revert

Author: max-muoto

stdlib/@tests/test_cases/check_json.py

@@ -2,6 +2,7 @@
 
 import json
 from decimal import Decimal
+from typing import Iterator
 
 
 class _File:
@@ -77,3 +78,38 @@ def custom_encoder(obj: Decimal) -> Decimal:
 
 json.dumps(Decimal(1), default=custom_encoder)  #  type: ignore
 json.dump(Decimal(1), fp, default=custom_encoder)  #  type: ignore
+
+
+# Custom encoders support informing `json.dumps` and `json.dump` about the type of the object.
+class CustomEncoder(json.JSONEncoder):
+    def default(self, obj: str) -> str:
+        return str(obj)
+
+    def encode(self, obj: Decimal) -> str:
+        return str(obj)
+
+    def iterencode(self, obj: Decimal, _one_shot: bool = False) -> Iterator[str]:
+        return iter([str(obj)])
+
+
+# Now, Decimal 1 is supported because of the default method.
+json.dumps(Decimal(1), cls=CustomEncoder)
+json.dump(Decimal(1), fp, cls=CustomEncoder)
+
+
+# If Default didn't support, but encode did that would also work.
+
+
+class CustomEncoder2(json.JSONEncoder):
+    def default(self, obj: str) -> str:
+        return str(obj)
+
+    def encode(self, obj: Decimal) -> str:
+        return str(obj)
+
+    def iterencode(self, obj: Decimal, _one_shot: bool = False) -> Iterator[str]:
+        return iter([str(obj)])
+
+
+json.dumps(Decimal(1), cls=CustomEncoder2)
+json.dump(Decimal(1), fp, cls=CustomEncoder2)

stdlib/json/__init__.pyi

@@ -1,76 +1,54 @@
 from _typeshed import SupportsRead, SupportsWrite
-from collections.abc import Callable, Mapping, Sequence
-from typing import Any, TypeVar, overload
+from collections.abc import Callable, Iterator, Mapping, Sequence
+from typing import Any, Protocol, TypeVar
 from typing_extensions import TypeAlias
 
 from .decoder import JSONDecodeError as JSONDecodeError, JSONDecoder as JSONDecoder
 from .encoder import JSONEncoder as JSONEncoder
 
 __all__ = ["dump", "dumps", "load", "loads", "JSONDecoder", "JSONDecodeError", "JSONEncoder"]
 
-_T = TypeVar("_T")
-
 _JSON: TypeAlias = Mapping[str, _JSON] | Sequence[_JSON] | str | float | bool | None
+_EncodableTypes = TypeVar("_EncodableTypes", default=_JSON)
+_DefaultTypes = TypeVar("_DefaultTypes", default=_JSON)
+_ClsDefaultTypes = TypeVar("_ClsDefaultTypes", default=_JSON)
+
+_EncodableTypes_co = TypeVar("_EncodableTypes_co", covariant=True, default=_JSON)
+_Encode_Fallback_contra = TypeVar("_Encode_Fallback_contra", contravariant=True, default=_JSON)
+
+class _JSONEncoder(Protocol[_EncodableTypes_co, _Encode_Fallback_contra]):
+    """Custom encoder for `json.dumps` and `json.dump`."""
+
+    def encode(self, obj: _EncodableTypes) -> str: ...
+    def iterencode(self, obj: _EncodableTypes, _one_shot: bool = False) -> Iterator[str]: ...
+    def default(self, obj: _Encode_Fallback_contra) -> _EncodableTypes_co: ...
 
-@overload
-def dumps(
-    obj: _JSON,
-    *,
-    skipkeys: bool = False,
-    ensure_ascii: bool = True,
-    check_circular: bool = True,
-    allow_nan: bool = True,
-    cls: type[JSONEncoder] | None = None,
-    indent: None | int | str = None,
-    separators: tuple[str, str] | None = None,
-    default: None = None,
-    sort_keys: bool = False,
-    **kwds: Any,
-) -> str: ...
-@overload
 def dumps(
-    obj: _T,
+    obj: _EncodableTypes | _DefaultTypes | _ClsDefaultTypes,
     *,
     skipkeys: bool = False,
     ensure_ascii: bool = True,
     check_circular: bool = True,
     allow_nan: bool = True,
-    cls: type[JSONEncoder] | None = None,
+    cls: type[_JSONEncoder[_EncodableTypes, _ClsDefaultTypes]] | None = None,
     indent: None | int | str = None,
     separators: tuple[str, str] | None = None,
-    default: Callable[[_T], _JSON],
+    default: Callable[[_DefaultTypes], _EncodableTypes] | None = None,
     sort_keys: bool = False,
     **kwds: Any,
 ) -> str: ...
-@overload
-def dump(
-    obj: _JSON,
-    fp: SupportsWrite[str],
-    *,
-    skipkeys: bool = False,
-    ensure_ascii: bool = True,
-    check_circular: bool = True,
-    allow_nan: bool = True,
-    cls: type[JSONEncoder] | None = None,
-    indent: None | int | str = None,
-    separators: tuple[str, str] | None = None,
-    default: None = None,
-    sort_keys: bool = False,
-    **kwds: Any,
-) -> None: ...
-@overload
 def dump(
-    obj: _T,
+    obj: _EncodableTypes | _DefaultTypes | _ClsDefaultTypes,
     fp: SupportsWrite[str],
     *,
     skipkeys: bool = False,
     ensure_ascii: bool = True,
     check_circular: bool = True,
     allow_nan: bool = True,
-    cls: type[JSONEncoder] | None = None,
+    cls: type[_JSONEncoder[_EncodableTypes, _DefaultTypes]] | None = None,
     indent: None | int | str = None,
     separators: tuple[str, str] | None = None,
-    default: Callable[[_T], _JSON],
+    default: Callable[[_DefaultTypes], _EncodableTypes] | None = None,
     sort_keys: bool = False,
     **kwds: Any,
 ) -> None: ...