Compile everything with meson

[tobiasdiez]

Add meson configuration to compile sagelib with meson. Basic developer docs are added as well (meant as background info, not real installation instructions and thus under "developer").

📝 Checklist

• The title is concise, informative, and self-explanatory.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

⌛ Dependencies

[mkoeppe]

Note that the sage.categories namespace package is not shipped by one distribution, but rather split into two distribution packages - sagemath-objects and sagemath-categories.

[tobiasdiez]

Note that the sage.categories namespace package is not shipped by one distribution, but rather split into two distribution packages - sagemath-objects and sagemath-categories.

I don't see how this is relevant here. I'm trying to build the full sagelib with meson. Just started with a small part to make reviewing easier

[mkoeppe]

Just a heads up that the monolithic build is going to go away very soon. So it would be unwise to design a new system for the monolithic library.

[tobiasdiez]

The separation of sage-the-distribution and sage-the-software is what I advocated years and years ago. I worked on it, got some results, but lost patience... I would be happy to see it come to reality though.

Thanks. @kiwifb - what do you think about this?

I am really interested to see meson being adopted as the build system for sagelib/sagemath-standard.

Happy to hear!

I do not like the presence of the top meson.build file, unless I can do without it.

The top meson.build file is very similar to the top make file, it gives the central starting point to compile the whole sage-library, as well as running tests (and compiling the docs in the future). I kept the requirements of the modularized distributions in mind when I designed the meson files: a modularized distro just needs to provide its own "top-level" meson build file that specifies its name and sets a few variables that control what source files to install and what the required dependencies are. But developing this in detail goes beyond the scope of this PR.

[tobiasdiez]

I've cleanup the PR a bit more. In particular, I've removed all the __init__ files from source, and auto-generate them on build time. So hopefully this unblocks the PR.

The installation with build isolation should work now as well.

@dimpase @orlitzky @kiwifb please try it, following the instructions in the newly added meson.rst and let me know if you encounter any errors.

[orlitzky]

I'm between hardware right now but I have missed this dearly over the past few weeks. How will I know it's working if it doesn't take me...

$ time (./bootstrap && sage-configure)
...
real	11m31.481s
user	18m33.386s
sys	2m21.382s

eleven and a half minutes to run meson setup?

[dimpase]

./bootstrap has been horrendously slow lately. Not the least as it spawns hundreds of python processes at some point.

And unconditionally generates conda config files, without checking whether we are on conda, or not.

And your macros to handle system Python packages are very slow, as creating venv for every package is not fast...

(sorry, I realised I was talking about the standard setup, not about this PR. But bootstrap being slow does not surprise me at all)

[tobiasdiez]

Neither bootstrap nor sage-configure are needed for meson. It generates all the files it needs during build time (like it should).