Errors in post-install when called via composite action

[haines]

2026-05-08T14:40:00.6826488Z ##[group]Run pnpm/action-setup@8912a9102ac27614460f54aedde9e1e7f9aec20d
2026-05-08T14:40:00.6826992Z with:
2026-05-08T14:40:00.6827214Z   cache: true
2026-05-08T14:40:00.6827527Z   cache_dependency_path: frontend/pnpm-lock.yaml
2026-05-08T14:40:00.6827954Z   package_json_file: frontend/package.json
2026-05-08T14:40:00.6828325Z   run_install: cwd: frontend

2026-05-08T14:40:00.6828652Z   dest: ~/setup-pnpm
2026-05-08T14:40:00.6828919Z   standalone: false
2026-05-08T14:40:00.6830293Z ##[endgroup]

...

2026-05-08T14:42:24.9157219Z Post job cleanup.
2026-05-08T14:42:25.1099335Z ##[error]Error for input "run_install" = cwd:
2026-05-08T14:42:25.1103403Z ##[error]Errors: [object Object]

There seems to be two problems here. One is that printing the Zod error here doesn't work properly so we just get [object Object] in the logs. I guess that needs a JSON.stringify or something.

The other one is that it seems to have received two different inputs for the initial run of the action and the post-install step 🤯 This may be because we call pnpm/action-setup via a composite action:

• Composite: Nested actions post steps have the wrong context actions/runner#2030
• Wrong environment passed to node post when called by composite called by composite action actions/runner#3514

The recommended fix (see devcontainers/ci#442) is

persist inputs in main using saveState, then read them back from STATE_* in the post step

Even GitHub's own actions have had to work around this bug in the runner: github/codeql-action#2557 😳