aleclarson/module-extractor

Extract a JS/TS module and its dependencies into a new package

module-extractor

Extract a module and its dependencies into a new package

 

Usage

import { extractModules } from 'module-extractor'

const extraction = extractModules({
  // At least one entry module must be given
  entries: ['index.ts'],
  // The directory that contains package.json and source files
  pkgRoot: '/path/to/package',
  // Where to write the extracted modules and package.json
  outPkgRoot: './extracted',
})

// Called as the module graph is crawled
extraction.on('moduleAdded', module => {...})

// Called when an import statement points to an unknown file
extraction.on('moduleNotFound', (id, importer) => {...})

// Called after each tree-shaked module is written
extraction.on('moduleWritten', (filename, code, module) => {...})

// Called after the new package.json is written
extraction.on('packageCreated', (pkgJson) => {...})

// Called when the extraction is complete
extraction.then(() => {...})

 

Quirks

• Namespace imports prevent tree-shaking

  // All exports of "./foo" will be kept, even if only some are needed.
  import * as foo from './foo'

• Top-level side effects with unused return values are not preserved

  // × Not preserved in module copy!
  console.log('test')

module-extractor's Issues

Support for multiple package.json inputs

Sometimes dev dependencies can exist in a monorepo's root package.json, or maybe I have multiple entries from different packages that I want merged. In the latter case, it would probably be best to add support for an entry-specific config, like so:

// This maps "outSrcRoot" => "entry"
entries: {
  'src/foo': 'packages/foo/src/index.ts',
  'src/bar': 'packages/bar/src/index.ts',
}

Then let's add an array version of pkgRoot option. The highest common ancestor is used to compute module IDs.

pkgRoots: ['/path/to/packages/foo', '/path/to/packages/bar']

Support tsconfig.json `baseUrl` and `paths`

Projects using these compiler options aren't able to resolve their imports correctly.