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# @rollup/pluginutils
A set of utility functions commonly used by 🍣 Rollup plugins.
## Requirements
The plugin utils require an [LTS](https://github.com/nodejs/Release) Node version (v14.0.0+) and Rollup v1.20.0+.
## Install
Using npm:
```console
npm install @rollup/pluginutils --save-dev
```
## Usage
```js
import utils from '@rollup/pluginutils';
//...
```
## API
Available utility functions are listed below:
_Note: Parameter names immediately followed by a `?` indicate that the parameter is optional._
### addExtension
Adds an extension to a module ID if one does not exist.
Parameters: `(filename: String, ext?: String)`
Returns: `String`
```js
import { addExtension } from '@rollup/pluginutils';
export default function myPlugin(options = {}) {
return {
resolveId(code, id) {
// only adds an extension if there isn't one already
id = addExtension(id); // `foo` -> `foo.js`, `foo.js` -> `foo.js`
id = addExtension(id, '.myext'); // `foo` -> `foo.myext`, `foo.js` -> `foo.js`
}
};
}
```
### attachScopes
Attaches `Scope` objects to the relevant nodes of an AST. Each `Scope` object has a `scope.contains(name)` method that returns `true` if a given name is defined in the current scope or a parent scope.
Parameters: `(ast: Node, propertyName?: String)`
Returns: `Object`
See [rollup-plugin-inject](https://github.com/rollup/rollup-plugin-inject) or [rollup-plugin-commonjs](https://github.com/rollup/rollup-plugin-commonjs) for an example of usage.
```js
import { attachScopes } from '@rollup/pluginutils';
import { walk } from 'estree-walker';
export default function myPlugin(options = {}) {
return {
transform(code) {
const ast = this.parse(code);
let scope = attachScopes(ast, 'scope');
walk(ast, {
enter(node) {
if (node.scope) scope = node.scope;
if (!scope.contains('foo')) {
// `foo` is not defined, so if we encounter it,
// we assume it's a global
}
},
leave(node) {
if (node.scope) scope = scope.parent;
}
});
}
};
}
```
### createFilter
Constructs a filter function which can be used to determine whether or not certain modules should be operated upon.
Parameters: `(include?: , exclude?: , options?: Object)`
Returns: `(id: string | unknown) => boolean`
#### `include` and `exclude`
Type: `String | RegExp | Array[...String|RegExp]`
A valid [`picomatch`](https://github.com/micromatch/picomatch#globbing-features) pattern, or array of patterns. If `options.include` is omitted or has zero length, filter will return `true` by default. Otherwise, an ID must match one or more of the `picomatch` patterns, and must not match any of the `options.exclude` patterns.
Note that `picomatch` patterns are very similar to [`minimatch`](https://github.com/isaacs/minimatch#readme) patterns, and in most use cases, they are interchangeable. If you have more specific pattern matching needs, you can view [this comparison table](https://github.com/micromatch/picomatch#library-comparisons) to learn more about where the libraries differ.
#### `options`
##### `resolve`
Type: `String | Boolean | null`
Optionally resolves the patterns against a directory other than `process.cwd()`. If a `String` is specified, then the value will be used as the base directory. Relative paths will be resolved against `process.cwd()` first. If `false`, then the patterns will not be resolved against any directory. This can be useful if you want to create a filter for virtual module names.
#### Usage
```js
import { createFilter } from '@rollup/pluginutils';
export default function myPlugin(options = {}) {
// assume that the myPlugin accepts options of `options.include` and `options.exclude`
var filter = createFilter(options.include, options.exclude, {
resolve: '/my/base/dir'
});
return {
transform(code, id) {
if (!filter(id)) return;
// proceed with the transformation...
}
};
}
```
### dataToEsm
Transforms objects into tree-shakable ES Module imports.
Parameters: `(data: Object, options: DataToEsmOptions)`
Returns: `String`
#### `data`
Type: `Object`
An object to transform into an ES module.
#### `options`
Type: `DataToEsmOptions`
_Note: Please see the TypeScript definition for complete documentation of these options_
#### Usage
```js
import { dataToEsm } from '@rollup/pluginutils';
const esModuleSource = dataToEsm(
{
custom: 'data',
to: ['treeshake']
},
{
compact: false,
indent: '\t',
preferConst: true,
objectShorthand: true,
namedExports: true,
includeArbitraryNames: false
}
);
/*
Outputs the string ES module source:
export const custom = 'data';
export const to = ['treeshake'];
export default { custom, to };
*/
```
### extractAssignedNames
Extracts the names of all assignment targets based upon specified patterns.
Parameters: `(param: Node)`
Returns: `Array[...String]`
#### `param`
Type: `Node`
An `acorn` AST Node.
#### Usage
```js
import { extractAssignedNames } from '@rollup/pluginutils';
import { walk } from 'estree-walker';
export default function myPlugin(options = {}) {
return {
transform(code) {
const ast = this.parse(code);
walk(ast, {
enter(node) {
if (node.type === 'VariableDeclarator') {
const declaredNames = extractAssignedNames(node.id);
// do something with the declared names
// e.g. for `const {x, y: z} = ...` => declaredNames = ['x', 'z']
}
}
});
}
};
}
```
### makeLegalIdentifier
Constructs a bundle-safe identifier from a `String`.
Parameters: `(str: String)`
Returns: `String`
#### Usage
```js
import { makeLegalIdentifier } from '@rollup/pluginutils';
makeLegalIdentifier('foo-bar'); // 'foo_bar'
makeLegalIdentifier('typeof'); // '_typeof'
```
### normalizePath
Converts path separators to forward slash.
Parameters: `(filename: String)`
Returns: `String`
#### Usage
```js
import { normalizePath } from '@rollup/pluginutils';
normalizePath('foo\\bar'); // 'foo/bar'
normalizePath('foo/bar'); // 'foo/bar'
```
## Meta
[CONTRIBUTING](/.github/CONTRIBUTING.md)
[LICENSE (MIT)](/LICENSE)