In a poetry plugin command handler, my calls to the run command are failing but same call from the command line works fine

[ileslie]

I am creating a plugin for poetry meant to help implement our workflow. In my custom command handler I need to call several poetry commands.

The call to the poetry check command works fine:

def handle(self) -> int:
    ...
    # call poetry command check
    self.call("check", "--lock")
    ...
    self.call("run", "pytest --junit-xml=\"/path_to_location_for_test_reports/all_tests.xml\"")

However the call the to the poetry run command does not.
It fails with:

Running unit tests...
pytest --junit-xml="/path_to_location_for_test_reports/all_tests.xml"

The option "--junit-xml" does not exist

Looking at the code it seems like the processing in the call validates the arguments as parameters to the poetry run command which of course does not have one named --junit-xml. However that is not an argument for the poetry run command it is an argument for the pytest command.

I can run this on the command line:

poetry run pytest --junit-xml="/path_to_location_for_test_reports/all_tests.xml"
==================================== test session starts ========================================
platform linux -- Python 3.13.2, pytest-8.3.5, pluggy-1.5.0
rootdir: /project_root
configfile: pyproject.toml
plugins: anyio-4.9.0
collected 0 items                                                                                                                                

----------------- generated xml file: /path_to_location_for_test_reports/all_tests.xml ------------------
===================================== no tests ran in 0.01s ======================================

Yes, I have no tests in the sample project. No, having a test doesn't change anything - other than they run when I type the command on the command line.

[SirHegel]

Command.call() does not take the path that makes poetry run pytest --junit-xml=... work from the shell, so the two are not equivalent.

On the command line, Application._configure_run_command reorders the argv tokens and inserts -- after run, so everything from the subcommand on is passed through untouched. call() instead builds a StringInput from your string and runs the command directly; that input is bound against the command's merged definition (the application's command argument first, then run's args), so --junit-xml is parsed as an option of run and rejected. Reproduced with Poetry 2.4.3 / cleo 2.1.0:

• self.call("run", "pytest --junit-xml=x.xml") → The option "--junit-xml" does not exist
• self.call("run", "-- pytest --junit-xml=x.xml") → parses, but pytest is consumed by the command argument and run receives args == ["--junit-xml=x.xml"] → Command not found: --junit-xml=x.xml
• self.call("run", "run -- pytest --junit-xml=x.xml") → args == ["pytest", "--junit-xml=x.xml"], pytest runs

So with call the string has to carry the command name and the -- separator. There is a second problem with that route: on POSIX RunCommand.handle ends in Env.execute, which is os.execvpe. The Poetry process is replaced by pytest and nothing after that line in your handler runs (check --lock came back to you only because it does not exec anything).

For a handler that has to continue after the tests, use the environment directly; EnvCommand gives you self.env:

from poetry.utils.env import EnvCommandError

try:
    self.env.run("pytest", f"--junit-xml={report_path}", call=True)
except EnvCommandError as e:
    self.line_error(str(e))
    return 1

Env.run(..., call=True) is subprocess.check_call inside the project environment and returns to your code; a non-zero exit (for pytest that includes exit code 5, "no tests collected") is raised as EnvCommandError. Without call=True the output is captured and returned as a string instead. self.env is the project's virtualenv, so this runs the same pytest as poetry run pytest.

References:

• cleo Command.call: https://github.com/python-poetry/cleo/blob/2.1.0/src/cleo/commands/command.py#L71-L80
• Application._configure_run_command: https://github.com/python-poetry/poetry/blob/2.4.3/src/poetry/console/application.py#L416
• RunCommand.handle → Env.execute: https://github.com/python-poetry/poetry/blob/2.4.3/src/poetry/console/commands/run.py#L25-L34
• Env.run / Env._run / Env.execute: https://github.com/python-poetry/poetry/blob/2.4.3/src/poetry/utils/env/base_env.py#L407-L467