107 lines
2.8 KiB
Markdown
107 lines
2.8 KiB
Markdown
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# import/namespace
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💼 This rule is enabled in the following configs: ❗ `errors`, ☑️ `recommended`.
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<!-- end auto-generated rule header -->
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Enforces names exist at the time they are dereferenced, when imported as a full namespace (i.e. `import * as foo from './foo'; foo.bar();` will report if `bar` is not exported by `./foo`.).
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Will report at the import declaration if there are _no_ exported names found.
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Also, will report for computed references (i.e. `foo["bar"]()`).
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Reports on assignment to a member of an imported namespace.
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Note: for packages, the plugin will find exported names
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from [`jsnext:main`], if present in `package.json`.
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Redux's npm module includes this key, and thereby is lintable, for example.
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A module path that is [ignored] or not [unambiguously an ES module] will not be reported when imported.
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[ignored]: ../README.md#importignore
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[unambiguously an ES module]: https://github.com/bmeck/UnambiguousJavaScriptGrammar
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## Rule Details
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Currently, this rule does not check for possible
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redefinition of the namespace in an intermediate scope. Adherence to the ESLint
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`no-shadow` rule for namespaces will prevent this from being a problem.
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For [ES7], reports if an exported namespace would be empty (no names exported from the referenced module.)
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Given:
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```js
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// @module ./named-exports
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export const a = 1
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const b = 2
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export { b }
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const c = 3
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export { c as d }
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export class ExportedClass { }
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// ES7
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export * as deep from './deep'
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```
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and:
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```js
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// @module ./deep
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export const e = "MC2"
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```
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See what is valid and reported:
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```js
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// @module ./foo
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import * as names from './named-exports'
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function great() {
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return names.a + names.b // so great https://youtu.be/ei7mb8UxEl8
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}
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function notGreat() {
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doSomethingWith(names.c) // Reported: 'c' not found in imported namespace 'names'.
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const { a, b, c } = names // also reported, only for 'c'
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}
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// also tunnels through re-exported namespaces!
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function deepTrouble() {
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doSomethingWith(names.deep.e) // fine
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doSomethingWith(names.deep.f) // Reported: 'f' not found in deeply imported namespace 'names.deep'.
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}
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```
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### Options
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#### `allowComputed`
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Defaults to `false`. When false, will report the following:
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```js
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/*eslint import/namespace: [2, { allowComputed: false }]*/
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import * as a from './a'
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function f(x) {
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return a[x] // Unable to validate computed reference to imported namespace 'a'.
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}
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```
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When set to `true`, the above computed namespace member reference is allowed, but
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still can't be statically analyzed any further.
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## Further Reading
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- Lee Byron's [ES7] export proposal
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- [`import/ignore`] setting
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- [`jsnext:main`](Rollup)
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[ES7]: https://github.com/leebyron/ecmascript-more-export-from
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[`import/ignore`]: ../../README.md#importignore
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[`jsnext:main`]: https://github.com/rollup/rollup/wiki/jsnext:main
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