Config overrides function

[shawnbot]

This implements the proposal in #4374. TL;DR: configOverrides can be a function that takes a fully resolved config and either modifies it in place and/or returns a new one:

const anymatch = require('anymatch')
module.exports = {
  extends: ['some-other-config'],
  configOverrides: config => {
    // modify, add, or remove plugins config.rules and config.plugins
  }
}

--rules CLI option

As a demonstration of how this works, I've also implemented a fix for #4331 with a new CLI flag: --rules <comma-separated-list> adds an config override that filters the configuration's rules object to include only the named rules in the list.

I haven't added docs for this yet, but I wanted to be sure that this change was welcome before doing so. I think it's super useful and would love not to have to maintain stylelint-only. 😁

File filters?

This might pave the way for a solution to #3128, but I'm honestly not sure where in stylelint's configuration "lifecycle" the configuration is augmented, and it's entirely possible that this happens before the config is applied to individual files. If so, a follow-up would need to be necessary to either:

1. Apply configOverrides() for each file, and pass the file information to it; or
2. Use this function under the hood to implement one of the declarative file override patterns proposed in Add overrides property to configuration object #3128.

Either way, this mechanism is only available in JS configs, and won't work in JSON or YAML.

[shawnbot]

@hudochenkov I'd love your input on whether the --rules option proposed here is good to move forward before I add docs and open it up for review. ❤️

[shawnbot]

Looks like I also might need some help on resolving some of the Flow errors, too 😬

[vankop]

@shawnbot Thanks for PR, looks good! I think we need to support "smart" merge, too. (maybe in another PR) Could you please create test case with .stylelintrc file? We need to support it as well.

@hudochenkov new problem with Windows in CI =( Maybe our previous hack (with commands chaining) is unnecessary now

UPD: Oh, it is only about Node.js api =( Won't this approach work for object as well?

[vankop]

1. Apply configOverrides() for each file, and pass the file information to it

I think this is more useful

2. Use this function under the hood to implement one of the declarative file override patterns proposed in Add overrides property to configuration object #3128.

I think this is not possible in current stylelint design, we can not rely on syntax when overriding config. As I can see we can use babel approach here. Something like:

{
    ...
   overrides: {
           include: "../components",
           syntax: "css-in-js",
           ...
   }
}

So under the hood we can create overrides function and call it for each file using first approach API

[shawnbot]

@shawnbot Thanks for PR, looks good! I think we need to support "smart" merge, too. (maybe in another PR) Could you please create test case with .stylelintrc file? We need to support it as well.

Thanks, @vankop; can you point me toward where "smart" merge happens?

[vankop]

I was meaning to use mergeConfigs option https://github.com/stylelint/stylelint/blob/master/lib/augmentConfig.js#L244 , since this feature available only for Node.js API I think it will be enough to just provide this function in public API. Code usage:

const configSCSS = require('./config.scss');
const {mergeConfigs} = require('stylelint');
module.exports = {
  extends: ['some-other-config'],
  configOverrides: config => {
    config = mergeConfigs(config, configSCSS)
  }
}

[hudochenkov]

Thank you for investigating possibilities.

We should discuss configOverrides proposal in #4374 first.

Proposed new flag is not discussed yet. #4331

[shawnbot]

Closing, as we've decided to go a different direction. ✌️