define Yapf config

[Borda]

What does this PR do?

eventually, we would move to Yet-Another-Python-Formater so this is just setting rules, for illustration how it goes you can check Bolts codebase when we have already deployed it
With deploy YAPF check we may drop ISORT which has atm incompatibility with PEP8, see PyCQA/isort#1594 (comment)
discussed with @tchaton and finetuned config with @akihironitta

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[codecov]

Codecov Report

Merging #5591 (6820889) into release/1.2-dev (3da28fd) will decrease coverage by 0%.
The diff coverage is n/a.

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- Coverage               89%     89%    -0%     
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- Hits                 11103   10933   -170     
- Misses                1320    1334    +14     

[carmocca]

So why yapf over alternatives? (black, for example: https://news.ycombinator.com/item?id=17155048)

[Borda]

So why yapf over alternatives? (black, for example: https://news.ycombinator.com/item?id=17155048)

We have already spoke about it, black is just one (no way to configure as far as I know) so you either like it or hate it...
On the other hand with yapf you have some freedom to set it up...

Btw, not sure how much it still relevant comment from 2018 (2 years ago)
And my experience is that black is less deterministic and much longer which makes it more difficult to read...

@carmocca have you check how Bolts looks like now?

EDIT: in fact there are not so many alternatives, see Lightning-Universe/lightning-bolts#482

[carmocca]

And my experience is that black is less deterministic and much longer which makes it more difficult to read...

Never used yapf but reading online, seems like its the other way around.

What I care about the most is that the formatter only allows one consistent single style. If yapf does, then that's OK with me

[Borda]

What I care about the most is that the formatter only allows one consistent single style. If yapf does, then that's OK with me

So far I have tested, with one setting it does, but if you want we can test it a bit longer with Bolts first...

[awaelchli]

the drawback is that if you change your mind about the config, you have to reformat the whole code base.
I have one wish, I beg you, please if it's possible can we avoid this code style:

foo_long_function_(arg1, arg2, arg3
                   arg4, arg5, arg6)

it leads to uneven indentation which is just horrible in my opinion.

[Borda]

I have one wish, I beg you, please if it's possible can we avoid this code style:

foo_long_function_(arg1, arg2, arg3
                   arg4, arg5, arg6)

Heh, that you are lucky guy, I hate it too =D

[tchaton]

Love it ! Great addition !

[tchaton]

Great addition !

[akihironitta]

In Bolts, I had a collision between flake8 and yapf. Applying yapf caused the error [W503] line break before binary operator from flake8, so shall we modify the flake8 config to ignore W503? https://github.com/PyTorchLightning/pytorch-lightning-bolts/pull/462/files#r561509665

[Borda]

In Bolts, I had a collision between flake8 and yapf. Applying yapf caused the error [W503] line break before binary operator from flake8, so shall we modify the flake8 config to ignore W503? https://github.com/PyTorchLightning/pytorch-lightning-bolts/pull/462/files#r561509665

we can configure this in yapf, right?

[akihironitta]

@Borda Could you have a look at Lightning-Universe/lightning-bolts#539? I'm having difficulty in resolving the conflicts between pep8 (flake8) and yapf. It seems that yapf is not really compliant with pep8 even if we set:

[yapf]
based_on_style = pep8

[akihironitta]

In Bolts, we had conflicts between yapf and flake8, and @Borda resolved errors from flake8 by writing those lines in a different way. Lightning-Universe/lightning-bolts#539 So, here, I don't think we need to modify our flake8 config for now.

[Borda]

I still think that you shall write reasonable code, and there are always multiple ways... :]