Before:

sage: sage.env.MATHJAX_DIR
''

After:

sage: sage.env.MATHJAX_DIR
'/usr/share/mathjax'

The test failure in Conda (ubuntu, Python 3.12, new) is not new, it was also there the last time env.py was touched:

https://github.com/sagemath/sage/pull/40152/files

It's a # long time test so it's only run when the file is modified.

I'm a bit torn. On the one hand this is a sensible, quick fix. On the other hand, I agree with your

In the long term we should fix the env.py/config.py duplication and centralize the variable settings and fallbacks in a single place.

Since with #39030, sage-the-distro uses the meson backend as well, we can already start this consolidation. So here I would propose to:

• Detect Mathjax in meson, with fallback to the cdn, export to config.py
• Remove Mathjax stuff from env.py
• Directly use the Mathjax path as determined via meson in the doctest conf.py
• Remove the Mathjax spkg

That sounds reasonable. My main concern is that it sounds like a big change and we are quite late in the 10.7 cycle, so I'm not sure it will make it on time. I was hoping to ship 10.7 built with meson and this fix is required to build docs in that case (of course I can always patch stuff downstream, but it's better not to have to).

Okay, good point.

I've started working (or better let copilot work) on the matjax migration to meson config in #40404.