sage_setup: Remove import-time dependency (`setup_requires`) on `pkgconfig`, `numpy`

[mkoeppe]

Just loading src/setup.py already pulls in Cython, numpy, and pkgconfig via sage_setup, so these distributions would have to be declared as [build_system] requires in src/pyproject.toml (ex setup_requires)

By moving some computations from import-time to runtime, we get rid of this early dependency on pkgconfig, numpy. (They are, of course, still required for building the package.)

This makes setup.py sdist work using a Python that does not have numpy or pkgconfig installed. To test (with a system python that has Cython):

  $ (cd build/pkgs/sagelib/src && python3 -u setup.py --no-user-cfg sdist)

(We also reduce the load-time dependency on Cython; however, we do not address the whole load-time dependency of setup.py on Cython (via sage_setup.find, which uses open_source_file and is_package_dir) in this ticket. This is best done after #28925.)

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​88c4e8c

src/setup.py: Make 'setup.py sdist' work without Cython

[git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

​4f56517	Duplicate src/setup.py
​6fe4d56	Merge branch 't/30779/duplicate_src_setup_py' into t/30580/sage_setup__remove_import_time_dependency___setup_requires___on__pkgconfig____numpy_
​698a6ea	src/sage_setup/command/sage_build_cython.py: Remove top-level imports from sage.env, Cython
​bb32e80	build/pkgs/sagelib/src/setup.py: Make 'setup.py sdist' work without Cython

[mkoeppe]

Ready for review.

[dimpase]

the 1st line of the output seems to try to say something about --version I don't get:

$ python3 -u setup.py --no-user-cfg sdist >/tmp/res
/bin/sh: 1: --version: not found
distributions = ['']
warning: sdist: standard file not found: should have one of README, README.txt, README.rst

warning: no files found matching '*.hh' anywhere in distribution
...

[mkoeppe]

Replying to dimpase:

the 1st line of the output seems to try to say something about --version I don't get:

$ python3 -u setup.py --no-user-cfg sdist >/tmp/res
/bin/sh: 1: --version: not found

This is from src/sage_setup/command/sage_build_cython.py:

# Work around GCC-4.8 bug which miscompiles some sig_on() statements:
# * http://trac.sagemath.org/sage_trac/ticket/14460
# * http://trac.sagemath.org/sage_trac/ticket/20226
# * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56982
if subprocess.call("""$CC --version | grep -i 'gcc.* 4[.]8' >/dev/null """, shell=True) == 0:
    extra_compile_args.append('-fno-tree-copyrename')

This gives an (ignored) error when CC is not set -- this defect is not new in this ticket.

[dimpase]

Do we need to support gcc 4.8 ? The last release of gcc 4.8.* was over 5 years ago.

[dimpase]

lgtm - the gcc version could be bumped elsewhere

[mkoeppe]

Replying to dimpase:

Do we need to support gcc 4.8 ? The last release of gcc 4.8.* was over 5 years ago.

Yes until we drop ubuntu trusty and similar.

[mkoeppe]

Thanks for the review! I have opened #30876 for the issue with the unset CC environment variable.

[vbraun]

Merge conflict

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​f53bc50	Merge commit 'cc96c6dbae448cd361e798a1f29ec5bf10b0c57b' of git://trac.sagemath.org/sage into t/30580/sage_setup__remove_import_time_dependency___setup_requires___on__pkgconfig____numpy_
​8f04684	Merge tag '9.3.beta2' into t/30580/sage_setup__remove_import_time_dependency___setup_requires___on__pkgconfig____numpy_