My python project that requires a plugin that I also wrote fails on poetry install because the required plugin "doesn't match any versions"

[ileslie]

I did ask this earlier on Stackoverflow but no one has commented or answered and I have more information now (maybe).
I am using the following versions:

Poetry (version 2.1.1)
Python 3.13.2
pip 25.0.1 from <correct path to the pip location in venv>

I have written an application plugin for poetry. That project has a section in the pyproject.toml file like this:

[project]
name = "mycoolplugin"
version = "1.0.2"
...
[tool.poetry.plugins."poetry.application.plugin"]
mycoolplugin = "mycoolplugin:CoolPlugin"

It builds and creates the expected wheel. I can run and test its commands in that project and during tests run by pytest.

In the project that I want to use the plugin the pyproject.toml file contains:

[tool.poetry.requires-plugins]
mycoolplugin = ">=1.0.2"

I have now published the plugin to the company pypi site.

However poetry install still does this:

poetry install
Removing the project's plugin cache because it is outdated
Ensuring that the Poetry plugins required by the project are available...
The following Poetry plugins are required by the project but are not installed in Poetry's environment:
  - mycoolwplugin (>=1.0.2)
Installing Poetry plugins only for the current project...
Updating dependencies
Resolving dependencies...

Because poetry-project-instance depends on mycoolplugin (>=1.0.2) which doesn't match any versions, version solving failed.

I read https://github.com/orgs/python-poetry/discussions/9469 which shows that the resolver is super sensitive to the version of python in ways I also would not have expected. It seems the error message misses what is really happening and sure enough my plugin project has:

[project]
requires-python = ">=3.13,<3.14"

While my project that would like to use the plugin had

[tool.poetry.dependencies]
python = "3.13.2"

so I changed it to

[tool.poetry.dependencies]
python = ">=3.13,<3.14"

So that it matched but that gave the exact same error.

Additional notes:

1. yes I changed the name of the plugin since the company I work for will not allow even names to leak out.
2. Both projects pull dependencies form an internal pypi mirror specified thusly:

[[tool.poetry.source]]
name = "company-pypi"
url = "https://artifactory.company.com/api/pypi/pypi.python.org/simple"
priority = "primary"

What is going on? Why doesn't poetry find the plugin when the versions match? Is it really complaining about version mismatch or is it really unable to find it? What can I do to fix this?

[ileslie]

Oh this is interesting - now I'm more confused.

I ran `poetry install -vv' and see some things I expect:

Using virtualenv: /localdisk/users/me/src/company/project/build/venv/project-JtRap8DU-py3.13
...
   1: conflict: no versions of mycoolplugin match >=1.0.2
   1: ! mycoolplugin (>=1.0.2) is satisfied by mycoolplugin (>=1.0.2)
   1: ! which is caused by "poetry-project-instance depends on mycoolplugin (>=1.0.2)"
   1: ! thus: version solving failed
   1: Version solving took 1.760 seconds.
   1: Tried 1 solutions.

  Stack trace:

  4  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/puzzle/solver.py:168 in _solve
       result = resolve_version(self._package, self._provider)

  3  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/mixology/__init__.py:18 in resolve_version
       return solver.solve()

  2  /nfs/projects/thw/poetry/2.1.1/lib/python3.10/site-packages/poetry/mixology/version_solver.py:173 in solve
       self._propagate(next)

  1  /nfs/projects/thw/poetry/2.1.1/lib/python3.10/site-packages/poetry/mixology/version_solver.py:212 in _propagate
       root_cause = self._resolve_conflict(incompatibility)

  SolveFailureError

  Because poetry-project-instance depends on mycoolplugin (>=1.0.2) which doesn't match any versions, version solving failed.

  at /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/mixology/version_solver.py:433 in _resolve_conflict
      429│             )
      430│             self._log(f'! which is caused by "{most_recent_satisfier.cause}"')
      431│             self._log(f"! thus: {incompatibility}")
      432│ 
    → 433│         raise SolveFailureError(incompatibility)
      434│ 
      435│     def _choose_next(self, unsatisfied: list[Dependency]) -> Dependency:
      436│         """
      437│         The original algorithm proposes to prefer packages with as few remaining

The following error occurred when trying to handle this error:


  Stack trace:

  15  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/cleo/application.py:327 in run
        exit_code = self._run(io)

  14  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/console/application.py:260 in _run
        exit_code = super()._run(io)

  13  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/cleo/application.py:431 in _run
        exit_code = self._run_command(command, io)

  12  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/cleo/application.py:473 in _run_command
        raise error

  11  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/cleo/application.py:457 in _run_command
        exit_code = command.run(io)

  10  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/cleo/commands/base_command.py:117 in run
        return self.execute(io) or 0

   9  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/console/commands/installer_command.py:39 in execute
        return super().execute(io)

   8  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/cleo/commands/command.py:61 in execute
        return self.handle()

   7  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/console/commands/install.py:114 in handle
        PluginManager.ensure_project_plugins(self.poetry, self.io)

   6  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/plugins/plugin_manager.py:69 in ensure_project_plugins
        ProjectPluginCache(poetry, io).ensure_plugins()

   5  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/plugins/plugin_manager.py:247 in ensure_plugins
        self._install(missing_plugins, poetry_env, installed_packages)

   4  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/plugins/plugin_manager.py:293 in _install
        if installer.run() != 0:

   3  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/installation/installer.py:103 in run
        return self._do_install()

   2  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/installation/installer.py:241 in _do_install
        solved_packages = solver.solve(

   1  /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/puzzle/solver.py:87 in solve
        packages = self._solve()

  SolverProblemError

  Because poetry-project-instance depends on mycoolplugin (>=1.0.2) which doesn't match any versions, version solving failed.

  at /nfs/projects/tools/poetry/2.1.1/lib/python3.10/site-packages/poetry/puzzle/solver.py:174 in _solve
      170│             packages = result.packages
      171│         except OverrideNeededError as e:
      172│             return self._solve_in_compatibility_mode(e.overrides)
      173│         except SolveFailureError as e:
    → 174│             raise SolverProblemError(e)
      175│ 
      176│         return self._aggregate_solved_packages(packages)
      177│ 
      178│     def _aggregate_solved_packages(

That is the expected vm that I setup and created.

But

What is it using python 3.10 for? That is not the version of python I have in my venv. It is the version of python that is installed on our nfs under poetry 2.1.1 but I specifically created a venv that includes the versions of poetry and python that we want to use on this project.

poetry env info

Virtualenv
Python:         3.13.2
Implementation: CPython
Path:           /localdisk/users/me/src/company/project/build/venv/project-JtRap8DU-py3.13
Executable:     /localdisk/users/me/src/company/project/build/venv/project-JtRap8DU-py3.13/bin/python
Valid:          True

Base
Platform:   linux
OS:         posix
Python:     3.13.2
Path:       /nfs/tools/otherdir/python/3.13.2
Executable: /nfs/tools/otherdir/python/3.13.2/bin/python3.13

[ileslie]

Just had a suggestion (from AI) that I try poetry search mycoolplugin. That showed

poetry search mycoolplugin
No matching packages were found.

Sounds like I should be looking at my pypi repo setup...

[ileslie]

Solved. I added the needed pypi repo. We have a company clone of pypi with approved libraries but also my team has its own where we place things we produce. That's where my plugin resides so my project needed to reference that repo too. Fair enough.