Poetry removes it's own dependencies with `install --no-dev` when it manages the environment it is installed in

• I am on the latest Poetry version.

• I have searched the issues of this repo and believe that this is not a duplicate.
  Well… This issue is mentioned by @sontek in https://github.com/python-poetry/poetry/issues/3139#issuecomment-776355443_ but the response below advises to create a new issue, so here I am.

• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: Docker image based on python:3.9.1

• Poetry version: 1.1.6

• Link of a Gist with the contents of your pyproject.toml file: https://gist.github.com/gbdlin/311dda3cd34672370cd97bf07f306a61

Issue

When you specify a package in the dev-dependencies that is either a dependency of the poetry itself or it depends on one of the poetry dependencies, and you’ve installed poetry inside an environment that poetry is supposed to manage, poetry will uninstall this mentioned dependency after invoking poetry install --no-dev, making itself unusable in the future.

I’m aware that it is advised to install poetry outside of the environment it should manage, but this is very often seen inside docker images (such example provided in the gist linked above) to save on the resources.

Example output presenting mentioned issue (without -vvv ands):

$ pip install poetry
Requirement already satisfied: pip in /usr/local/lib/python3.9/site-packages (21.0.1)
Collecting poetry
  Downloading poetry-1.1.6-py2.py3-none-any.whl (172 kB)
[ ... 70 irrelevant output lines truncated ... ]
Collecting appdirs<2,>=1.4.3
  Downloading appdirs-1.4.4-py2.py3-none-any.whl (9.6 kB)
Installing collected packages: [ ... ] appdirs, [ ... ] poetry
Successfully installed [ ... ] appdirs-1.4.4 [ ... ] poetry-1.1.6 [ ... ]

$ poetry config virtualenvs.create false && poetry install --no-dev

Skipping virtualenv creation, as specified in config file.
Installing dependencies from lock file

Package operations: 0 installs, 0 updates, 1 removal

  • Removing appdirs (1.4.4)
Removing intermediate container af920367a74d

As you can see, appdirs, which is required by the poetry, was uninstalled by poetry. Full log, with the -vvv and the attempt to run poetry again, available here

[gbdlin]

If this is expected, it’s for sure not documented properly. Both in the documentation and when just using poetry install --help, the --no-dev option is described as Do not install the development dependencies., not Get rid of the development dependencies. There is also a 2nd command line options --remove-untracked, from which I would expect to remove some dependencies.

But even if the --no-dev’s expected behavior is to remove all dev dependencies, poetry should do one of those:

• do an exception for its own dependencies if it’s being run from the same virtualenv,
• don’t remove anything implicitly when it’s being run from the same virtualenv,
• provide additional command line option that allows skipping the removal of dev dependencies.

[finswimmer]

This has change with poetry 1.2.0a2: Poetry wan’t remove installed packages unless the --sync option is given.

However, if a dependency will be removed due to a version change e.g. on poetry update the package will be removed of course from the venv.

fin swimmer