Proposal to add `--dry-run` flag to `makemessages` command

[Sobolev Nikita]

Sometimes I face a little, but really annoying problem with django: quite often developers forget to add or modify translations after some code changes are made. As the result some strings end up untranslated for final users.

And it is really hard (or even impossible) to test or automate on user's end.
Current solution is to watch for this kind of things during code reviews (error-prone) and E2E manual tests (too expensive).

To solve this problem we can add --dry-run option to makemessages command to fail the build if some untranslated strings or even whole locales are found.

That's exactly how other commands behave:

• makemigrations --dry-run fails the build when any new migrations would be created
• collectstatic --dry-run ensures that everything works for the static files

But for some reason the same behaviour for makemessages is not available.
Nor I was able to find any existing 3rd party solutions.

My attempt to add custom checkmessages command was unsuccessful due to very complicated code structure and multiple required mocks of the original command.

On the other hand, it could be quite difficult to implement. Because, there are a lot of machinery and corner-cases involved.
And as I understand there's no incremental mode or --dry-run in gettext world.

Original idea from wemake-django-template: ​https://github.com/wemake-services/wemake-django-template/issues/995

Looking forward to hearing your feedback, thanks!

[Baptiste Mispelon]

I think what you're asking for is tracked as part of #26803 (if I understand correctly, your proposed --dry-run is called --exit in that other ticket).