Add ability to switch pre-build on/off

[stefanv]

TODO:

• Add test

[czgdp1807]

Seems to be working for me,

(scipy-dev) 23:53:12:~/Quansight/scipy % spin test --no-build
$ export PYTHONPATH="/Users/czgdp1807/Quansight/scipy/build-install/usr/lib/python3.12/site-packages:/Users/czgdp1807/Quansight/scipy/build-install/usr/lib/python3.12/site-packages:"
$ /Users/czgdp1807/mambaforge/envs/scipy-dev/bin/python3.12 -P -c 'import scipy'
$ cd /Users/czgdp1807/Quansight/scipy/build-install/usr/lib/python3.12/site-packages
$ /Users/czgdp1807/mambaforge/envs/scipy-dev/bin/python3.12 -P -m pytest -m 'not slow' --pyargs scipy --pyargs scipy
===================================================== test session starts ======================================================
platform darwin -- Python 3.12.0, pytest-8.3.3, pluggy-1.5.0
rootdir: /Users/czgdp1807/Quansight/scipy
configfile: pytest.ini
plugins: cov-6.0.0, hypothesis-6.121.1, timeout-2.3.1, anyio-4.6.2.post1, xdist-3.6.1
collecting 46905 items                                                                                                         ^collected 48031 items                                                                                                          

Aborted!
(scipy-dev) 23:53:53:~/Quansight/scipy % spin test           
Invoking `build` prior to running tests:
$ meson compile -j 10 -C build
INFO: autodetecting backend as ninja
INFO: calculating backend command to run: /Users/czgdp1807/mambaforge/envs/scipy-dev/bin/ninja -C /Users/czgdp1807/Quansight/scipy/build -j 10
ninja: Entering directory `/Users/czgdp1807/Quansight/scipy/build'
[2/338] Generating subprojects/highs/src/HConfig.h with a custom command
$ meson install --only-changed -C build --destdir ../build-install --tags=runtime,python-runtime,tests,devel
^C
Aborted!

So I am approving.

[czgdp1807]

Approving with reference to #272 (comment)

[czgdp1807]

@stefanv Is this PR good to go? It worked well for me.

cc: @rgommers

[ev-br]

Just to check my understanding. I've a use case now where I do in SciPy

$ python dev.py build -C-Dblas=mkl    # invoke a meson option
$ python dev.py test -t scipy/linalg/tests -v     # must not rebuild

So is this a use case this PR aims to address? If so, I'd be willing to test it. What do I need then -- this branch of spin + Gagan's SciPy PR branch?

[rgommers]

@ev-br I think the second command doesn't reconfigure the build and hence it still uses MKL. E.g., try python dev.py build -Cnonsense=true - I don't think it will choke. Hence you shouldn't need this PR.

[rgommers]

This works as advertised for me on numpy. The changes largely look good. Seems fine to merge as is, although it may be useful to make one change: I'd choose -n, --no-build as an option with a one-letter alias, just like -c, -v and -C. Adding --build as a default doesn't really do anything, and I don't see why anyone would use that.

[stefanv]

I'm happy to reduce the option to just --no-build. I'm a bit hesitant to add one-letter shortcuts. -n, e.g., is commonly used to mean dry-run. Because this option is global, it overrides every command out there. Would --no-build suffice for now?

[rgommers]

Would --no-build suffice for now?

Sure, that works too, and seems safe. If it starts getting used heavily we can always invent a one-letter acronym in the future.

[stefanv]

OK, removed the --build flag, the rest of behavior remains the same. If tests pass, @jarrodmillman this should be good to go.

[czgdp1807]

@stefanv Let's merge this PR. :-) The tests are passing.

[stefanv]

OK :)