Add type overloads for recv and recv_streaming.

Fix #1578.

Author: aaugustin

docs/project/changelog.rst

@@ -38,6 +38,12 @@ New features
 * Added :doc:`keepalive and latency measurement <../topics/keepalive>` to the
   :mod:`threading` implementation.
 
+Improvements
+............
+
+* Added type overloads for the ``decode`` argument of
+  :meth:`~asyncio.connection.Connection.recv`. This may simplify static typing.
+
 .. _14.2:
 
 14.2

pyproject.toml

@@ -70,6 +70,7 @@ exclude_lines = [
     "if typing.TYPE_CHECKING:",
     "raise AssertionError",
     "self.fail\\(\".*\"\\)",
+    "@overload",
     "@unittest.skip",
 ]
 partial_branches = [

src/websockets/asyncio/connection.py

@@ -11,7 +11,7 @@
 import uuid
 from collections.abc import AsyncIterable, AsyncIterator, Awaitable, Iterable, Mapping
 from types import TracebackType
-from typing import Any, cast
+from typing import Any, Literal, cast, overload
 
 from ..exceptions import (
     ConcurrencyError,
@@ -243,6 +243,15 @@ async def __aiter__(self) -> AsyncIterator[Data]:
         except ConnectionClosedOK:
             return
 
+    @overload
+    async def recv(self, decode: Literal[True]) -> str: ...
+
+    @overload
+    async def recv(self, decode: Literal[False]) -> bytes: ...
+
+    @overload
+    async def recv(self, decode: bool | None = None) -> Data: ...
+
     async def recv(self, decode: bool | None = None) -> Data:
         """
         Receive the next message.
@@ -312,6 +321,15 @@ async def recv(self, decode: bool | None = None) -> Data:
         await asyncio.shield(self.connection_lost_waiter)
         raise self.protocol.close_exc from self.recv_exc
 
+    @overload
+    def recv_streaming(self, decode: Literal[True]) -> AsyncIterator[str]: ...
+
+    @overload
+    def recv_streaming(self, decode: Literal[False]) -> AsyncIterator[bytes]: ...
+
+    @overload
+    def recv_streaming(self, decode: bool | None = None) -> AsyncIterator[Data]: ...
+
     async def recv_streaming(self, decode: bool | None = None) -> AsyncIterator[Data]:
         """
         Receive the next message frame by frame.

src/websockets/asyncio/messages.py

@@ -4,7 +4,7 @@
 import codecs
 import collections
 from collections.abc import AsyncIterator, Iterable
-from typing import Any, Callable, Generic, TypeVar
+from typing import Any, Callable, Generic, Literal, TypeVar, overload
 
 from ..exceptions import ConcurrencyError
 from ..frames import OP_BINARY, OP_CONT, OP_TEXT, Frame
@@ -116,6 +116,15 @@ def __init__(  # pragma: no cover
         # This flag marks the end of the connection.
         self.closed = False
 
+    @overload
+    async def get(self, decode: Literal[True]) -> str: ...
+
+    @overload
+    async def get(self, decode: Literal[False]) -> bytes: ...
+
+    @overload
+    async def get(self, decode: bool | None = None) -> Data: ...
+
     async def get(self, decode: bool | None = None) -> Data:
         """
         Read the next message.
@@ -176,6 +185,15 @@ async def get(self, decode: bool | None = None) -> Data:
         else:
             return data
 
+    @overload
+    def get_iter(self, decode: Literal[True]) -> AsyncIterator[str]: ...
+
+    @overload
+    def get_iter(self, decode: Literal[False]) -> AsyncIterator[bytes]: ...
+
+    @overload
+    def get_iter(self, decode: bool | None = None) -> AsyncIterator[Data]: ...
+
     async def get_iter(self, decode: bool | None = None) -> AsyncIterator[Data]:
         """
         Stream the next message.

src/websockets/sync/connection.py

@@ -10,7 +10,7 @@
 import uuid
 from collections.abc import Iterable, Iterator, Mapping
 from types import TracebackType
-from typing import Any
+from typing import Any, Literal, overload
 
 from ..exceptions import (
     ConcurrencyError,
@@ -241,6 +241,28 @@ def __iter__(self) -> Iterator[Data]:
         except ConnectionClosedOK:
             return
 
+    # This overload structure is required to avoid the error:
+    # "parameter without a default follows parameter with a default"
+
+    @overload
+    def recv(self, timeout: float | None, decode: Literal[True]) -> str: ...
+
+    @overload
+    def recv(self, timeout: float | None, decode: Literal[False]) -> bytes: ...
+
+    @overload
+    def recv(self, timeout: float | None = None, *, decode: Literal[True]) -> str: ...
+
+    @overload
+    def recv(
+        self, timeout: float | None = None, *, decode: Literal[False]
+    ) -> bytes: ...
+
+    @overload
+    def recv(
+        self, timeout: float | None = None, decode: bool | None = None
+    ) -> Data: ...
+
     def recv(self, timeout: float | None = None, decode: bool | None = None) -> Data:
         """
         Receive the next message.
@@ -311,6 +333,15 @@ def recv(self, timeout: float | None = None, decode: bool | None = None) -> Data
         self.recv_events_thread.join()
         raise self.protocol.close_exc from self.recv_exc
 
+    @overload
+    def recv_streaming(self, decode: Literal[True]) -> Iterator[str]: ...
+
+    @overload
+    def recv_streaming(self, decode: Literal[False]) -> Iterator[bytes]: ...
+
+    @overload
+    def recv_streaming(self, decode: bool | None = None) -> Iterator[Data]: ...
+
     def recv_streaming(self, decode: bool | None = None) -> Iterator[Data]:
         """
         Receive the next message frame by frame.

src/websockets/sync/messages.py

@@ -3,7 +3,7 @@
 import codecs
 import queue
 import threading
-from typing import Any, Callable, Iterable, Iterator
+from typing import Any, Callable, Iterable, Iterator, Literal, overload
 
 from ..exceptions import ConcurrencyError
 from ..frames import OP_BINARY, OP_CONT, OP_TEXT, Frame
@@ -110,6 +110,24 @@ def reset_queue(self, frames: Iterable[Frame]) -> None:
             for frame in queued:  # pragma: no cover
                 self.frames.put(frame)
 
+    # This overload structure is required to avoid the error:
+    # "parameter without a default follows parameter with a default"
+
+    @overload
+    def get(self, timeout: float | None, decode: Literal[True]) -> str: ...
+
+    @overload
+    def get(self, timeout: float | None, decode: Literal[False]) -> bytes: ...
+
+    @overload
+    def get(self, timeout: float | None = None, *, decode: Literal[True]) -> str: ...
+
+    @overload
+    def get(self, timeout: float | None = None, *, decode: Literal[False]) -> bytes: ...
+
+    @overload
+    def get(self, timeout: float | None = None, decode: bool | None = None) -> Data: ...
+
     def get(self, timeout: float | None = None, decode: bool | None = None) -> Data:
         """
         Read the next message.
@@ -181,6 +199,15 @@ def get(self, timeout: float | None = None, decode: bool | None = None) -> Data:
         else:
             return data
 
+    @overload
+    def get_iter(self, decode: Literal[True]) -> Iterator[str]: ...
+
+    @overload
+    def get_iter(self, decode: Literal[False]) -> Iterator[bytes]: ...
+
+    @overload
+    def get_iter(self, decode: bool | None = None) -> Iterator[Data]: ...
+
     def get_iter(self, decode: bool | None = None) -> Iterator[Data]:
         """
         Stream the next message.