'Plugin already registered' error when registering multiple plugins with setuptools

[dgard1981]

I am developing some plugins locally that I hope to one day publish, so I'm registering them using setuptools. As I'm only testing at the moment, to install them I'm using the --editable option.

pip install  --editable pytest_plugins/pytest_plugin1
pip install  --editable pytest_plugins/pytest_plugin2

If just either one of the plugins is installed, pytest works fine. In this case only pytest_plugin2 is installed.

user@computer:~$ pytest tests -q
.                                                                                                                                                                                              [100%]
Output from Plugin 2.
1 passed in 0.00s

However, if both are installed pytest fails. It looks as though both plugins are trying to read from the same path, '/home/user/pytest_plugins/pytest_plugin1/src/plugin.py.

ValueError: Plugin already registered under a different name: pytest_plugin2=<module 'src.plugin' from '/home/user/pytest_plugins/pytest_plugin1/src/plugin.py'>

I'm guessing this is somehow to do with how pip imports paths for --editable installs, but I'm not totally sure. Is this a known issue with plugins, and if so is there a workaround?

---

Example files

.
├─ pytest_plugins
│   ├─ pytest_plugin1
│   │   ├─ src
│   │   │   └─ plugin.py
│   │   └─ setup.py
│   └─ pytest_plugin2
│       ├─ src
│       │   └─ plugin.py
│       └─ setup.py
└─ tests
    └─ test_something.py

pytest_plugins/pytest_plugin1/setup.py

from setuptools import setup, find_packages

setup(
  name='pytest_plugin1',
  packages=find_packages(include=['pytest_plugin1']),
  entry_points={'pytest11': ['pytest_plugin1 = src.plugin']}
)

pytest_plugins/pytest_plugin1/src/plugin.py

import pytest

@pytest.hookimpl
def pytest_terminal_summary(*_) -> None:
  print('Output from Plugin 1.')

pytest_plugins/pytest_plugin2/setup.py

from setuptools import setup, find_packages

setup(
  name='pytest_plugin2',
  packages=find_packages(include=['pytest_plugin2']),
  entry_points={'pytest11': ['pytest_plugin2 = src.plugin']}
)

pytest_plugins/pytest_plugin2/src/plugin.py

import pytest

@pytest.hookimpl
def pytest_terminal_summary(*_) -> None:
  print('Output from Plugin 2.')

tests/test_something

def test_something():
  assert 1 == 1

[dgard1981]

Further investigation shows that this is down to how the entry point is loaded. I'm note sure if the use of --editable packages has contributed to the issue.

>>> import importlib_metadata
>>> for dist in list(importlib_metadata.distributions()):
...     for ep in dist.entry_points:
...         if ep.name.startswith('pytest_plugin'):
...             print(ep)
...             print(ep.load())
... 
EntryPoint(name='pytest_plugin1', value='src.plugin', group='pytest11')
<module 'src.plugin' from '/home/user/pytest_plugins/pytest_plugin1/src/plugin.py'>
EntryPoint(name='pytest_plugin2', value='src.plugin', group='pytest11')
<module 'src.plugin' from '/home/user/pytest_plugins/pytest_plugin1/src/plugin.py'>

[RonnyPfannschmidt]

All the plugins share the same module name ,thats bound to break,

Different packages need different module top levels

[dgard1981]

But they don't share the same package name. The only similarity is the entry point within the package.

[RonnyPfannschmidt]

Both end up as src.plugin, package name doesn't matter, top-level import name does

[dgard1981]

I was able to resolve my issue with here.