Isort: More prominent black compatibility documentation

[timothycrosley]

There has been some confusion about how to make isort compatible with Black. As Black is quickly, and for good reason (IMHO) becoming the dominant source code formatter for Python, isort should prominently display (above the fold) how to make the two projects compatible. For most users this simply means isort --profile black. Details should include when used with pre-commit, set via a config, etc.

[Bhupesh-V]

Up for grabs?
3 things to add:

• [ ] Basic compatibility (black v/s isort)
• [ ] Integration with _pre-commit_
• [ ] Using a config file (.isort.cfg)

Anything else?

[timothycrosley]

@Bhupesh-V yep! Feel free to work on this, and I think that sounds right to me.

Thanks!

[Bhupesh-V]

@Bhupesh-V yep! Feel free to work on this, and I think that sounds right to me.

Thanks!

Ok thanks, I will come up with a draft PR soon

[ssbarnea]

I am quite curious about mixing pre-commit, black and isort as I recently encountered some problems where isort seems to make changes but only on CI.

[timothycrosley]

@ssbarnea are you able to provide additional information about this case? I'd encourage you to open a new issue for it providing:

1. The output of isort . --show-settings
2. A list of all the ways you run isort. How does it run with pre-commit? How does it run on CI/CD?
3. The version of isort

Running isort, with the same file and settings, should be guaranteed to produce the same output. However, if you use pre-commit for local, and CD runs it directly, it's very easy for an incorrect configuration or simply different configuration to be passed to one vs the other.

https://github.com/PyCQA/isort/pull/1549 is a good example of this. pre-commit doesn't offer a clean way to sort all file types that isort supports, so a lot of pre-commit setups will only sort .py and "succeed" locally, but then fail in CD when it sorts .pyi and .pyx files.

[AndreCimander]

@Bhupesh-V Many thanks for doing this :+1:

Might I recommend adding a strong hint about using --filter-files in the pre-commit hook and skip_glob in the config file? One of my clients had a frustrating experience trying to exclude certain files using the pre-commit hook and I also had to read up on it.

[timothycrosley]

@AndreCimander that's a good call out, and another area where calling via isort directly and calling via pre-commit are not identical. It may make sense for there to be a dedicated pre-commit guide as well (beyond just for black compatibility)

[timothycrosley]

@AndreCimander, curious if this happened before isort updated it's own pre-commit hook to include that by default, or if you / your client was using a pre-commit mirror instead?

[AndreCimander]

@timothycrosley I was quite recently and I only found the isort pre-commit hook in the yaml, so I would guess the latter. The main issue was the differing initial behaviour of the manually triggered CLI command and the pre-commit hook, since the hook passes the filenames which in turn overwrites the normal excludes (which, imho, is the valid behaviour, just not 100% obvious).

This created some minor acceptance-grumbling within the team against pre-commit, which ensured lengthy discussions that could have been avoided ((makes one wonder if other teams also had those discussions where the argument never change a running system prevailed))