Create sharable configuration presets for isort

[sobolevn]

Problem

I am writing quite a complex flake8 plugin with lots of configuration options.
Moreover, I also depend on a lot of other plugins as dependencies. Including flake8-isort.

Here's how my configuration looks like for an end user, contents of setup.cfg:

[isort]
# See https://github.com/timothycrosley/isort#multi-line-output-modes
multi_line_output = 3
include_trailing_comma = true
default_section = FIRSTPARTY
# Is the same as 80 in flake8:
line_length = 79

I do not want my users to copy-paste these settings for several reasons:

1. They usually make mistakes in this simple action :slight_smile:
2. I am losing control over the default configuration: I will not be able to change something in their defaults even if I want to
3. It brings a lot of copy-paste. That's totally inconvenient to use and maintain. One new feature or a bug might force you to go trough all your X project and edit the configuration.

Real world use-cases

Several other linters have this feature. Some of them even consider it as a key feature.

• EsLint: https://eslint.org/docs/developer-guide/shareable-configs
• TsLint: https://palantir.github.io/tslint/2016/03/31/sharable-configurations-rules.html
• Stylelint: https://stylelint.io/user-guide/configuration
• Rubocop: https://github.com/rubocop-hq/rubocop/blob/master/manual/configuration.md#inheriting-configuration-from-a-dependency-gem

When working for EsLint for example, one can just create a module with a single javascript file and reuse it everywhere.

I propose the same for flake8.
Each user can create its own set of rules for an organisation / set of projects and reuse it without this amount of copy-paste.

Implementation details

Things to point out:

1. It is not a breaking change, everything so work as-is, no major version bump is required
2. Without new feature everything should work as-is
3. New configuration option should take the lowest priority over existing config options

Configuration priority

Higher takes the priority over lower:

1. CLI flags
2. setup.cfg / .isort.cfg
3. New option: --sharable-configuration

Creating new sharable configuration

I guess that reusing entry points here is the best option.

# setup.py
# ...

setup(
   name='my-flake8-config'
   entry_points={
        'isort.configuration': [
            'myconfig = some.path:ConfigurationClass',
        ],
    },

Then:

1. Installing: pip install my-isort-config
2. Running: isort --sharable-configuration=myconfig
3. Done!

Configuration class API

I am not sure about this. But my vision would be something like:

# some/path.py

class ConfigurationClass(object):
    def sharable_configuration(self):
        return {
           'default_section': 'FIRSTPARTY',
           # and any other options for `[isort]` section
        }

Conclusion

This feature allows to transfer configuration in a reliable and clean way, brings no breaking changes, follows the best practices of other lint tools.

Original issue from wemake-python-styleguide: wemake-services/wemake-python-styleguide#164
The same feature I proposed for flake8: https://gitlab.com/pycqa/flake8/issues/555

I am super excited to help! @timothycrosley what do you think?

[timothycrosley]

I would love to have something like this! Ideally, it would hook into the new profiles feature, simply adding a new profile when a sharable configuration was installed. @sobolevn are you still interested in working on this?

[sobolevn]

I am sorry, but I don't think that I have time for this 😞

This might also be related:

1. We use nitpick to sync the configuration between our projects: https://nitpick.readthedocs.io/en/latest/
2. Here's how we store this configuration in our styleguide repository: https://github.com/wemake-services/wemake-python-styleguide/blob/master/styles/isort.toml

[timothycrosley]

This is fixed in develop (see: https://github.com/timothycrosley/isort/tree/develop/example_shared_isort_profile) and will be released in version 5.2.0.

Thanks!

~Timothy

[timothycrosley]

This was just deployed with version 5.2.0 of isort. Thanks!

~Timothy