pickle: use protocols instead of IO[bytes] (#6101)

Author: PeterJCLaw

stdlib/pickle.pyi

@@ -1,11 +1,18 @@
 import sys
-from typing import IO, Any, Callable, ClassVar, Iterable, Iterator, Mapping, Optional, Tuple, Type, Union
+from typing import Any, Callable, ClassVar, Iterable, Iterator, Mapping, Optional, Protocol, Tuple, Type, Union
 
 HIGHEST_PROTOCOL: int
 DEFAULT_PROTOCOL: int
 
 bytes_types: Tuple[Type[Any], ...]  # undocumented
 
+class _ReadableFileobj(Protocol):
+    def read(self, __n: int) -> bytes: ...
+    def readline(self) -> bytes: ...
+
+class _WritableFileobj(Protocol):
+    def write(self, __b: bytes) -> Any: ...
+
 if sys.version_info >= (3, 8):
     # TODO: holistic design for buffer interface (typing.Buffer?)
     class PickleBuffer:
@@ -15,22 +22,32 @@ if sys.version_info >= (3, 8):
         def release(self) -> None: ...
     _BufferCallback = Optional[Callable[[PickleBuffer], Any]]
     def dump(
-        obj: Any, file: IO[bytes], protocol: int | None = ..., *, fix_imports: bool = ..., buffer_callback: _BufferCallback = ...
+        obj: Any,
+        file: _WritableFileobj,
+        protocol: int | None = ...,
+        *,
+        fix_imports: bool = ...,
+        buffer_callback: _BufferCallback = ...,
     ) -> None: ...
     def dumps(
         obj: Any, protocol: int | None = ..., *, fix_imports: bool = ..., buffer_callback: _BufferCallback = ...
     ) -> bytes: ...
     def load(
-        file: IO[bytes], *, fix_imports: bool = ..., encoding: str = ..., errors: str = ..., buffers: Iterable[Any] | None = ...
+        file: _ReadableFileobj,
+        *,
+        fix_imports: bool = ...,
+        encoding: str = ...,
+        errors: str = ...,
+        buffers: Iterable[Any] | None = ...,
     ) -> Any: ...
     def loads(
         __data: bytes, *, fix_imports: bool = ..., encoding: str = ..., errors: str = ..., buffers: Iterable[Any] | None = ...
     ) -> Any: ...
 
 else:
-    def dump(obj: Any, file: IO[bytes], protocol: int | None = ..., *, fix_imports: bool = ...) -> None: ...
+    def dump(obj: Any, file: _WritableFileobj, protocol: int | None = ..., *, fix_imports: bool = ...) -> None: ...
     def dumps(obj: Any, protocol: int | None = ..., *, fix_imports: bool = ...) -> bytes: ...
-    def load(file: IO[bytes], *, fix_imports: bool = ..., encoding: str = ..., errors: str = ...) -> Any: ...
+    def load(file: _ReadableFileobj, *, fix_imports: bool = ..., encoding: str = ..., errors: str = ...) -> Any: ...
     def loads(data: bytes, *, fix_imports: bool = ..., encoding: str = ..., errors: str = ...) -> Any: ...
 
 class PickleError(Exception): ...
@@ -53,11 +70,16 @@ class Pickler:
 
     if sys.version_info >= (3, 8):
         def __init__(
-            self, file: IO[bytes], protocol: int | None = ..., *, fix_imports: bool = ..., buffer_callback: _BufferCallback = ...
+            self,
+            file: _WritableFileobj,
+            protocol: int | None = ...,
+            *,
+            fix_imports: bool = ...,
+            buffer_callback: _BufferCallback = ...,
         ) -> None: ...
         def reducer_override(self, obj: Any) -> Any: ...
     else:
-        def __init__(self, file: IO[bytes], protocol: int | None = ..., *, fix_imports: bool = ...) -> None: ...
+        def __init__(self, file: _WritableFileobj, protocol: int | None = ..., *, fix_imports: bool = ...) -> None: ...
     def dump(self, __obj: Any) -> None: ...
     def clear_memo(self) -> None: ...
     def persistent_id(self, obj: Any) -> Any: ...
@@ -68,15 +90,17 @@ class Unpickler:
     if sys.version_info >= (3, 8):
         def __init__(
             self,
-            file: IO[bytes],
+            file: _ReadableFileobj,
             *,
             fix_imports: bool = ...,
             encoding: str = ...,
             errors: str = ...,
             buffers: Iterable[Any] | None = ...,
         ) -> None: ...
     else:
-        def __init__(self, file: IO[bytes], *, fix_imports: bool = ..., encoding: str = ..., errors: str = ...) -> None: ...
+        def __init__(
+            self, file: _ReadableFileobj, *, fix_imports: bool = ..., encoding: str = ..., errors: str = ...
+        ) -> None: ...
     def load(self) -> Any: ...
     def find_class(self, __module_name: str, __global_name: str) -> Any: ...
     def persistent_load(self, pid: Any) -> Any: ...