vitest-package-exports

An Vitest util to get all exported APIs of a package and prevent unintended breaking changes.

Install

npm i -D vitest-package-exports

Update your Vitest config:

export default defineConfig({
  test: {
    server: {
      deps: {
        inline: [
          'vitest-package-exports',
        ],
      },
    },
  },
})

Usage

A typical usage is to make a snapshot to freeze the exported APIs of a package:

import { fileURLToPath } from 'node:url'
import { expect, it } from 'vitest'
import { getPackageExportsManifest } from 'vitest-package-exports'

it('exports snapshot', async () => {
  const manifest = await getPackageExportsManifest({
    importMode: 'src', // or 'dist' or 'package'
    cwd: fileURLToPath(import.meta.url),
  })

  expect(manifest.exports)
    .toMatchInlineSnapshot(`
      {
        ".": {
          "getPackageExportsManifest": "function",
        },
      }
    `)
})

Everytime you adding or remove the exported APIs, the snapshot will break and requires explicit review. This would help you to catch unintended breaking changes, or unintentional internal leaks.

For example, if I renamed the getPackageExportsManifest function to getPackageExportsManifestRenamed, the test will fail until I update the snapshot:

import { fileURLToPath } from 'node:url'
import yaml from 'js-yaml' // <---
import { expect, it } from 'vitest'
import { getPackageExportsManifest } from 'vitest-package-exports'

it('exports snapshot', async () => {
  const manifest = await getPackageExportsManifest({
    importMode: 'src',
    cwd: fileURLToPath(import.meta.url),
  })

  expect(yaml.dump(manifest.exports)) // <---
    .toMatchInlineSnapshot(`
      .:
        getPackageExportsManifest: function
    `)
})

Monorepo Usage

Since this utility is only a function, you can compose it freely to fit your monorepo structure.

If you want to snapshot all packages in your pnpm monorepo, here is an example we use in VueUse:

import yaml from 'js-yaml'
import { x } from 'tinyexec'
import { describe, expect, it } from 'vitest'
import { getPackageExportsManifest } from 'vitest-package-exports'

describe('exports-snapshot', async () => {
  const packages: { name: string, path: string, private?: boolean }[] = JSON.parse(
    await x('pnpm', ['ls', '--only-projects', '-r', '--json']).then(r => r.stdout),
  )

  for (const pkg of packages) {
    if (pkg.private)
      continue
    it(`${pkg.name}`, async () => {
      const manifest = await getPackageExportsManifest({
        importMode: 'src',
        cwd: pkg.path,
      })
      await expect(yaml.dump(manifest.exports, { sortKeys: (a, b) => a.localeCompare(b) }))
        .toMatchFileSnapshot(`./exports/${pkg.name.split('/').pop()}.yaml`)
    })
  }
})

This will create a file snapshot for each package in the ./exports directory.

How it works

When getPackageExportsManifest is called, it will:

1. Find the package.json file in the current working directory.
2. Parse the exports field in the package.json file.
3. Depend on the importMode, it will resolve the exports to the corresponding import path.

• package: Import from package name directly, for example import('vitest/config')
• dist: Import the module from the defined exports entry, for example import('./dist/config.mjs')
• src: Import the module from the src directory (replace dist with src), for example import('./src/config.ts')
  • This assume your codebase is structure as src -> dist with one-to-one mapping. If you have a custom build process, provide resolveSourcePath option to write your own mapping logic.

4. For each entry, it will import the module at runtime to get the exports object. Essentially Object.keys(await import(entry)) (so it’s better to only use this in sandboxed environments like Vitest)
5. Return the manifest of the exported APIs.

FAQ

Does this Requires Vitest?

Actually not necessary, this utility does not directly depend on Vitest, but it’s designed to work with Vitest. Internally it use dynamic import() to get the exports object, it would work best in Vitest as it will provide proper resolution of the import path, while also supporting your alias config if any.

I named this under vitest- to give a clear expection. Feel free to use it in other context or even plain Node.js, but no guarantee from our side. Please do your own research.

Sponsors

License

MIT License © Anthony Fu