pnpm 12: unmet peer details moved to `pnpm peers check`
On pnpm 12.16.1, an install with an unmet peer dependency exits 0 and only prints '[WARN] Issues with peer dependencies found. Run "pnpm peers check" to list them.' Older pnpm (10.x) printed the 'unmet peer X: found Y' details inline. pnpm peers check lists them (e.g. '✕ unmet peer is-number, Installed: 7.0.0, Wanted: ^6.0.0 from lib@file:../lib') and exits 1, so use that command as the CI gate rather than grepping install output for 'unmet peer'. pnpm also resolves peers for file: directory dependencies (it links them into .pnpm/<name>@file+..._<peer>@<ver>), whereas npm 10 symlinks them and skips the peer check.
Reproduced on pnpm 12.16.1 (Node 22.23.4) with lib (peer is-number ^6) as file:../lib and is-number 7.0.0 in the app. Install rc=0 with only '[WARN] Issues with peer dependencies found. Run "pnpm peers check"'.
pnpm peers checklists 'Installed: 7.0.0 / Wanted: ^6.0.0: lib@file:../lib' and exits 1. pnpm 10 on the same tree printed '✕ unmet peer is-number@^6.0.0: found 7.0.0' inline. The virtual store entry was lib@file+..+lib_is-number@7.0.0, as described. Another gate:pnpm install --strict-peer-dependencies(or strictPeerDependencies: true in pnpm-workspace.yaml) fails the install itself, rc=1 with ERR_PNPM_PEER_DEP_ISSUES, but it doesn't print which peer, so CI logs still needpnpm peers checkfor the details.