nodejs / nodejs/node

Publish `exports` and `imports` implementations as separate module(s)

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esm feature request module never-stale
Dominant language
JavaScript
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Description

What is the problem this feature will solve?

Projects implementing support for module resolution have to add support for the quite advanced exports and imports fields in package.json.

https://nodejs.org/api/packages.html#exports
https://nodejs.org/api/packages.html#imports

Examples of projects that have done this are Webpack, TypeScript, Jest (only exports, not imports), Yarn and probably more. AFAIK neither Rollup, Parcel or Metro (to name some bundlers) have support.

What is the feature you are proposing to solve the problem?

If the algorithm Node uses internally was published as a separate module, I hope (and believe) more projects would be able to add support more readily, and that ecosystem compatibility would improve as a result.

I think part of the reason is the complexity in supporting the algorithm needed, particularly with subpath exports, wildcards and conditionals. E.g. https://github.com/browserify/resolve/issues/222 is stuck, and https://github.com/facebook/jest/issues/9771 took a long time.

Prior art for externalizing parts of Node publishing cjs-module-lexer separately, which means Jest could implement the same feature as node itself when importing CJS from ESM (via vm API).


Note that this is not a request for the full require or ESM resolution algorithm. This is solely a request for "given this exports/imports, this specifier and these conditions, what path does it map to" - no FS access/lookups at all. API similar to https://github.com/lukeed/resolve.exports makes sense to me.

What alternatives have you considered?

Jest (and Yarn) currently use https://github.com/lukeed/resolve.exports to avoid having to implement all the resolution. It currently does not support imports (https://github.com/lukeed/resolve.exports/issues/14).

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the linked Node.js documentation for package exports and imports, then compare the cited resolve.exports module and related examples. Define the scope of a standalone implementation that maps a specifier and conditions without filesystem access; done means the proposed module covers exports and imports while remaining separate from full require or ESM resolution.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript, node.js
Domain
developer-experience, tooling
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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