Maintain --dev / -D for dev dependencies

[ccrvlh]

As I understand, the old way of declaring dependencies is being deprecated, favoring a more flexible approach where one could have many group of dependencies, so the new recommended approach becomes -G dev.

As much as one could have multiple varying groups of dependencies (test, typed, dev, local etc etc), probably one of the most common operations would be whether to add a project dependency (poetry add pandas) or just a development dependency poetry add mypy).

--dev / -D is arguably a very intuitive way of doing this and with less friction (when compared to dev being a group of dependencies), some package managers from other languages (yarn uses --dev / -D while npm uses --save-dev) and pipenv also has a --dev option.

As much as I understand the option for a more flexible --group approach, I would like to suggest keeping the --dev / -D as shortcut - it's a great convenience flag, a lot easier/intuitive to use, and don't really see many downsides to it.

[wxgeo]

I totally agree with previous comment.

While I use very often poetry add -D <new_lib>, I never use any other group than dev, and I expect many users to be in the same situation.

From a user point of view, much of poetry strength lies in its intuitive interface, and using -D or --dev seems both more efficient and more natural to me.

I can't see any disadvantage to keeping -D/--dev as a shortcut to --group dev.

[Askir]

I like the idea of groups but I have to admit that 90%+ of python projects that I've worked on only ever will have dev as a group so I would never have to worry about the group functionality. So +1 for keeping the convenience flags.