Type, TypeVar, Union
 
 from rest_framework.fields import Field, empty
@@ -9,8 +10,16 @@
 from drf_spectacular.drainage import error, get_view_methods, set_override, warn
 from drf_spectacular.types import OpenApiTypes, _KnownPythonTypes
 
+if sys.version_info >= (3, 8):
+    from typing import Final, Literal
+else:
+    from typing_extensions import Final, Literal
+
+
 _SerializerType = Union[Serializer, Type[Serializer]]
 
+_ParameterLocationType = Literal['query', 'path', 'header', 'cookie']
+
 
 class PolymorphicProxySerializer(Serializer):
     """
@@ -125,16 +134,16 @@ class OpenApiParameter(OpenApiSchemaBase):
     For valid ``style`` choices please consult the
     `OpenAPI specification <https://swagger.io/specification/#style-values>`_.
     """
-    QUERY = 'query'
-    PATH = 'path'
-    HEADER = 'header'
-    COOKIE = 'cookie'
+    QUERY: Final = 'query'
+    PATH: Final = 'path'
+    HEADER: Final = 'header'
+    COOKIE: Final = 'cookie'
 
     def __init__(
             self,
             name: str,
             type: Union[_SerializerType, _KnownPythonTypes, OpenApiTypes, dict] = str,
-            location: str = QUERY,
+            location: _ParameterLocationType = QUERY,
             required: bool = False,
             description: str = '',
             enum: Optional[List[Any]] = None,

requirements/base.txt

@@ -3,4 +3,5 @@ djangorestframework>=3.10
 uritemplate>=2.0.0
 PyYAML>=5.1
 jsonschema>=2.6.0
-inflection>=0.3.1
+inflection>=0.3.1
+typing-extensions; python_version < "3.8"

setup.py

@@ -19,7 +19,7 @@
     long_description = readme.read()
 
 with open('requirements/base.txt') as fh:
-    requirements = [r for r in fh.read().split() if not r.startswith('#')]
+    requirements = [r for r in fh.read().split('\n') if not r.startswith('#')]
 
 
 def get_version(package):

tests/test_fields.py

@@ -1,5 +1,6 @@
 import functools
 import json
+import sys
 import tempfile
 import uuid
 from datetime import timedelta
@@ -20,14 +21,14 @@
 from drf_spectacular.generators import SchemaGenerator
 from tests import assert_equal, assert_schema, build_absolute_file_path
 
-try:
-    functools_cached_property = functools.cached_property  # type: ignore
-except AttributeError:
-    # functools.cached_property is only available in Python 3.8+.
+if sys.version_info >= (3, 8):
+    functools_cached_property = functools.cached_property
+else:
     # We re-use Django's cached_property when it's not avaiable to
     # keep tests unified across Python versions.
     functools_cached_property = cached_property
 
+
 fs = FileSystemStorage(location=tempfile.gettempdir())
 
 

tests/test_plumbing.py

@@ -21,6 +21,11 @@
 from drf_spectacular.validation import validate_schema
 from tests import generate_schema
 
+if sys.version_info >= (3, 8):
+    from typing import TypedDict
+else:
+    from typing_extensions import TypedDict
+
 
 def test_is_serializer():
     assert not is_serializer(serializers.SlugField)
@@ -86,6 +91,9 @@ def test_detype_patterns_with_module_includes(no_warnings):
     )
 
 
+NamedTupleA = collections.namedtuple("NamedTupleA", "a, b")
+
+
 class NamedTupleB(typing.NamedTuple):
     a: int
     b: str
@@ -103,6 +111,10 @@ class InvalidLanguageEnum(Enum):
     DE = 'de'
 
 
+TD1 = TypedDict('TD1', {"foo": int, "bar": typing.List[str]})
+TD2 = TypedDict('TD2', {"foo": str, "bar": typing.Dict[str, int]})
+
+
 TYPE_HINT_TEST_PARAMS = [
     (
         typing.Optional[int],
@@ -152,6 +164,34 @@ class InvalidLanguageEnum(Enum):
     ), (
         InvalidLanguageEnum,
         {'enum': ['en', 'de']}
+    ), (
+        TD1,
+        {
+            'type': 'object',
+            'properties': {
+                'foo': {'type': 'integer'},
+                'bar': {'type': 'array', 'items': {'type': 'string'}}
+            }
+        }
+    ), (
+        typing.List[TD2],
+        {
+            'type': 'array',
+            'items': {
+                'type': 'object',
+                'properties': {
+                    'foo': {'type': 'string'},
+                    'bar': {'type': 'object', 'additionalProperties': {'type': 'integer'}}
+                }
+            }
+        }
+    ), (
+        NamedTupleB,
+        {
+            'type': 'object',
+            'properties': {'a': {'type': 'integer'}, 'b': {'type': 'string'}},
+            'required': ['a', 'b']
+        }
     )
 ]
 
@@ -170,50 +210,20 @@ class LanguageChoices(TextChoices):
 
 if sys.version_info >= (3, 7):
     TYPE_HINT_TEST_PARAMS.append((
-        typing.Iterable[collections.namedtuple("NamedTupleA", "a, b")],  # noqa
+        typing.Iterable[NamedTupleA],
         {
             'type': 'array',
             'items': {'type': 'object', 'properties': {'a': {}, 'b': {}}, 'required': ['a', 'b']}
         }
     ))
-    TYPE_HINT_TEST_PARAMS.append((
-        NamedTupleB,
-        {
-            'type': 'object',
-            'properties': {'a': {'type': 'integer'}, 'b': {'type': 'string'}},
-            'required': ['a', 'b']
-        }
-    ))
 
 if sys.version_info >= (3, 8):
+    # Literal only works for python >= 3.8 despite typing_extensions, because it
+    # behaves slightly different w.r.t. __origin__
     TYPE_HINT_TEST_PARAMS.append((
         typing.Literal['x', 'y'],
         {'enum': ['x', 'y'], 'type': 'string'}
     ))
-    TYPE_HINT_TEST_PARAMS.append((
-        typing.TypedDict('TD', foo=int, bar=typing.List[str]),
-        {
-            'type': 'object',
-            'properties': {
-                'foo': {'type': 'integer'},
-                'bar': {'type': 'array', 'items': {'type': 'string'}}
-            }
-        }
-    ))
-    TYPE_HINT_TEST_PARAMS.append((
-        typing.List[typing.TypedDict('TD', foo=str, bar=typing.Dict[str, int])],  # noqa: F821
-        {
-            'type': 'array',
-            'items': {
-                'type': 'object',
-                'properties': {
-                    'foo': {'type': 'string'},
-                    'bar': {'type': 'object', 'additionalProperties': {'type': 'integer'}}
-                }
-            }
-        }
-    ))
-
 
 if sys.version_info >= (3, 9):
     TYPE_HINT_TEST_PARAMS.append((

tox.ini

@@ -83,7 +83,7 @@ use_parentheses = true
 include_trailing_comma = true
 
 [mypy]
-python_version = 3.6
+python_version = 3.8
 plugins = mypy_django_plugin.main,mypy_drf_plugin.main
 
 [mypy.plugins.django-stubs]