Poetry install no longer removes dev dependencies

• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: MacOS
• Poetry version: 0.12.2

Issue

There is currently no way to go from a develop poetry install to one that has --no-dev.

In previous versions, if you ran poetry install --no-dev it would remove all dev dependencies from the current virtual environment.

[goosemo]

This behavior seems like a bug, especially in how --no-dev is documented.

–no-dev: Do not install dev dependencies

This doesn’t state that poetry will uninstall anything. Can this be addressed with docs and perhaps a flag or configuration to not have this behavior happen?

My use case for example is to not have poetry uninstall every python package I have installed inside a docker container, or a developer machine, when it is configured to not use virtualenvs.

[owais]

This is quite a big pain point actually. It’d be nice to at least have a flag to turn this behavior off. Here is how I’m trying using it.

I’m working on a library say LibA and I need to manually test it in multiple apps during development. From docs and poetry install --help, it seems poetry install --no-dev is the exactly what I need because of:

  --no-dev               Do not install the development dependencies.

Intuitively, I felt I’d do the following:

# currently in my poetry managed LibA project
> pwd
~/LibA

# activate my test app's venv
. ~/app/venv/bin/activate

# install LibA as an editable package in app's env
poetry install --no-dev

This installs LibA as an editable install in app’s venv. Now I should be able to run the app, make changes to LibA and have them reflect in the app without having to re-install LibA after every change.

However, this doesn’t work exactly as expected. When poetry install is executed with the --no-dev option, it looks up for all dev dependencies of LibA and uninstalls them from app’s env. This is a huge issue if app has any packages in common with LibA’s dev dependencies. What makes it even worse is that poetry removes even indirect dependencies which makes it very likely for the deps to match.

I feel the default behavior should be to not install dev dependencies when --no-dev is passed (as it is documented) and to not remove any packages at all. If that is not desirable for some reason, we should be able to pass in another CLI param that prevents poetry from removing packages. Something like poetry install --no-dev --no-remove.

BTW what use cases demand that dev packages get removed when --no-dev is passed? Poetry already spports a --remove-untracked option. May be if a user wants to remove dev deps, they can run poetry install --no-dev --remove-untracked and this would ensure any dev deps are uninstalled. poetry install --no-dev would only install packages and never remove anything.

Question: Is there another ideal way to work with the workflow that I described above when using poetry?