Clarify that poetry update only updates main dependencies

[hugobuddel]

Add a note that --with is required to let poetry update also update optional dependency groups.

This behavior of poetry update confused me, so I thought let's try to save other people the trouble by updating the documentation.

I do want to note that I find the behavior strange. If I do poetry install --with=dev followed by poetry update, then I expect all installed dependencies to be updated, also the dev ones.

Pull Request Check List

Resolves: #issue-number-here

• Added tests for changed code.
• Updated documentation for changed code.

[dimbleby]

update is a two-phase process: first locking, then installing. I think perhaps this is what the docs could be clearer about.

eg your first change is definitely wrong, the lockfile will be updated even for dependencies in optional groups

I think what has surprised you is that update has the same semantics as install during the install phase

[hugobuddel]

You are right, the lock file is indeed updated, but the optional dependencies that are installed are not updated; clarified that.

The behavior is rather confusing (to me at least), so it is good to be as explicit as possible.

[dimbleby]

I think this is pedantically not correct - non-optional dependency groups are also updated, right?

[hugobuddel]

That is probably right than non-optional dependency groups are also updated, although I have not tested this; updated, thanks.

[hugobuddel]

I was wondering whether the update behavior can leave the user with a broken state, and that seems indeed possible. E.g. see this example project https://github.com/hugobuddel/poetrytest

Maybe we should add a warning that the user can be left with an inconsistent environment if poetry update is called with different dependency groups specified than when the project was first installed?