Fixed feed_data after feed_eof assertion errors on asyncio (#752)

Fixes #490.

docs/versionhistory.rst

@@ -29,6 +29,9 @@ This library adheres to `Semantic Versioning 2.0 <http://semver.org/>`_.
 - Fixed ``to_process.run_sync()`` failing to initialize if ``__main__.__file__`` pointed
  to a file in a nonexistent directory
  (`#696 <https://github.com/agronholm/anyio/issues/696>`_)
+- Fixed ``AssertionError: feed_data after feed_eof`` on asyncio when a subprocess is
+ closed early, before its output has been read
+ (`#490 <https://github.com/agronholm/anyio/issues/490>`_)
 - Fixed ``TaskInfo.has_pending_cancellation()`` on asyncio not respecting shielded
  scopes (`#771 <https://github.com/agronholm/anyio/issues/771>`_; PR by @gschaffner)
 - Fixed ``SocketStream.receive()`` returning ``bytearray`` instead of ``bytes`` when

src/anyio/_backends/_asyncio.py

@@ -930,7 +930,7 @@ async def receive(self, max_bytes: int = 65536) -> bytes:
  raise EndOfStream
 
  async def aclose(self) -> None:
- self._stream.feed_eof()
+ self._stream.set_exception(ClosedResourceError())
  await AsyncIOBackend.checkpoint()
 
 

tests/test_subprocesses.py

@@ -13,7 +13,13 @@
 import pytest
 from pytest import FixtureRequest
 
-from anyio import CancelScope, ClosedResourceError, open_process, run_process
+from anyio import (
+ CancelScope,
+ ClosedResourceError,
+ create_task_group,
+ open_process,
+ run_process,
+)
 from anyio.streams.buffered import BufferedByteReceiveStream
 
 pytestmark = pytest.mark.anyio
@@ -289,3 +295,33 @@ async def test_py39_arguments(
  pytest.skip(f"the {argname!r} argument is not supported by uvloop yet")
 
  raise
+
+
+async def test_close_early() -> None:
+ """Regression test for #490."""
+ code = dedent("""\
+ import sys
+ for _ in range(100):
+ sys.stdout.buffer.write(bytes(range(256)))
+ """)
+
+ async with await open_process([sys.executable, "-c", code]):
+ pass
+
+
+async def test_close_while_reading() -> None:
+ code = dedent("""\
+ import time
+
+ time.sleep(3)
+ """)
+
+ async with await open_process(
+ [sys.executable, "-c", code]
+ ) as process, create_task_group() as tg:
+ assert process.stdout
+ tg.start_soon(process.stdout.aclose)
+ with pytest.raises(ClosedResourceError):
+ await process.stdout.receive()
+
+ process.terminate()