Add Process.stdio as a convenience StapledStream of stdin and stdout

newsfragments/862.feature.rst

@@ -0,0 +1,4 @@
+Add :attr:`trio.Process.stdio`, which is a :class:`~trio.StapledStream` of
+:attr:`~trio.Process.stdin` and :attr:`~trio.Process.stdout` if both of those
+are available, and ``None`` otherwise. This is intended to make it more
+ergonomic to speak a back-and-forth protocol with a subprocess.

trio/_subprocess.py

@@ -6,8 +6,8 @@
 
 from . import _core
 from ._abc import AsyncResource
-from ._sync import CapacityLimiter, Lock
-from ._threads import run_sync_in_worker_thread
+from ._highlevel_generic import StapledStream
+from ._sync import Lock
 from ._subprocess_platform import (
     wait_child_exiting, create_pipe_to_child_stdin,
     create_pipe_from_child_output
@@ -91,6 +91,10 @@ class Process(AsyncResource):
           standard error, the written bytes become available for you
           to read here. Only available if the :class:`Process` was
           constructed using ``stderr=PIPE``; otherwise this will be None.
+      stdio (trio.StapledStream or None): A stream that sends data to
+          the child's standard input and receives from the child's standard
+          output. Only available if both :attr:`stdin` and :attr:`stdout` are
+          available; otherwise this will be None.
 
     """
 
@@ -152,6 +156,11 @@ def __init__(
             if self.stderr is not None:
                 os.close(stderr)
 
+        if self.stdin is not None and self.stdout is not None:
+            self.stdio = StapledStream(self.stdin, self.stdout)
+        else:
+            self.stdio = None
+
         self.args = self._proc.args
         self.pid = self._proc.pid
 

trio/tests/test_subprocess.py

@@ -175,12 +175,12 @@ async def test_stderr_stdout():
     ) as proc:
         assert proc.stdout is not None
         assert proc.stderr is None
-        await proc.stdin.send_all(b"1234")
-        await proc.stdin.aclose()
+        await proc.stdio.send_all(b"1234")
+        await proc.stdio.send_eof()
 
         output = []
         while True:
-            chunk = await proc.stdout.receive_some(16)
+            chunk = await proc.stdio.receive_some(16)
             if chunk == b"":
                 break
             output.append(chunk)
@@ -208,6 +208,7 @@ async def test_stderr_stdout():
                 stderr=subprocess.STDOUT,
             ) as proc:
                 os.close(w)
+                assert proc.stdio is None
                 assert proc.stdout is None
                 assert proc.stderr is None
                 await proc.stdin.send_all(b"1234")