Load environment variables script only when executing tasks.

[uptickmetachu]

We can currently set _.env to a shell script and read the exported variables into the mise environment.

It would be nice to have a _.env scoped to tasks and only executed/templated when tasks are run. This would constant execution during regular shell usage.

[jdx]

I think we could have a for="tasks" option on env._.source or something. We could also probably support having tasks.<TASK>.env._.source on the task env vars too

[egnor]

Sourcing the script (and running a bash subprocess, etc) every time there's a new shell prompt does seem a little bit much, though technically it's the only way to be entirely correct. Direnv just runs its stuff on entry to the environment and honestly that seems good for 99% of cases. Checking for modifications on the script being sourced would get you to 99.9% I think?

[uptickmetachu]

As you said sourcing the script every time is the only way to be 100% correct. Something simple like
export TIME=echo$(date) will be wrong if we only check the output after script modification.

The use case I have is setting up environment variables for a heavily parallelised build process. I could source the file before running the tasks but I would prefer to keep it consistent with having mise as the entrypoint.

I like the idea of tasks.env._.source and it does seem cleaner than adding a for option on env._.source. It was also the first I checked for in the documentation.

[jdx]

FYI there does seem to currently be a bug in "short-circuiting" logic that prevents running scripts if nothing has been changed: #1617

[jdx]

I'm a little curious how this behaves now with the hooks changes in, this may be solved now. If not, a hacky solution would be a hook on enter which just calls touch .env—though I don't know if I would call that a "solution" to this. Might be.