vercel/ncc

github/core package fails build because of exports map

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#1,311 opened on Mar 15, 2026

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bughelp wanted

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Description

The @github/core package has the following exports:

  "exports": {
    ".": {
      "types": "./lib/core.d.ts",
      "import": "./lib/core.js"
    }
  }

In a project which has type: "module", and simply import * as core from '@github/core', we get the following error:

ncc: Version 0.38.4 ncc: Compiling file index.js into ESM ncc: Using typescript@5.9.3 (local user-provided) Error: Module not found: Error: Package path . is not exported from package /code/node_modules/@actions/core (see exports field in /code/node_modules/@actions/core/package.json) Did you mean './@actions/core'?

im guessing this is because whatever throws this error is looking for a default export rather than import. or it is mistakenly looking up the non-existent CJS entrypoint.

im not sure what dependency of ncc throws this error so i haven't managed to debug it myself.

Contributor guide

Research direction
Investigate how ncc resolves package exports maps, focusing on the case where only 'import' and 'types' conditions are present, and why it might incorrectly look for a 'default' or CJS entry. Look into the dependency that throws the error and trace the module resolution logic.
Tech stack
javascripttypescriptnodejs
Domain
backendbuild systemtooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
Node.jsnpmNode.js module resolution (exports map)
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50