Meta-ticket: Set environment for subprocesses invoked by Sage

[mkoeppe]

Instead of relying on running in an environment set up by sage-env, we should set up specific environment variables whenever we invoke executables. This will be configurable through sage_conf.

This is so that Sage is fully functional even when not being run from within sage-env. This continues what was done in #29038/#30563 for Maxima.

As this ticket removes some hard-coded paths depending on SAGE_LOCAL from sagelib, it will reduce the need for patching for downstream packaging.

A possible implementation strategy goes through sage.features.Executable.

This is part of:

• Meta-ticket: Split sage-env into 5 to clean up sage configuration #21707 Meta-ticket: Split sage-env into 5 to clean up sage configuration

Taken care of in separate tickets:

• sage.env: Remove direct uses of SAGE_LOCAL from the Sage library #32036 sage.env: Remove fallback of SAGE_LOCAL to SAGE_VENV, remove direct uses of SAGE_LOCAL from the Sage library
• sage.features.Executable: Prepend $SAGE_VENV/bin:$SAGE_LOCAL/bin to PATH #31296 sage.features.Executable: Prepend $SAGE_VENV/bin:$SAGE_LOCAL/bin to PATH, remove dependency on distutils
• QEPCAD: improve installation locations #31275 qepcad
• spkg-configure.m4 for singular #29024/sage.libs.singular: Do not fail if the Singular binary is not in PATH #33440 singular
• Add spkg-configure.m4 for 4ti2, remove direct use of SAGE_LOCAL #30887 4ti2
• sage.graphs: Use Executable.absolute_filename() #33465 sage.graphs: Use Executable.absolute_filename()
• sage.features.lrs: Make it a JoinFeature of Lrs, LrsNash; use Executable.absolute_filename #33466 lrs
• sage.geometry.polyhedron.backend_cdd: Go through sage.features for _cdd_executable #32645 cddlib
• sage.geometry: Use PalpExecutable(...).absolute_filename() #33467 palp
• Feature for gfan #33468 gfan
• Eliminate direct use of os.getenv in sage.interfaces #33405 Eliminate direct use of os.getenv in sage.interfaces
• spkg-configure.m4 for gap #29644 gap
• environment for C compiler use at runtime (includes ARCHFLAGS - see Accept /usr/bin/python3 from XCode 12.3 on macOS 10.15 (Catalina) and 11 (Big Sur) #31227)
• Set environment for sage.misc.cython #31041 environment for sage.misc.cython

CC: @kiwifb @tobiasdiez @dimpase @antonio-rojas @orlitzky @seblabbe

Component: refactoring

Keywords: sd111

Issue created by migration from https://trac.sagemath.org/ticket/30818

[mkoeppe]

comment:6

Hoping we can make progress on this ticket this week - https://wiki.sagemath.org/days111

[mkoeppe]

Changed keywords from none to sd111

[mkoeppe]

comment:13

Sage development has entered the release candidate phase for 9.3. Setting a new milestone for this ticket based on a cursory review of ticket status, priority, and last modification date.