Add support for defining default value via environment variable

[titouanmathis]

What is the problem you're trying to solve?

In a shareable GitLab CI configuration, I use the custom-formatter and cache CLI arguments to improve the performance of my code quality tests and upload reports t GitLab Code Quality Report feature.

stylelint:
  variables:
    STYLELINT_ARGS: --version
    STYLELINT_FORMATTER: node_modules/stylelint-formatter-gitlab
  script:
    - npx stylelint $STYLELINT_ARGS --custom-formatter $STYLELINT_FORMATTER --cache --cache-location .stylelintcache-$CI_NODE_INDEX

This can then be used by include the configuration, and specifying the STYLELINT_ARGS variable:

include: 
  - path/to/stylelint.yml

stylelint:
  variables:
    STYLELINT_ARGS: path/to/my/src

This implementation hide the complex configurations from the final user, but also limits them in terms of what they can do.

An ideal implementation would be to define the --custom-formatter, --cache and --cache-location as environment variables to make sure that they are correctly defined, while letting the final user use the command they need.

What solution would you like to see?

Being able to define some CLI arguments as environment variables:

# Enable cache
stylelint . --cache 
STYLELINT_CACHE=true stylelint . 

# Define a custom formatter
stylelint . --custom-formatter=node_modules/formatter/index.js
STYLELINT_CUSTOM_FORMATTER=node_modules/formatter/index.js stylelint . 

# Define a custom config
stylelint . --config=path/to/config.js
STYLELINT_CONFIG=path/to/config.js stylelint . 

I think this could be implemented directly in lib/cli.mjs by setting default values when defining the flags.

I am willing to work on this feature if this is approved.

[Mouvedia]

What you are describing requires an user-provided config file, which already supports cache.
formatter is missing from https://github.com/stylelint/stylelint/blob/main/types/stylelint/index.d.ts#L102 though.
@ybiquitous is it an oversight?
If so should it be added to #5142?

i.e. if both properties are supported only the config is necessary, if so --config would be sufficient IMO

[ybiquitous]

@titouanmathis Thanks for opening the discussion. To be honest, I don't think the support of environment variables is necessary because a JS config file can cover the use case. For example:

export default {
  cache: process.env['YOUR_ENV_CACHE'] === 'true'
};

However, as @Mouvedia commented, we haven't yet supported the formatter config property. I'm wondering why we haven't supported it until now. 🤔

If implementing the formatter property, I image the following spec:

// stylelint.config.js
import myCustomFormatter from 'my-custom-formatter';

export default {
  // A built-in formatter name
  formatter: 'string', // | 'compact' | 'json' | ...

  // Or a path to a custom formatter module
  formatter: './path/to/my-custom-formatter.js',

  // Or a custom formatter module
  formatter: myCustomFormatter,

  rules: { /* ... */ },
};

• The --formatter or --custom-formatter CLI flags win the formatter config property.

What do you think?

[Mouvedia]

To be honest, I don't think the support of environment variables is necessary because a JS config file can cover the use case.

👍

What do you think?

Create an issue or simply update #5142.

[ybiquitous]

#5142 seems outdated. Is there a problem with rewriting this issue's title?

[ybiquitous]

Or it seems better to open a new issue. I'll do that later.