How to downgrade a homebrew package

An upstream library has downgraded (libcerf 2.0 -> 1.14). Homebrew has followed. On a stand-alone Mac, the command brew install libcerf correctly installs v1.14. However, the same command in a .github/workflows/...macos.yml script still results in v2.0 being installed.

Where could this weird behavior come from, how to override it?

Debugging is made difficult by commands like brew show libcerf writing no output whatsoever to the GitHub Actions log.


I can reproduce the same issue.
And I have tried the few methods to install libcerf 1.14 on the macOS runner, but none of them can work.

I have created an issue ticket (actions/runner#770) to report the issue to the appropriate engineering team for further investigation and evaluation.

You can follow this issue ticket and add your comments to it.