Capturing the stderr of xonsh.lib.subprocess.run

[Matthieu-LAURENT39]

Is there a way to capture the stderr of a command run via xonsh.lib.subprocess.run?
stdout musn't be captured as it's a TUI app.
And i can't use regular subprocess.run, as i need to access the xonsh environment

[Matthieu-LAURENT39]

I tried using

f = BytesIO()
xonsh.procs.specs.SubprocSpec(['ls'], stdout=f).run()

But it failed with io.UnsupportedOperation: fileno...
I guess there's no way but to use a temp file :/

[Matthieu-LAURENT39]

I thought maybe

p = xonsh.procs.specs.SubprocSpec(['ls'], stdout=subprocess.PIPE)
p.run()
print(p.stdout)

would work, but it just prints -1...

[Matthieu-LAURENT39]

I gave up and used

with tempfile.NamedTemporaryFile(mode="w+", encoding="utf8") as f:
    ls e> @(f.name)

I'll leave the discussion open since it's not a proper fix, but if you have the same issue i had, then this is probably the way to go

[anki-code]

Try start from:

!(ls 123)
#CommandPipeline(
#  stdin=<_io.BytesIO object at 0x110b8e570>,
#  stdout=<_io.BytesIO object at 0x110b8f560>,
#  stderr=<_io.BytesIO object at 0x110b8ede0>,
#  ...
#  output='',
#  errors="ls: cannot access '123': No such file or directory\n". # <<<<<<<<<<<<<<<<<<<
# )

# And the same with
__xonsh__.subproc_captured_object(['ls', '123'])
# That calls:
# xonsh.procs.specs.run_subproc(cmds, captured="hiddenobject", envs=envs)

[Matthieu-LAURENT39]

Using !(ls) doesn't seem to capture stdoud nor stderr, unlike $(ls)
I get

!(ls)                                                                                                                         
# output of ls displayed to stdout
CommandPipeline(
  stdin=None,
  stdout=None,
  stderr=None,
  pid=1515429,
  returncode=0,
  args=['ls'],
  alias=['lsd'],
  stdin_redirect=['<stdin>', 'r'],
  stdout_redirect=['<stdout>', 'a'],
  stderr_redirect=['<stderr>', 'r'],
  timestamps=[1699612526.6892931, 1699612526.8065586],
  executed_cmd=['lsd'],
  input='',
  output='',
  errors=None
)

But that aside, even if it did capture it wouldn't work, as i need to NOT capture stdout (it's a TUI app so the interface must be displayed), but only capture stderr