Add missing docstrings for documented public APIs

Addresses #3221 by adding docstrings to all items that appear in the
Sphinx documentation but previously had no docstring:

- MemorySendChannel, MemoryReceiveChannel, MemoryChannelStatistics
  class docstrings
- SocketStream.send_all, .receive_some, .send_eof,
  .wait_send_all_might_not_block, .aclose referencing parent ABCs
- HasFileno.fileno docstring
- ParkingLot.broken_by attribute docstring

Also removes :undoc-members: from the SocketStream autoclass directive
since all methods now have docstrings.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: veeceey

docs/source/reference-io.rst

@@ -218,7 +218,6 @@ abstraction.
 
 .. autoclass:: SocketStream
    :members:
-   :undoc-members:
    :show-inheritance:
 
 .. autoclass:: SocketListener

newsfragments/3221.doc.rst

@@ -0,0 +1,3 @@
+Added missing docstrings for `MemorySendChannel`, `MemoryReceiveChannel`,
+`MemoryChannelStatistics`, ``SocketStream`` methods, `~trio.lowlevel.ParkingLot.broken_by`,
+and ``HasFileno.fileno``.

src/trio/_channel.py

@@ -118,6 +118,12 @@ def __init__(self, max_buffer_size: int | float) -> None:  # noqa: PYI041
 
 @attrs.frozen
 class MemoryChannelStatistics:
+    """Object returned by `MemorySendChannel.statistics` and
+    `MemoryReceiveChannel.statistics`.
+
+    See :func:`open_memory_channel` for details on the fields.
+    """
+
     current_buffer_used: int
     max_buffer_size: int | float
     open_send_channels: int
@@ -152,6 +158,15 @@ def statistics(self) -> MemoryChannelStatistics:
 @final
 @attrs.define(eq=False, repr=False, slots=False)
 class MemorySendChannel(SendChannel[SendType], metaclass=NoPublicConstructor):
+    """The sending end of a memory channel.
+
+    Created by `open_memory_channel`. This implements the
+    `~trio.abc.SendChannel` interface.
+
+    See `open_memory_channel` for details, and :ref:`channel-mpmc` for a
+    discussion of channel cloning.
+    """
+
     _state: MemoryChannelState[SendType]
     _closed: bool = False
     # This is just the tasks waiting on *this* object. As compared to
@@ -300,6 +315,15 @@ async def aclose(self) -> None:
 @final
 @attrs.define(eq=False, repr=False, slots=False)
 class MemoryReceiveChannel(ReceiveChannel[ReceiveType], metaclass=NoPublicConstructor):
+    """The receiving end of a memory channel.
+
+    Created by `open_memory_channel`. This implements the
+    `~trio.abc.ReceiveChannel` interface.
+
+    See `open_memory_channel` for details, and :ref:`channel-mpmc` for a
+    discussion of channel cloning.
+    """
+
     _state: MemoryChannelState[ReceiveType]
     _closed: bool = False
     _tasks: set[trio._core._run.Task] = attrs.Factory(set)

src/trio/_core/_parking_lot.py

@@ -152,6 +152,11 @@ class ParkingLot:
     # items
     _parked: OrderedDict[Task, None] = attrs.field(factory=OrderedDict, init=False)
     broken_by: list[Task] = attrs.field(factory=list, init=False)
+    """List of tasks that have broken this lot via `break_lot`.
+
+    If empty, the lot is not broken. If non-empty, any attempt to
+    `park` in this lot will raise `~trio.BrokenResourceError`.
+    """
 
     def __len__(self) -> int:
         """Returns the number of parked tasks."""

src/trio/_highlevel_socket.py

@@ -107,6 +107,7 @@ def __init__(self, socket: SocketType) -> None:
                 self.setsockopt(tsocket.IPPROTO_TCP, tsocket.TCP_NOTSENT_LOWAT, 2**14)
 
     async def send_all(self, data: bytes | bytearray | memoryview) -> None:
+        """See `trio.abc.SendStream.send_all`."""
         if self.socket.did_shutdown_SHUT_WR:
             raise trio.ClosedResourceError("can't send data after sending EOF")
         with self._send_conflict_detector:
@@ -124,13 +125,15 @@ async def send_all(self, data: bytes | bytearray | memoryview) -> None:
                         total_sent += sent
 
     async def wait_send_all_might_not_block(self) -> None:
+        """See `trio.abc.SendStream.wait_send_all_might_not_block`."""
         with self._send_conflict_detector:
             if self.socket.fileno() == -1:
                 raise trio.ClosedResourceError
             with _translate_socket_errors_to_stream_errors():
                 await self.socket.wait_writable()
 
     async def send_eof(self) -> None:
+        """See `trio.abc.HalfCloseableStream.send_eof`."""
         with self._send_conflict_detector:
             await trio.lowlevel.checkpoint()
             # On macOS, calling shutdown a second time raises ENOTCONN, but
@@ -141,6 +144,7 @@ async def send_eof(self) -> None:
                 self.socket.shutdown(tsocket.SHUT_WR)
 
     async def receive_some(self, max_bytes: int | None = None) -> bytes:
+        """See `trio.abc.ReceiveStream.receive_some`."""
         if max_bytes is None:
             max_bytes = DEFAULT_RECEIVE_SIZE
         if max_bytes < 1:
@@ -149,6 +153,7 @@ async def receive_some(self, max_bytes: int | None = None) -> bytes:
             return await self.socket.recv(max_bytes)
 
     async def aclose(self) -> None:
+        """See `trio.abc.AsyncResource.aclose`."""
         self.socket.close()
         await trio.lowlevel.checkpoint()
 

src/trio/_subprocess.py

@@ -98,7 +98,9 @@ def pidfd_open(fd: int, flags: int) -> int:
 class HasFileno(Protocol):
     """Represents any file-like object that has a file descriptor."""
 
-    def fileno(self) -> int: ...
+    def fileno(self) -> int:
+        """Return the underlying file descriptor as an integer."""
+        ...
 
 
 @final