gh-86178: Add wsgiref.types (GH-32335)

2 files changed, 56 insertions, 0 deletions

diff --git a/Lib/wsgiref/__init__.py b/Lib/wsgiref/__init__.py
index 1efbba0..59ee48f 100644
--- a/Lib/wsgiref/__init__.py
+++ b/Lib/wsgiref/__init__.py
@@ -13,6 +13,8 @@ Current Contents:
 * validate -- validation wrapper that sits between an app and a server
   to detect errors in either
 
+* types -- collection of WSGI-related types for static type checking
+
 To-Do:
 
 * cgi_gateway -- Run WSGI apps under CGI (pending a deployment standard)
diff --git a/Lib/wsgiref/types.py b/Lib/wsgiref/types.py
new file mode 100644
index 0000000..4a519e5
--- /dev/null
+++ b/Lib/wsgiref/types.py
@@ -0,0 +1,54 @@
+"""WSGI-related types for static type checking"""
+
+from collections.abc import Callable, Iterable
+from types import TracebackType
+from typing import Any, Protocol, TypeAlias
+
+__all__ = [
+    "StartResponse",
+    "WSGIEnvironment",
+    "WSGIApplication",
+    "InputStream",
+    "ErrorStream",
+    "FileWrapper",
+]
+
+_ExcInfo = tuple[type[BaseException], BaseException, TracebackType]
+_OptExcInfo = _ExcInfo | tuple[None, None, None]
+
+class StartResponse(Protocol):
+    """start_response() callable as defined in PEP 3333"""
+    def __call__(
+        self,
+        status: str,
+        headers: list[tuple[str, str]],
+        exc_info: _OptExcInfo | None = ...,
+        /,
+    ) -> Callable[[bytes], object]: ...
+
+WSGIEnvironment: TypeAlias = dict[str, Any]
+WSGIApplication: TypeAlias = Callable[[WSGIEnvironment, StartResponse],
+    Iterable[bytes]]
+
+class InputStream(Protocol):
+    """WSGI input stream as defined in PEP 3333"""
+    def read(self, size: int = ..., /) -> bytes: ...
+    def readline(self, size: int = ..., /) -> bytes: ...
+    def readlines(self, hint: int = ..., /) -> list[bytes]: ...
+    def __iter__(self) -> Iterable[bytes]: ...
+
+class ErrorStream(Protocol):
+    """WSGI error stream as defined in PEP 3333"""
+    def flush(self) -> object: ...
+    def write(self, s: str, /) -> object: ...
+    def writelines(self, seq: list[str], /) -> object: ...
+
+class _Readable(Protocol):
+    def read(self, size: int = ..., /) -> bytes: ...
+    # Optional: def close(self) -> object: ...
+
+class FileWrapper(Protocol):
+    """WSGI file wrapper as defined in PEP 3333"""
+    def __call__(
+        self, file: _Readable, block_size: int = ..., /,
+    ) -> Iterable[bytes]: ...