Meta-ticket: Split sage-env into 5 to clean up sage configuration

[mkoeppe]

src/bin/sage-env (with generated configuration in src/bin/sage-env-config; installed in $SAGE_LOCAL/bin) is used in all of the following contexts:

1. Sage-the-distribution while building spkgs,
2. Sage-the-distribution for building sagelib,
3. for environment variables needed to start Sage,
4. as variables by Sage at runtime (through sage.env), and
5. for environment variables affecting subprocesses of Python invoked by sagelib modules.

This ticket proposes to split the configuration according to these 5 contexts. This will make the installation of Sage more modular and flexible.

1./2. Create build/bin/sage-build-env(with generated configuration in build/bin/sage-build-env-config) for the build-time environment variables for sage-the-distribution (spkg and sagelib). It is not installed in $SAGE_LOCAL.

1. Initially, build/bin/sage-env will call src/bin/sage-env.
2. In build/make/deps and the scripts generated by build/bin/sage-spkg, source build/bin/sage-build-env in addition to src/bin/sage-env. This is #29052.
3. Gradually, we will move settings from src/bin/sage-env[-config] to build/bin/sage-build-env[-config] that are known to be only needed for 1./2. (Note that not all compiler-related environment variables can be moved exclusively to 1./2. – some need to be added to 5 as well for some some calls to compilers needed at runtime to support things like %cython (?) and sage.calculus.desolvers.desolve_mintides.) As well as users' use of pip to install additional Python packages!
4. Eventually, we will remove the call to src/bin/sage-env.

2./3. Obtain sagelib's build-time configuration such as src/setup.py's library_dirs and runtime information (sage.env) from sage-config (introduced in #29038).

1. In src/Makefile, poison the SAGE_LOCAL variable.
2. Pass SAGE_PKGS (if still needed at all - see #28815) via sage-config instead of from src/Makefile.

3./4./5. Using sage_conf (Python module and script sage-config, #29038), make sage.all fully functional when imported from a Python, without setting any environment variables (sage-env).

1. Initially, phase out src/bin/sage-env-config by using sage-config instead.
   • #29384: Clean up src/bin/sage-env-config.in: Move logic to src/bin/sage-env, move non-environment configuration variables to sage_conf.py
2. Set sage.env variables via the Python module sage_conf instead of relying on information from environment variables. Example: CYSIGNALS_CRASH_DAYS
3. Set environment variables that are needed only by subprocesses invoked by sagelib in the environment of these subprocesses, rather than relying on them begin set in sage-env. This environment could be provided by a variable sage_conf.SAGE_SUBPROCESS_ENV and/or more invidual variables. Example: R_PROFILE
4. Finally, remove use of sage-env for all purposes except for sage -sh.

Aspects of downstream sage packaging:

• The goal is to enable downstream sage packagers to use a whole unmodified src directory to build and install sagelib.
• Downstream packagers would provide their own "implementation" (one Python module ​sage_conf.py) of the configuration module defined by #29038, instead of patching sources. They would *not* use the reference implementation in build/pkgs/sage_conf, which is intended for use with sage-the-distribution only.

Relation to the goal of sagelib as a standalone Python library (#21507)

• An sdist of sagelib, intended to be installed from source from PyPI, could package or depend on another implementation of sage_conf that calls an autoconf-generated configure script (which reuses parts of the build/pkgs/SPKG/spkg-configure.m4 infrastructure); see #29119.

More related tickets:

• cleaning of src/bin as described in #21569, #21570, #21559.
• #29133 META-META-TICKET: Build, packaging, testing improvements

[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.

[mkoeppe]

New commits:

​7405dd5	Move sage-dist-helpers from src/bin to build/bin
​9189d60	Split out build/bin/sage-build-env-config from sage-env-config

[embray]

As-is this is going to conflict with tickets like #27825 that are adding still more environment variables needed at build-time to sage-env-config.

I'm completely in favor of this separation in principle though. The question is whether we should do this first and then update tickets like #27825 on top of it, or the other way around?

[dimpase]

I really would like to first get our existing tickets (#27825, #27822) touching sage-env-config in.

[mkoeppe]

The tickets would be trivial to rebase on top of this one.

[mkoeppe]

Probably one should introduce a command sage --buildsh, which would provide the larger environment.

[embray]

For the sake of a bit more terseness I wonder if we could call it just sage-env-build.in and sage-env-build. The only reason for the -config in the other one is to distinguish it from plain sage-env.

Now that I look I'm not even entirely sure we need to separate sage-env-config from sage-env.

I think we could probably have a sage-env.in produce sage-env and get rid of the separate sage-env-config entirely, though it's possible there's some subtlety to that that I'm missing.

[embray]

Went ahead and rebased on current develop so it could incorporate all the additional variables we've since added.

I didn't change the name of the script yet; I would still prefer to shorten it but if anyone disagrees we can leave it as-is.

---

New commits:

​a34a9f1	Move sage-dist-helpers from src/bin to build/bin
​ff07121	Split out build/bin/sage-build-env-config from sage-env-config

[fbissey]

The only subtility to sage-env-config in my mind, is that you can touch it or even regenerate it without touching sage-env. But I am sure you don't need a separate file to achieve your objectives in either case.

[embray]

No, probably not. I might try it, though we'll leave that as a separate exercise from this ticket.

[embray]

Moving tickets from the Sage 8.8 milestone that have been actively worked on in the last six months to the next release milestone (optimistically).

[embray]

Ticket retargeted after milestone closed

[mkoeppe]

The run-time environment variables of sage could as well be configured by a Python module src/sage/env_config.py - see #29022.

[mkoeppe]

Replying to mkoeppe:

Probably one should introduce a command sage --buildsh, which would provide the larger environment.

As an extension of this, there could be sage --buildsh SPKG, which would set up the environment in which spkg-install runs. This could be useful for testing new versions of packages.

[mkoeppe]

Replying to mkoeppe:

The run-time environment variables of sage could as well be configured by a Python module src/sage/env_config.py - see #29022.

Or #29038 - Python package sage_conf: Provides optional configuration information for sagelib

[mkoeppe]

Hoping for input from people involved in packaging.