Automatically ignore files in .gitignore

[jdufresne]

I think a feature to automatically ignore files and directories listed in .gitignore would be useful. This file normally contains a long list of auto-generated files or files that are otherwise unnecessary to format. By pruning these big directories, black will run much faster. By adding such a feature, black will require even less configuration as most projects will no longer require passing --exclude on the command line.

Other opinionated code format tools already do this or are discussing this. For example:

JavaScript Standard: https://standardjs.com/#how-do-i-ignore-files

Paths in a project's root .gitignore file are also automatically ignored.

PHP-CS-Fixer: PHP-CS-Fixer/PHP-CS-Fixer#3947 (comment)

I think it can be fixed in a broader, generalised way, by parsing (and excluding the results of) ignore files like .gitignore.

[zsol]

I think this is reasonable for black to do :)

[behnam]

See also #541.

[jgirardet]

I'll go for it.

[jgirardet]

What should be the expected behavior between DEFAULT_EXCLUDES, command-line, pyproject and .gitignore ?
Should we just merge them or should the use of one ignore the others ?

Actually : command-line > pyproject > default. each is exclusive.

.gitignore being everywhere I don't know if we can be as exclusive.

My proposal when .igitignore exists:

• a non empty .gitignore replaces default. I'm not sure for this one.
• command line overrides all(pyproject, default, gitignore) : so it would stay as it is now.
• .gitignore + pyproject should be merged ignoring default. some directory could be versionned without needing being blakened

thanks for your opinion on it.

[jgirardet]

I need your opinion to go on @zsol

[Natim]

This is the kind of errors I'd like to get rid of:

error: cannot format kinto/plugins/admin/node_modules/react-breadcrumbs/demo/node_modules/node-forge/tests/server.py: cannot use --safe with this file; failed to parse source file with Python 3.6's builtin AST. Re-run with --fast or stop using deprecated Python 2 syntax. AST error message: invalid syntax (<unknown>, line 74)
error: cannot format kinto/plugins/admin/node_modules/react-breadcrumbs/demo/node_modules/node-forge/tests/forge_ssl/forge/ssl.py: cannot use --safe with this file; failed to parse source file with Python 3.6's builtin AST. Re-run with --fast or stop using deprecated Python 2 syntax. AST error message: invalid syntax (<unknown>, line 125)

I have no intention of formatting a node_modules folder, also one could argue that this folder has nothing to do in my code tree, but apparently for some reason it does...

Note that --exclude "/node_modules/" will do for now

[zsol]

Because we have --include, I think the most sensible option is to merge gitignore with the value of --exclude; if there's no --exclude, merge it with the default. Values in pyproject.toml basically replace the default value for command line options.

[xmo-odoo]

FWIW, on top of automatically parsing .gitignore & .hgignore (and possibly some others) several code-searching tool have standardised on a .ignore file with similar semantics, so support for that would also be nice.

[ambv]

This was solved with #878.