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New: Configuring Additional Lint Targets with
.eslintrc (#20)
Co-Authored-By: Teddy Katz <teddy.katz@gmail.com>
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| - Start Date: 2019-05-12 | ||
| - RFC PR: https://github.com/eslint/rfcs/pull/20 | ||
| - Authors: Toru Nagashima ([@mysticatea](https://github.com/mysticatea)) | ||
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| # Configuring Additional Lint Targets with `.eslintrc` | ||
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| ## Summary | ||
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| This proposal adds the ability to specify additional target files into configuration files. This enhancement will solve the pain that people have to use the `--ext` option with wanted file extensions even if they use plugins which support additional file types. | ||
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| ## Motivation | ||
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| People have to use the `--ext` option or glob patterns to check wanted files even if they use plugins which support additional file types. | ||
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| ```yml | ||
| plugins: | ||
| - markdown | ||
| - html | ||
| - "@typescript-eslint" | ||
| - react | ||
| - vue | ||
| ``` | ||
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| ```bash | ||
| # ESLint checks only `*.js`. | ||
| eslint src docs | ||
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| # Needs `--ext` option | ||
| eslint src docs --ext .js,.md,.html,.ts,.jsx,.tsx,.vue | ||
| ``` | ||
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| However, using plugins which support additional file types is the intention that wants to check those files. The requirement of redundant CLI options is not reasonable. | ||
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| Per "[Related Discussions](#related-discussions)" section, this is very regularly requested; I want to configure additional target files with `.eslintrc`. | ||
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| ## Detailed Design | ||
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| This proposal enhances `overrides` property of the config file. | ||
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| - If a config file in a directory has `overrides` property, ESLint checks the files which are matched by any of override entries (i.e., `files`/`excludedFiles` criteria) additionally in the directory. | ||
| - If any of `files` value of an override entry ended with `*`, this enhancement doesn't use the entry in order to avoid checking too many kinds of files. | ||
| - This enhancement affects only the case where a directory path is provided on the CLI. If people provide glob patterns on the CLI, ESLint behaves the same as currently. | ||
| - The `--ext` option precedences this enhancement. If the `--ext` option was given, this enhancement is disabled. So people can use the current behavior by `--ext .js`. | ||
| - The ignoring configuration (`.eslintignore`) precedences this enhancement. If `.eslintignore` contains the additional target files, ESLint just ignores those as same as currently. | ||
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| The `overrides` property means that people intend to check those files. So this behavior is intuitive. | ||
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| <table><td> | ||
| 💡 <b>Example</b>: | ||
| <pre lang="yml"> | ||
| overrides: | ||
| - files: "*.ts" | ||
| parser: "@typescript-eslint/parser" | ||
| - files: "tests/**/*" | ||
| env: { mocha: true } | ||
| </pre> | ||
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| With the above config, `eslint .` command will check `*.ts` files additionally. But the command doesn't check all files inside `tests` directory. | ||
| </td></table> | ||
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| ### Code blocks | ||
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| If a code block that processors extracted has the virtual filename, ESLint filters the file extension of the virtual filename with `--ext` option. This enhancement affects to that check. ESLint lints the code block if the `overrides` matches the virtual filename. | ||
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| ### Legacy file extension processors | ||
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| This enhancement **doesn't** affect legacy file extension processors. This means that `plugins` property in config files never changes the kinds of target files. | ||
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| On the other hand, `extends` property in config files can change the kinds of target files by the `overrides` property in the shareable configs. | ||
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| ### Implementation | ||
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| - For files, we can add the check to [lib/cli-engine/file-enumerator.js#L410](https://github.com/eslint/eslint/blob/553795712892c8350b1780e947f65d3c019293a7/lib/cli-engine/file-enumerator.js#L410). | ||
| - For code blocks, we can add the check to [lib/cli-engine/cli-engine.js#L248](https://github.com/eslint/eslint/blob/21f3131aa1636afa8e5c01053e0e870f968425b1/lib/cli-engine/cli-engine.js#L248). | ||
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| ## Documentation | ||
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| This enhancement needs migration guide because of a breaking change. | ||
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| - If your config contains `overrides` property, `eslint` command with directory paths lints the files which are matched automatically. This may increase errors of your command.<br> | ||
| If you don't want to add file types to check, please use glob patterns instead of directory paths or `--ext .js` option. | ||
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| This enhancement, so it needs to update some documents. | ||
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| - In the description of `--ext` CLI option, it should say that your config file may add file types automatically. | ||
| - In the description of `overrides` property, it should say that the `overrides[].files` property adds target files automatically. | ||
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| ## Drawbacks | ||
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| - This is a breaking change. | ||
| - Implicit behavior may be confusing people. | ||
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| ## Backwards Compatibility Analysis | ||
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| In the following situation, `eslint` command increases errors. | ||
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| - Their configuration has `overrides` property (with `files` property which doesn't end with `*`). | ||
| - Their `eslint` command is using directory paths without `--ext` option. | ||
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| I guess that the impact is limited because people use `--ext` option or glob patterns if they use configuration which affects files other than `*.js`. | ||
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| ## Alternatives | ||
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| - To add `extensions` property that behaves as same as `--ext` option. Explicit reduces confusion. However, plugins and shareable configs cannot add the `extensions` property without the breaking change that drops old ESLint support. | ||
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| ## Open Questions | ||
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| - | ||
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| ## Frequently Asked Questions | ||
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| - | ||
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| ## Related Discussions | ||
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| - [eslint/eslint#801](https://github.com/eslint/eslint/issues/801) - Configurable Extension Filter | ||
| - [eslint/eslint#1674](https://github.com/eslint/eslint/issues/1674) - Allow setting file extensions in .eslintrc | ||
| - [eslint/eslint#2274](https://github.com/eslint/eslint/issues/2274) - Configure file extensions in .eslintrc | ||
| - [eslint/eslint#2419](https://github.com/eslint/eslint/issues/2419) - Allow configuration of default JS file types | ||
| - [eslint/eslint#7324](https://github.com/eslint/eslint/issues/7324) - File extensions in .eslintrc | ||
| - [eslint/eslint#8399](https://github.com/eslint/eslint/issues/8399) - Add .jsx to the default --ext extensions list | ||
| - [eslint/eslint#10828](https://github.com/eslint/eslint/issues/10828) - Support specifying extensions in the config | ||
| - [eslint/eslint#11223](https://github.com/eslint/eslint/issues/11223) - Add --ext to `eslintrc` or other config files |