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# extensions - Ensure consistent use of file extension within the import path | ||
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Some file resolve algorithms allow you to omit the file extension within the import source path. For example the `node` resolver can resolve `./foo/bar` to the absolute path `/User/someone/foo/bar.js` because the `.js` extension is resolved automatically by default. Depending on the resolver you can configure more extensions to get resolved automatically. | ||
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In order to provide a consistent use of file extensions across your code base, this rule can enforce or disallow the use of certain file extensions. | ||
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## Rule Details | ||
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This rule has one option which could be either a string or an object. If it is `"never"` (the default value) the rule forbids the use for any extension. If `"always"` then the rule enforces the use of extensions for all import statements. | ||
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By providing an object you can configure each extension separately, so for example `{ "js": "always", "json": "never" }` would always enforce the use of the `.js` extension but never allow the use of the `.json` extension. | ||
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### Exception | ||
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When disallowing the use of certain extensions this rule makes an exception and allows the use of extension when the file would not be resolvable without extension. | ||
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For example, given the following folder structure: | ||
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``` | ||
├── foo | ||
│ ├── bar.js | ||
│ ├── bar.json | ||
``` | ||
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and this import statement: | ||
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```js | ||
import bar from './foo/bar.json'; | ||
``` | ||
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then the extension can’t be omitted because it would then resolve to `./foo/bar.js`. | ||
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### Examples | ||
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The following patterns are considered problems when configuration set to "never": | ||
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```js | ||
import foo from './foo.js'; | ||
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import bar from './bar.json'; | ||
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import Component from './Component.jsx' | ||
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import express from 'express/index.js'; | ||
``` | ||
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The following patterns are not considered problems when configuration set to "never": | ||
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```js | ||
import foo from './foo'; | ||
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import bar from './bar'; | ||
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import Component from './Component' | ||
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import express from 'express/index'; | ||
``` | ||
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The following patterns are considered problems when configuration set to "always": | ||
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```js | ||
import foo from './foo'; | ||
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import bar from './bar'; | ||
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import Component from './Component' | ||
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import express from 'express'; | ||
``` | ||
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The following patterns are not considered problems when configuration set to "always": | ||
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```js | ||
import foo from './foo.js'; | ||
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import bar from './bar.json'; | ||
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import Component from './Component.jsx' | ||
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import express from 'express/index.js'; | ||
``` | ||
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## When Not To Use It | ||
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If you are not concerned about a consistent usage of file extension. |
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import path from 'path' | ||
import resolve from '../core/resolve' | ||
import endsWith from 'lodash.endsWith' | ||
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module.exports = function (context) { | ||
const configuration = context.options[0] || 'never' | ||
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function isUseOfExtensionEnforced(extension) { | ||
if (typeof configuration === 'object') { | ||
return configuration[extension] === 'always' | ||
} | ||
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return configuration === 'always' | ||
} | ||
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function isResolvableWithoutExtension(file) { | ||
const extension = path.extname(file) | ||
const fileWithoutExtension = file.slice(0, -extension.length) | ||
const resolvedFileWithoutExtension = resolve(fileWithoutExtension, context) | ||
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return resolvedFileWithoutExtension === resolve(file, context) | ||
} | ||
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function checkFileExtension(node) { | ||
const { source } = node | ||
const importPath = source.value | ||
const resolvedPath = resolve(importPath, context) | ||
const extension = path.extname(resolvedPath).substring(1) | ||
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if (!endsWith(importPath, extension)) { | ||
if (isUseOfExtensionEnforced(extension)) { | ||
context.report({ | ||
node: source, | ||
message: `Missing file extension "${extension}" for "${importPath}"`, | ||
}) | ||
} | ||
} else { | ||
if (!isUseOfExtensionEnforced(extension) && isResolvableWithoutExtension(importPath)) { | ||
context.report({ | ||
node: source, | ||
message: `Unexpected use of file extension "${extension}" for "${importPath}"`, | ||
}) | ||
} | ||
} | ||
} | ||
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return { | ||
ImportDeclaration: checkFileExtension, | ||
} | ||
} | ||
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module.exports.schema = [ | ||
{ | ||
oneOf: [ | ||
{ | ||
enum: [ 'always', 'never' ], | ||
}, | ||
{ | ||
type: 'object', | ||
patternProperties: { | ||
'.*': { enum: [ 'always', 'never' ] }, | ||
}, | ||
}, | ||
], | ||
}, | ||
] |
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{} |
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export default null |
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export default null |
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import { RuleTester } from 'eslint' | ||
import rule from 'rules/extensions'; | ||
import { test } from '../utils'; | ||
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const ruleTester = new RuleTester() | ||
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ruleTester.run('extensions', rule, { | ||
valid: [ | ||
test({ code: 'import a from "a"' }), | ||
test({ code: 'import dot from "./file.with.dot"' }), | ||
test({ | ||
code: 'import a from "a/index.js"', | ||
options: [ 'always' ] | ||
}), | ||
test({ | ||
code: 'import dot from "./file.with.dot.js"', | ||
options: [ 'always' ] | ||
}), | ||
test({ | ||
code: [ | ||
'import a from "a"', | ||
'import packageConfig from "./package.json"', | ||
].join('\n'), | ||
options: [ { json: 'always', js: 'never' } ] | ||
}), | ||
test({ | ||
code: [ | ||
'import lib from "./bar"', | ||
'import component from "./bar.jsx"', | ||
'import data from "./bar.json"' | ||
].join('\n'), | ||
options: [ 'never' ], | ||
settings: { 'import/resolve': { 'extensions': [ '.js', '.jsx', '.json' ] } } | ||
}) | ||
], | ||
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invalid: [ | ||
test({ | ||
code: 'import a from "a/index.js"', | ||
errors: [ { | ||
message: 'Unexpected use of file extension "js" for "a/index.js"', | ||
line: 1, | ||
column: 15 | ||
} ] | ||
}), | ||
test({ | ||
code: 'import a from "a"', | ||
options: [ 'always' ], | ||
errors: [ { | ||
message: 'Missing file extension "js" for "a"', | ||
line: 1, | ||
column: 15 | ||
} ] | ||
}), | ||
test({ | ||
code: 'import dot from "./file.with.dot"', | ||
options: [ "always" ], | ||
errors: [ | ||
{ | ||
message: 'Missing file extension "js" for "./file.with.dot"', | ||
line: 1, | ||
column: 17 | ||
} | ||
] | ||
}), | ||
test({ | ||
code: [ | ||
'import a from "a/index.js"', | ||
'import packageConfig from "./package"', | ||
].join('\n'), | ||
options: [ { json: 'always', js: 'never' } ], | ||
settings: { 'import/resolve': { 'extensions': [ '.js', '.json' ] } }, | ||
errors: [ | ||
{ | ||
message: 'Unexpected use of file extension "js" for "a/index.js"', | ||
line: 1, | ||
column: 15 | ||
}, | ||
{ | ||
message: 'Missing file extension "json" for "./package"', | ||
line: 2, | ||
column: 27 | ||
} | ||
] | ||
}), | ||
test({ | ||
code: [ | ||
'import lib from "./bar.js"', | ||
'import component from "./bar.jsx"', | ||
'import data from "./bar.json"' | ||
].join('\n'), | ||
options: [ 'never' ], | ||
settings: { 'import/resolve': { 'extensions': [ '.js', '.jsx', '.json' ] } }, | ||
errors: [ | ||
{ | ||
message: 'Unexpected use of file extension "js" for "./bar.js"', | ||
line: 1, | ||
column: 17 | ||
} | ||
] | ||
}), | ||
test({ | ||
code: [ | ||
'import lib from "./bar.js"', | ||
'import component from "./bar.jsx"', | ||
'import data from "./bar.json"' | ||
].join('\n'), | ||
options: [ { json: 'always', js: 'never', jsx: 'never' } ], | ||
settings: { 'import/resolve': { 'extensions': [ '.js', '.jsx', '.json' ] } }, | ||
errors: [ | ||
{ | ||
message: 'Unexpected use of file extension "js" for "./bar.js"', | ||
line: 1, | ||
column: 17 | ||
} | ||
] | ||
}) | ||
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] | ||
}) | ||
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