revert reraising exceptiongroup as a TrioInternalError, mention that it may raise exceptiongroup in docstring

Author: jakkdl

src/trio/_subprocess.py

@@ -12,7 +12,7 @@
 import trio
 
 from ._abc import AsyncResource, ReceiveStream, SendStream
-from ._core import Cancelled, ClosedResourceError, TaskStatus, TrioInternalError
+from ._core import ClosedResourceError, TaskStatus
 from ._deprecate import deprecated
 from ._highlevel_generic import StapledStream
 from ._subprocess_platform import (
@@ -30,9 +30,6 @@
 
     from typing_extensions import Self, TypeAlias
 
-if sys.version_info < (3, 11):
-    from exceptiongroup import BaseExceptionGroup
-
 
 # Sphinx cannot parse the stringified version
 if sys.version_info >= (3, 9):
@@ -690,6 +687,7 @@ async def my_deliver_cancel(process):
           and the process exits with a nonzero exit status
       OSError: if an error is encountered starting or communicating with
           the process
+      ExceptionGroup: if exceptions occur in `deliver_cancel`, or when exceptions occur when communicating with the subprocess. If strict_exception_groups is set to false in the global context, then single exceptions will be collapsed.
 
     .. note:: The child process runs in the same process group as the parent
        Trio process, so a Ctrl+C will be delivered simultaneously to both
@@ -767,41 +765,36 @@ async def read_output(
     # so any exceptions get directly seen by users.
     # options needs a complex TypedDict. The overload error only occurs on Unix.
     proc = await open_process(command, **options)  # type: ignore[arg-type, call-overload, unused-ignore]
-    try:
-        async with trio.open_nursery() as nursery:
-            try:
-                if input is not None:
-                    assert proc.stdin is not None
-                    nursery.start_soon(feed_input, proc.stdin)
-                    proc.stdin = None
-                    proc.stdio = None
-                if capture_stdout:
-                    assert proc.stdout is not None
-                    nursery.start_soon(read_output, proc.stdout, stdout_chunks)
-                    proc.stdout = None
-                    proc.stdio = None
-                if capture_stderr:
-                    assert proc.stderr is not None
-                    nursery.start_soon(read_output, proc.stderr, stderr_chunks)
-                    proc.stderr = None
-                task_status.started(proc)
+    async with trio.open_nursery() as nursery:
+        try:
+            if input is not None:
+                assert proc.stdin is not None
+                nursery.start_soon(feed_input, proc.stdin)
+                proc.stdin = None
+                proc.stdio = None
+            if capture_stdout:
+                assert proc.stdout is not None
+                nursery.start_soon(read_output, proc.stdout, stdout_chunks)
+                proc.stdout = None
+                proc.stdio = None
+            if capture_stderr:
+                assert proc.stderr is not None
+                nursery.start_soon(read_output, proc.stderr, stderr_chunks)
+                proc.stderr = None
+            task_status.started(proc)
+            await proc.wait()
+        except BaseException:
+            with trio.CancelScope(shield=True):
+                killer_cscope = trio.CancelScope(shield=True)
+
+                async def killer() -> None:
+                    with killer_cscope:
+                        await deliver_cancel(proc)
+
+                nursery.start_soon(killer)
                 await proc.wait()
-            except BaseException:
-                with trio.CancelScope(shield=True):
-                    killer_cscope = trio.CancelScope(shield=True)
-
-                    async def killer() -> None:
-                        with killer_cscope:
-                            await deliver_cancel(proc)
-
-                    nursery.start_soon(killer)
-                    await proc.wait()
-                    killer_cscope.cancel()
-                    raise
-    except BaseExceptionGroup as exc:
-        if all(isinstance(e, Cancelled) for e in exc.exceptions):
-            raise exc
-        raise TrioInternalError("Error interacting with opened process") from exc
+                killer_cscope.cancel()
+                raise
 
     stdout = b"".join(stdout_chunks) if capture_stdout else None
     stderr = b"".join(stderr_chunks) if capture_stderr else None