Split sage-env into sage-build-env and sage-env

[mkoeppe]

sage-env is used by both Sage-the-distribution while building packages, and by Sage at runtime.

It should be split into two or three separate scripts.

• sage-build-env is for the build-time environment variables for sage-the-distribution, should go into build/bin and not be installed. Or perhaps more stuff should be put into build/make/install
• sagelib-build-env is for the build-time environment variables for sagelib
• sage-env is for the run-time environment variables of sage and should be installed by src/setup.py (thus very late in the build process), rather than by build/make/Makefile. (sage-env will be very short and at some point hopefully disappear, if we want sagelib to become a standalone Python library - #21507)

This is a step towards the cleaning of src/bin as described in #21569, #21570, #21559.

[fbissey]

One comment. Currently sage_setup is installed because it needs to be installed to be doctested - like the rest of sage. But nothing in sage_setup is really needed at runtime and distro can choose not to install it. I don't in sage-on-gentoo. I tend to push for thing not needed at runtime to be moved in there. And that's where I would have put sage-build-env but I am not going to fight it going into build/bin although I'd like everything used by setup.py to be neatly under src.

[mkoeppe]

Thanks - I've updated the description

[embray]

I agree.

Consider a slight alternative: Rewrite sage-env as a Python script. This would give it much more flexibility and probably more legibility, including some command-line options for different environments (--build, especially).

The output would of course be the shell commands to actually set the variables. So rather than source sage-env one would eval $(sage-env). My one concern is that it would be slower, but ideally it's something that shouldn't happen frequently anyways, but rather only when not already in sage-env.

[fbissey]

I have a tendency to mix up sage-env the script and sage.env.py, my comment is really an example of that. However a lot is common between the two.

[embray]

Right--they could be one in the same.

[fbissey]

Replying to embray:

Right--they could be one in the same.

I have thought about it often. Of course that really means that you'll have to removing all the build time stuff. But in sage-on-gentoo where I ship a very simplified sage-env (in /etc as well) they are virtually doing the same thing, one in shell, the other in python.

[embray]

In either case--whether making a single script, or two separate shell scripts, this would be useful for gentoo (and probably other distros as well) then right?

[fbissey]

Probably, the current sage-env is a forest mostly dedicated to the build system. I just discard it and bring my own, it takes less space and maintenance than a mega patch.

[mkoeppe]

Ideally, the configuration for sagelib runtime should take place in a generated Python file and not involve environment variables at all.

[embray]

More likely parts of it would be static, and other parts could be generated, but yes, what I meant above in terms of rewriting sage-env in Python was that it would not (by default) involve environment variables at all.

But it's still useful for interacting with other tools, especially for build purposes, as well as dropping into ./sage -sh to be able to set environment variables, which is why I suggest a mode to output a list of variables that can be read from the shell.