`--shell` does not work for global agent hooks

[markmssd]

I've been reading through the docs, and trying to set the agent shell option, hoping it would also run the agent global hooks.

What I'm trying is to use PowerShell v7. I've tried

• using the cli argument --shell
• adding shell=... to the agent config file
• setting the environment variable BUILDKITE_SHELL

I've tried setting the value to many things:

• C:\Program Files\PowerShell\7\pwsh.exe
• pwsh
• pwsh -Command

I've also tried to call pwsh from within the hook, for example:

$scriptBlock = @{
  # the actual script 
}

pwsh ${scriptBlock}

This worked for the environment.ps1 hook, but not in the others, not sure why 🤔

However the agent hooks always execute with PowerShell v5 instead. I'd prefer v7 since it's cross-platform, and would make it much easier to maintain the hooks (only need to be written once).

Is there a way to achieve this? Happy to contribute to a PR if needed. Thanks!

[scadu]

Hey @markmssd 👋

Thanks for raising the issue.

The BUILDKITE_SHELL variable is only used to define a shall interpreting build commands.
So agent hooks would be out of scope.

For nix-like environments, agent would read hook's extension, and when missing, a shebang to use a correct interpreter.
In case of Windows, .ps1 files would be executed by powershell.exe as you've noticed.
I totally understand the desire to use PowerShell 7 (pwsh.exe) which doesn't seem to be supported at the moment, so that's a valuable feedback for us.
Before raising any pull request though, let me consult internally what would be the best way forward in here. We definitely wouldn't want to break existing installations where PowerShell 5 is in use!

---

I'm curious to learn about what you've tried so far. You have mentioned that calling pwsh from within the environment.ps1 hook worked – does it mean you were able to export environment variables from the child pwsh to the parent powershell.exe?

[markmssd]

Hey @scadu!

What I've tried so far is setting the agent's configuration:

• --shell=C:\Program Files\PowerShell\7\pwsh.exe cli argument
• the shell=C:\Program Files\PowerShell\7\pwsh.exe configuration in C:\buildkite-agent\buildkite-agent.cfg
• and the BUILDKITE_SHELL=C:\Program Files\PowerShell\7\pwsh.exe

does it mean you were able to export environment variables from the child pwsh to the parent powershell.exe

I don't remember if that actually worked, the next agent hooks were still running with PS v5. The way I check it is by running the $PSVersionTable within each hook.

Before raising any pull request though, let me consult internally what would be the best way forward in here. We definitely wouldn't want to break existing installations where PowerShell 5 is in use!
Got it! Let me know once you discuss it internally. Not sure what would be a good way to support it without breaking anything. Perhaps:

• a new BUILDKITE_HOOKS_SHELL
• support shebang in .ps1 files too, pointing to PS7
• In the next major release, make BUILDKITE_SHELL apply for hooks scripts too - and in the meantime, have an experimental flag to use this behaviour
• something else?