When to set environment variables?

[NoraLoose]

In https://github.com/CWorthy-ocean/C-Star/blob/main/cstar/base/environment.py, we set environment variables. Some of these (in particular CONDA_PREFIX) are not available to RTD. I therefore had to hardcode the following:

C-Star/docs/conf.py

Lines 24 to 25 in fc35204

	# cstar will look for os.environ["CONDA_PREFIX"] but this is not available on RTD; let's fill it with dummy
	os.environ["CONDA_PREFIX"] = str(root)

We should think about whether we can move the setting of environment variables elsewhere, so that this step only happens if you actually want to make a run (this is when the environment variables are supposedly needed?), but not upon importing cstar.

If RTD is the only case in which this logic fails, it's maybe fine, but I can imagine it will fail in other cases as well.

[TomNicholas]

Maybe let's use a context manager, see for example https://docs.xarray.dev/en/stable/user-guide/options.html. Then we could do something like

with cstar.set_environment("roms_marbl"):
    case = Case.from_yaml(...)
    case.setup()
    case.run()

Then we have automatically unset the environment variables at the point the contextmanager is exited.

[dafyddstephenson]

Maybe let's use a context manager,

I dabbled with this in #168 , but found that setting and unsetting the environment every time we needed to do something with ROMS or MARBL was leading to significant holdups, especially on machines using Linux Environment Modules to manage software.