[dahai80]

Summary

On macOS the action unconditionally overwrites AGENT_TOOLSDIRECTORY with the hosted-images default /Users/runner/hostedtoolcache:

src/setup-python.ts:

if (IS_MAC) {
  process.env['AGENT_TOOLSDIRECTORY'] = '/Users/runner/hostedtoolcache';
}

Self-hosted macOS runners export their own AGENT_TOOLSDIRECTORY / RUNNER_TOOL_CACHE in the runner service environment. The hardcode discards both, so the downloaded setup.sh runs mkdir -p /Users/runner/hostedtoolcache and fails with mkdir: /Users/runner: Permission denied on hosts that have no runner user account.

Reproduction

Self-hosted macOS runner with RUNNER_TOOL_CACHE/AGENT_TOOLSDIRECTORY exported via the service wrapper (verified present in both bash and node step env), any actions/setup-python@v7 step that needs to download a Python version fails at the archive's install script:

Version 3.11 was not found in the local cache
Download from .../python-3.11.9-darwin-arm64.tar.gz
Execute installation script
Check if Python hostedtoolcache folder exist...
Creating Python hostedtoolcache folder...
##[error]mkdir: /Users/runner: Permission denied

Change

Fall back to /Users/runner/hostedtoolcache only when the runner did not provide a non-empty AGENT_TOOLSDIRECTORY. Behavior on GitHub-hosted macOS images is unchanged (they set AGENT_TOOLSDIRECTORY=/Users/runner/hostedtoolcache explicitly or the fallback applies identically).

Validation

• Self-hosted macOS runner (Apple Silicon, macOS 26) with RUNNER_TOOL_CACHE/AGENT_TOOLSDIRECTORY pointing to a writable custom dir: previously every setup-python step failed with the mkdir error above; with the patched action logic the same step resolves the install dir from the runner-provided path.
• Hosted macOS behavior: AGENT_TOOLSDIRECTORY is either pre-set by the image (unchanged) or the fallback applies (identical to current behavior).

Fixes #914 (macOS variant; the Linux /opt/hostedtoolcache symptom reported there has a separate code path)

🤖 Generated with Claude Code