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codeql-action/node_modules/eslint-plugin-import/docs/rules/unambiguous.md
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# import/unambiguous | |
<!-- end auto-generated rule header --> | |
Warn if a `module` could be mistakenly parsed as a `script` by a consumer leveraging | |
[Unambiguous JavaScript Grammar] to determine correct parsing goal. | |
Will respect the [`parserOptions.sourceType`] from ESLint config, i.e. files parsed | |
as `script` per that setting will not be reported. | |
This plugin uses [Unambiguous JavaScript Grammar] internally to decide whether | |
dependencies should be parsed as modules and searched for exports matching the | |
`import`ed names, so it may be beneficial to keep this rule on even if your application | |
will run in an explicit `module`-only environment. | |
## Rule Details | |
For files parsed as `module` by ESLint, the following are valid: | |
```js | |
import 'foo' | |
function x() { return 42 } | |
``` | |
```js | |
export function x() { return 42 } | |
``` | |
```js | |
(function x() { return 42 })() | |
export {} // simple way to mark side-effects-only file as 'module' without any imports/exports | |
``` | |
...whereas the following file would be reported: | |
```js | |
(function x() { return 42 })() | |
``` | |
## When Not To Use It | |
If your application environment will always know via [some other means](https://github.com/nodejs/node-eps/issues/13) | |
how to parse, regardless of syntax, you may not need this rule. | |
Remember, though, that this plugin uses this strategy internally, so if you were | |
to `import` from a module with no `import`s or `export`s, this plugin would not | |
report it as it would not be clear whether it should be considered a `script` or | |
a `module`. | |
## Further Reading | |
- [Unambiguous JavaScript Grammar] | |
- [`parserOptions.sourceType`] | |
- [node-eps#13](https://github.com/nodejs/node-eps/issues/13) | |
[`parserOptions.sourceType`]: https://eslint.org/docs/user-guide/configuring#specifying-parser-options | |
[Unambiguous JavaScript Grammar]: https://github.com/nodejs/node-eps/blob/HEAD/002-es-modules.md#32-determining-if-source-is-an-es-module |