`pytest --collect-only --quiet` output is not "machine readable"

What’s the problem this feature will solve?

I would like to programmatically collect the list of test ids from pytest.

current pytest --collect-only --quiet gets close, but has some non-machine-readable output at the end which is not desirable.

$ pytest --collect-only --quiet tests | tail -5
tests/astpretty_test.py::test_typedast_support_cmdline_27
tests/astpretty_test.py::test_typedast_support_cmdline_3
tests/astpretty_test.py::test_pformat_py38_type_comments

28 tests collected in 0.02s

Describe the solution you’d like

I would like to add either a --json output to this so it can be machine-parsed. perhaps a structure like:

$ pytest --collect-only --json
{
    "testids": [
        "...",
        "...",
        "..."
    ]
}

Alternative Solutions

I could write a plugin, but…

Additional context

I’m writing a tool to detect test pollution automatically. also I suspect this would be useful for those attempting to distribute tests by id across runners – for instance pytest-select

[asottile]

@elbehery95 head -2 and strip are both hacks indicating that there is not structured output which is entirely what this issue is asking for – you’ll note that the original issue shows exactly the command you’re using and doesn’t help

adding a plugin of course makes this possible but the ask is for pytest to do this itself

[elbehery95]

I would like to programmatically collect the list of test ids from pytest.

I believe there are many ways to do this E.g.

Shell approach:

pytest --collect-only -q tests/test_hello.py | head -n -2 | python -c 'import sys; tests=[i.strip() for i in sys.stdin.readlines()]; print(tests)'

Python approach:

import pytest

class MyCollectionPlugin:
  def __init__(self):
    self.tests = []
  def pytest_report_collectionfinish(self, items):
    self.tests = [item.nodeid for item in items]


if __name__ == "__main__":
  p = MyCollectionPlugin()
  pytest.main(["--collect-only"], plugins=[p])
  print(p.tests)
  # generate_json_from_items_nodeid_list(p.tests)