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  • Start Date: 2019-05-12
  • RFC PR: #22
  • Authors: Toru Nagashima (@mysticatea)

Configuring core options in Config Files

Summary

This RFC adds several properties into config files to configure core options. People can use config files (including shareable configs!) instead of CLI options in order to configure some linter behavior.

Motivation

We cannot configure some linter's behavior with config files, especially, shareable configs. It's convenient if we can configure those in shareable configs.

Detailed Design

This RFC adds four properties to config files.

// .eslintrc.js
module.exports = {
    noInlineConfig: false,              // Corresponds to --no-inline-config
    reportUnusedDisableDirectives: false,    // Corresponds to --report-unused-disable-directives
    verifyOnRecoverableParsingErrors: false, // Corresponds to --verify-on-recoverable-parsing-errors
    ignorePatterns: [],                      // Corresponds to --ignore-pattern

    overrides: [
        {
            files: ["*.ts"],
            noInlineConfig: false,
            reportUnusedDisableDirectives: false,
            verifyOnRecoverableParsingErrors: false,
            // ignorePatterns: [], // Forbid this to avoid confusion with 'excludedFiles' property.
        },
    ],
}

§ noInlineConfig

That value can be a boolean value. Default is false.

If true then it disables inline directive comments such as /*eslint-disable*/.

If noInlineConfig is true, --no-inline-config was not given, and there are one or more directive comments, then ESLint reports each directive comment as a warning message (severify=1). For example, "'eslint-disable' comment was ignored because your config file has 'noInlineConfig' setting.". Therefore, end-users can know why directive comments didn't work.

💠Implementation:

In Linter#_verifyWithoutProcessors method, the linter checks both providedConfig and filenameOrOptions to determine noInlineConfig option. The filenameOrOptions.allowInlineConfig precedences providedConfig.noInlineConfig.

§ reportUnusedDisableDirectives

That value can be a boolean value. Default is false.

If true then it reports directive comments like //eslint-disable-line when no errors would have been reported on that line anyway.

This option is different a bit from --report-unused-disable-directives CLI option. The --report-unused-disable-directives CLI option fails the linting with non-zero exit code (i.e., it's the same behavior as severity=2), but this reportUnusedDisableDirectives setting doesn't fail the linting (i.e., it's the same behavior as severity=1). Therefore, we cannot configure ESLint with reportUnusedDisableDirectives as failed by patch releases.

💠Implementation:
  1. Linter and CLIEngine have options.reportUnusedDisableDirectives. This RFC enhances these options to accept "off", "warn", and "error". Existing false is the same as "off" and existing true is the same as "error".
  2. In Linter#_verifyWithoutProcessors method, the linter checks both providedConfig and filenameOrOptions to determine reportUnusedDisableDirectives option. The filenameOrOptions.reportUnusedDisableDirectives precedences providedConfig.reportUnusedDisableDirectives.

§ verifyOnRecoverableParsingErrors

That value can be a boolean value. Default is false.

If true then it runs rules even if recoverable errors existed. Then it shows both results.

💠Implementation:

In Linter#_verifyWithoutProcessors method, the linter checks both providedConfig and filenameOrOptions to determine verifyOnRecoverableParsingErrors option. The filenameOrOptions.verifyOnRecoverableParsingErrors precedences providedConfig.verifyOnRecoverableParsingErrors.

§ ignorePatterns

That value can be an array of strings. Default is an empty array.

This is very similar to .eslintignore file. Each value is a file pattern as same as each line of .eslintignore file. ESLint compares the path to source code files and the file pattern then it ignores the file if it was matched. The path to source code files is addressed as relative to the entry config file, as same as files/excludedFiles properties.

ESLint concatenates all ignore patterns from all of .eslintignore, --ignore-path, --ignore-pattern, and ignorePatterns. If there are multiple ignorePatterns in a ConfigArray, all of them are concatenated. The order is:

  1. The default ignoring. (I.e. .*, node_modules/*, and bower_components/*)
  2. ignorePatterns in the appearance order in the config array.
  3. --ignore-path or .eslintignore.
  4. --ignore-pattern

Negative patterns mean unignoring. For example, !.*.js makes ESLint checking JavaScript files which start with .. Negative patterns are used to override parent settings. Also, negative patterns is worthful for shareable configs of some platforms. For example, the config of VuePress can provide the configuration that unignores .vuepress directory.

It disallows ignorePatterns property in overrides entries in order to avoid confusion with excludedFiles. And if a ignorePatterns property came from shareable configs in overrides entries, ESLint ignores it. This is the same behavior as root property.

The --no-ignore CLI option disables ignorePatterns as well.

💠Implementation:

§ Other options?

  • extensions - This RFC doesn't add extensions option that corresponds to --ext because #20 "Configuring Additional Lint Targets with .eslintrc" is the good successor of that.
  • rulePaths - This RFC doesn't add rulePaths option that corresponds to --rulesdir because #14 (localPlugins) is the good successor of that. Because the rulePaths doesn't have namespace, shareable configs should not be able to configure that. (Or but it may be useful for some plugins such as @typescript-eslint/eslint-plugin in order to replace core rules. I'd like to discuss the replacement way in another place.)
  • format - This RFC doesn't add format option that corresponds to --format because it doesn't fit cascading configs. It needs another mechanism.
  • maxWarnings - This RFC doesn't add maxWarnings option that corresponds to --max-warnings because it doesn't fit cascading configs. It needs another mechanism.

Documentation

Drawbacks

Nothing in particular.

Backwards Compatibility Analysis

No concerns. Currently, unknown top-level properties are a fatal error.

Alternatives

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