use exact black version pre-commit uses

[RonnyPfannschmidt]

people combining pre-commit and black tend to pin the black version to control transition and formatting,
as black enhances it sometimes introduces better formatting that will conflict with a projects pinned setup

in order to avoid this dissonance it would be really useful to either use black from pre-commit if available or to take the same version

[jgirardet]

I've never used precommit so I do not really understand.
Please tell what you mean with "use black from precommit."

[RonnyPfannschmidt]

https://github.com/pytest-dev/pytest/blob/5e7d427df1b258b5e4c0f5e1496f0f68545ad4b1/.pre-commit-config.yaml#L4

is an example of the usage - we use it to ensure all commits are up to standard, now if the black the editor uses and the black the commit checking uses differ in version, there is the possibility of different outcomes (as black enhances)

[jgirardet]

if I get you, you'd like to run pre-commit run black command instead of black if black in the .pre-commit-config.yaml file ?
What about the config options (line-length, py36...) ? precommit will look in pyproject ? should we ignore sublack options if using precommit ?

[RonnyPfannschmidt]

@jgirardet i believe the black options should always be taken from black or pre-commit if feasible, its bit of - idealls sublack has no own options and defers everything to the project/its tooling, else developer preference differences will cause havoc

[jgirardet]

Hi @RonnyPfannschmidt
I discovered pre-commit and thought a bit about it.
Running black via hook on saved file is easy to do but really slows the process.
Black doesn't care much about speed (and does not need) but for sublack it's more a point since you don't want to be waiting in front of your screen waiting for formatting while coding.
a 300 lines file :

jimmy@x-or:~/trash/sublack/tests$ time black test_sublack.py 
reformatted test_sublack.py
All done! ✨ 🍰 ✨
1 file reformatted.

real	0m0,677s
user	0m0,661s
sys	0m0,022s
jimmy@x-or:~/trash/sublack/tests$ time pre-commit run black --files test_sublack.py 
black....................................................................Failed
hookid: black

Files were modified by this hook. Additional output:

reformatted tests/test_sublack.py
All done! ✨ 🍰 ✨
1 file reformatted.

real	0m1,132s
user	0m1,067s
sys	0m0,070s

So i'm not sure about running sublack via precommit by defaut if black's hook is present.

The other matter comes with unsaved file : since I use black - to format via stdin/stdout I can't use it with pre-commit because pre-commit does not accept additional arguments to hook in the command line(or I missed it)
so 2 ways:

• format via a tempfile,
• or always save file before applying black wen using pre-commit.
  These 2 ways will probably also slow the process and force more disk access.

Last thing, black_on_save would also force to save the file twice to format.

Please tell if I'm wrong or if you think to another/better implementation.

[RonnyPfannschmidt]

@jgirardet that's indeed a unfortunate setup - i will open a accompanying issue for pre-commit as its definitively a useful item

[jgirardet]

Hi @RonnyPfannschmidt ,
After talking with asotille, for now I'm ok to add it but as an optional behavior.
I'll keep you in touch

[jgirardet]

It's on master. you have to use the option "black_use_precommit"

[jgirardet]

in v 2.1.0