@rollup/pluginutils

A set of utility functions commonly used by 🍣 Rollup plugins.

Requirements

The plugin utils require an LTS Node version (v14.0.0+) and Rollup v1.20.0+.

Install

Using npm:

npm install @rollup/pluginutils --save-dev

Usage

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

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 or @rollup/plugin-commonjs for an example of usage.

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?: <picomatch>, exclude?: <picomatch>, options?: Object) Returns: (id: string | unknown) => boolean

include and exclude

Type: String | RegExp | Array[...String|RegExp]

A valid picomatch 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 patterns, and in most use cases, they are interchangeable. If you have more specific pattern matching needs, you can view this comparison table 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

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

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

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

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

import { normalizePath } from '@rollup/pluginutils';

normalizePath('foo\\bar'); // 'foo/bar'
normalizePath('foo/bar'); // 'foo/bar'

Meta

CONTRIBUTING

LICENSE (MIT)