Can't get plugin rules added by cli.addPlugin

[fisker]

Tell us about your environment

• ESLint Version: 6.5.1
• Node Version: 10.16.3
• npm Version: 6.9.0

What parser (default, Babel-ESLint, etc.) are you using?

default

const {CLIEngine} = require('eslint')
const unicorn = require('eslint-plugin-unicorn')
const cli = new CLIEngine()
cli.addPlugin('eslint-plugin-unicorn', require('eslint-plugin-unicorn'))
console.log(cli.getRules().has('unicorn/no-process-exit'))

I can't get the plugin rules, Is this by design or a bug?

---

quick reproduction

md eslint-issues-12425 && cd eslint-issues-12425 && yarn init -y && yarn add eslint eslint-plugin-unicorn

# print true
node -p "new (require('eslint').CLIEngine)({plugins: ['unicorn']}).getRules().has('unicorn/no-process-exit')"

# print false, but should be true
node -p "const cli = new (require('eslint').CLIEngine);cli.addPlugin('eslint-plugin-unicorn', require('eslint-plugin-unicorn'));cli.getRules().has('unicorn/no-process-exit')"

[fisker]

Maybe related to #11871

[mysticatea]

Thank you for your report.

That's expected because addPlugin() actually just adds the implementation of a plugin. You still need {plugins: ['unicorn']} if you don't have .eslintrc.* files. We cannot use the rules of the plugins that the configuration doesn't have.

On the other hand, it looks like a bug because

const { CLIEngine } = require('eslint')
const engine = new CLIEngine({ plugins: ["foo"] })

engine.addPlugin('foo', require('eslint-plugin-unicorn'))
console.log(engine.getRules().has('foo/no-process-exit'))

was false. I expected true in this case.

[mysticatea]

As a side note, I'm proposing to remove addPlugin() method in favor of a constructor option in RFC40.

[fisker]

The reason I check this, is because I want run plugin against plugin source, so I add cli to do this https://github.com/sindresorhus/eslint-plugin-unicorn/blob/d638e5477d7240ea777dcaf249d0121a5a1910eb/test/lint/lint.js#L11-L25 , I want make sure the plugin is loaded, but get a false result.

According to the comments above, I'm not doing it right.

I should point eslint-plugin-unicorn to local file and use .eslintrc.*, because we can't pass plugin path to engine, right?

[mysticatea]

In that case, you can use getRules() after the call of executeOnFiles() method for now.

The getRules() method returns the core rules and the rules of the plugins that the last call of executeOnFiles() or executeOnText() used.

Because, internally, the configuration object stores the loaded plugins that the config used. ESLint doesn't load plugins until configurations are determined and configurations are not determined until target files are determined. CLIEngine stores the configuration objects that the last call of executeOnFiles() or executeOnText(), then the getRules() method retrieves plugin rules from the configuration objects.

#11871 has updated CLIEngine to initialize "the configuration objects that the last call of executeOnFiles() or executeOnText() used" with only CLI options.

The addPlugin() looks to not update "the configuration objects that the last call of executeOnFiles() or executeOnText() used." (I think this is a bug because the method changes where ESLint loads plugins from.)
However, an executeOnFiles() call updates the configuration objects.

[fisker]

I remember I tried call this after executeOnFiles, because #11871 is reported by me, but also got false. anyway will try later, not on laptop now

[fisker]

Tested

$ node -p "const cli = new (require('eslint').CLIEngine);cli.addPlugin('eslint-plugin-unicorn', require('eslint-plugin-unicorn'));cli.getRules().has('unicorn/no-process-exit')"
false

$ node -p "const cli = new (require('eslint').CLIEngine)({useEslintrc: false});cli.addPlugin('eslint-plugin-unicorn', require('eslint-plugin-unicorn'));cli.executeOnText('');cli.getRules().has('unicorn/no-process-exit')"
false

$ node -p "const cli = new (require('eslint').CLIEngine)({useEslintrc: false});cli.addPlugin('eslint-plugin-unicorn', require('eslint-plugin-unicorn'));cli.executeOnFiles(['.']);cli.getRules().has('unicorn/no-process-exit')"
false

[mysticatea]

That's expected because addPlugin() actually just adds the implementation of a plugin. You still need {plugins: ['unicorn']} if you don't have .eslintrc.* files. We cannot use the rules of the plugins that the configuration doesn't have.
#12425 (comment)

[fisker]

Sorry, I miss understood it, my purpose is avoid use {plugins: ['unicorn']}, because this requires a package.json file has eslint-plugin-* as dependency.

Thanks a lot for explaining