Partial fix: Callable alias can provoke Bad file descriptor exception in the internal or external code (#5645)

* fix

* fix

* test

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* news

* test

* test

* test

* test

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* news

* bump test

* bump test

* test

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* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: a <1@1.1>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

news/fix_bad_file_descriptor.rst

@@ -0,0 +1,23 @@
+**Added:**
+
+* <news item>
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* Partial fix for "Bad file descriptor" in case of callable alias with execx invocation inside e.g. ExecAlias (#5645).
+
+**Security:**
+
+* <news item>

tests/test_integrations.py

@@ -1508,3 +1508,41 @@ def test_shebang_cr(tmpdir):
     command = f"cd {testdir}; ./{testfile}\n"
     out, err, rtn = run_xonsh(command)
     assert out == f"{expected_out}\n"
+
+
+test_code = [
+    """
+$XONSH_SHOW_TRACEBACK = True
+@aliases.register
+def _e(a,i,o,e):
+    echo -n O
+    echo -n E 1>2
+    execx("echo -n O")
+    execx("echo -n E 1>2")
+    print("o")
+    print("O", file=o)
+    print("E", file=e)
+
+import tempfile
+for i in range(0, 12):
+    echo -n e
+    print($(e), !(e), $[e], ![e])
+    print($(e > @(tempfile.NamedTemporaryFile(delete=False).name)))
+    print(!(e > @(tempfile.NamedTemporaryFile(delete=False).name)))
+    print($[e > @(tempfile.NamedTemporaryFile(delete=False).name)])
+    print(![e > @(tempfile.NamedTemporaryFile(delete=False).name)])
+"""
+]
+
+
+@skip_if_on_windows
+@pytest.mark.parametrize("test_code", test_code)
+def test_callable_alias_no_bad_file_descriptor(test_code):
+    """Test no exceptions during any kind of capturing of callable alias. See also #5631."""
+
+    out, err, ret = run_xonsh(
+        test_code, interactive=True, single_command=True, timeout=60
+    )
+    assert ret == 0
+    assert "Error" not in out
+    assert "Exception" not in out

xonsh/procs/proxies.py

@@ -511,7 +511,10 @@ class ProcProxyThread(threading.Thread):
         # clean up
         # scopz: not sure why this is needed, but stdin cannot go here
         # and stdout & stderr must.
-        handles = [self.stdout, self.stderr]
+        if xp.ON_WINDOWS:
+            handles = [self.stdout, self.stderr]
+        else:
+            handles = [sp_stdout, sp_stderr]
         for handle in handles:
             safe_fdclose(handle, cache=self._closed_handle_cache)