Add URL converter protocol type (#1984)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>

django-stubs/urls/converters.pyi

@@ -1,6 +1,12 @@
-from typing import Any
+from typing import Any, Protocol
 from uuid import UUID
 
+class _Converter(Protocol):
+    regex: str
+    def __init__(self) -> None: ...
+    def to_python(self, value: str) -> Any: ...
+    def to_url(self, value: Any) -> str: ...
+
 class IntConverter:
     regex: str
     def to_python(self, value: str) -> int: ...
@@ -19,9 +25,9 @@ class UUIDConverter:
 class SlugConverter(StringConverter): ...
 class PathConverter(StringConverter): ...
 
-DEFAULT_CONVERTERS: dict[str, Any]
-REGISTERED_CONVERTERS: dict[str, Any]
+DEFAULT_CONVERTERS: dict[str, _Converter]
+REGISTERED_CONVERTERS: dict[str, _Converter]
 
-def register_converter(converter: type[Any], type_name: str) -> None: ...
-def get_converters() -> dict[str, Any]: ...
-def get_converter(raw_converter: str) -> Any: ...
+def register_converter(converter: type[_Converter], type_name: str) -> None: ...
+def get_converters() -> dict[str, _Converter]: ...
+def get_converter(raw_converter: str) -> _Converter: ...

tests/typecheck/urls/test_converters.yml

@@ -0,0 +1,36 @@
+-   case: test_register_converter_builtin
+    main: |
+      from django.urls import register_converter
+      from django.urls.converters import IntConverter
+
+      register_converter(IntConverter, "bigint")
+
+-   case: test_register_converter_custom
+    main: |
+      from django.urls import register_converter
+
+      class BigIntConverter:
+          regex = r"[0-9]+"
+
+          def to_python(self, value: str) -> int:
+              return int(value)
+
+          def to_url(self, value: int) -> str:
+              return str(value)
+
+      register_converter(BigIntConverter, "bigint")
+
+-   case: test_register_converter_incorrect_types
+    main: |
+      from django.urls import register_converter
+
+      class BigIntConverter:
+          regex = r"[0-9]+"
+
+          def to_python(self, value: int) -> str:
+              return str(value)
+
+          def to_url(self, value: str) -> int:
+              return int(value)
+
+      register_converter(BigIntConverter, "bigint")  # E: Argument 1 to "register_converter" has incompatible type "Type[BigIntConverter]"; expected "Type[_Converter]"  [arg-type]