Summary

changeset publish crashes with pnpm as the package manager, in any environment where the underlying npm binary is npm 12+ (e.g. after a npm install -g npm@latest step in CI, which is common right before a release job):

TypeError: Cannot read properties of undefined (reading 'includes')
at getUnpublishedPackages (.../@changesets/cli/dist/getPublishPlan.mjs:613:26)
at process.processTicksAndRejections (node:internal/process/task_queues:104:5)
at async getPublishPlan (.../getPublishPlan.mjs:665:19)
at async publish (.../publish.mjs:70:96)

Root cause

On pnpm ≤10, pnpm info/pnpm view is not a native pnpm command — it's passed straight through to the system's npm binary (see pnpm/src/pnpm.ts, the passThruToNpm() case list includes info/view). So pnpm info <pkg> --json on pnpm 10.x is really just npm view <pkg> --json under the hood, using whatever npm is currently resolvable on PATH (packages exec/run-npm/src/index.ts: const npm = npmPath ?? 'npm').

npm 12.0.0 changed npm view <pkg> --json to always wrap its result in an array ([ {...} ]) instead of returning a bare object — this is exactly what #2164 reported and was fixed for, in the pre-v3 npm-utils.ts's getPackageInfo().

That fix correctly carried over into the new npm.ts after the publish-flow split in #2155 (parseInfoResult$1/the npm tool's parseInfoResult explicitly does Array.isArray(parsed) ? { info: parsed[0] } : { info: parsed }), but the equivalent guard was not added to the new pnpm.ts's parseInfoResult:

// packages/cli/src/lib/pnpm.ts
function parseInfoResult({ exitCode, stdout, stderr }) {
  if (exitCode !== 0) return { error: getPnpmError(stderr, stdout) }
  return stdout ? { info: JSON.parse(stdout) } : undefined   // <-- no array unwrap
}

Since pnpm ≤10 delegates to the same underlying npm view, it hits the exact same npm-12 array-wrapping — but because pnpm.ts's parser stores the array as-is in response.info, response.info.versions is undefined, and getUnpublishedPackages crashes calling .includes() on it in getPublishPlan.ts.

Reproduction

• @changesets/cli 3.0.1
• Any pnpm ≤10 (tested 10.33.0)
• npm 12.0.0+ resolvable on PATH (e.g. right after npm install -g npm@latest)
• Publish a package that's already on the registry (or run changeset publish with no changesets) → crash instead of "already published" / "no unpublished projects" message.