PytestAssertRewriteWarning when including a plugin via 'pytest_plugins' and importing

[LewisGaul]

Warning when running pytest:
PytestAssertRewriteWarning: Module already imported so cannot be rewritten: plugin

Steps to reproduce

• Create a local plugin, e.g. empty plugin.py file.
• Create a test that includes the plugin via pytest_plugins and also imports the plugin:

import plugin
pytest_plugins = ("plugin",)

• Run the tests:

$pytest test.py
=============================================== test session starts ================================================
platform linux -- Python 3.8.10, pytest-7.4.0, pluggy-1.2.0
rootdir: /home/legaul/tmp/pytest-issue
collected 0 items

================================================= warnings summary =================================================
venv/lib/python3.8/site-packages/_pytest/config/__init__.py:755
  /home/legaul/tmp/pytest-issue/venv/lib/python3.8/site-packages/_pytest/config/__init__.py:755: PytestAssertRewriteWarning: Module already imported so cannot be rewritten: plugin
    self.import_plugin(import_spec)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
================================================ 1 warning in 0.01s ================================================

Extra information

Obviously this is a contrived minimal example; a more realistic scenario is:

• conftest.py contains pytest_plugins = (...)
• Some indirect import of the plugin, e.g. for the purpose of type annotations

This is not seen when loading the plugin using pytest -p plugin instead (since the import happens earlier?).

Perhaps related to #10230?

[The-Compiler]

See the relevant docs:

Plugins imported by pytest_plugins will also automatically be marked for assertion rewriting (see pytest.register_assert_rewrite()). However for this to have any effect the module must not be imported already; if it was already imported at the time the pytest_plugins statement is processed, a warning will result and assertions inside the plugin will not be rewritten. To fix this you can either call pytest.register_assert_rewrite() yourself before the module is imported, or you can arrange the code to delay the importing until after the plugin is registered.

[DeflateAwning]

This is not working with pytest_jsonreport:

import pytest
pytest.register_assert_rewrite('pytest_jsonreport', 'JSONReport', 'json_report_plugin') # Source: https://github.com/pytest-dev/pytest/issues/11150; call before importing pytest_jsonreport
from pytest_jsonreport.plugin import JSONReport
pytest.register_assert_rewrite('pytest_jsonreport', 'JSONReport', 'json_report_plugin') # Source: https://github.com/pytest-dev/pytest/issues/11150; call before importing pytest_jsonreport

Any suggestions what I'm doing wrong? @The-Compiler

[The-Compiler]

@DeflateAwning Sorry, this got lost in my inbox. You should probably call pytest.register_assert_rewrite('pytest_jsonreport.plugin') because that's what you import.

If it's not that, make sure it really didn't get imported before, e.g. via assert "pytest_jsonreport" not in sys.modules and assert "pytest_jsonreport.plugin" not in sys.modules.

[DeflateAwning]

Weird, still didn't work