These checks are already available at runtime (as matplotlib.checkdep_foo), when the check is arguably more useful (it is not like a build time option where we actually need to build a different version of matplotlib depending on whether tex is available; even with tex not present I can just first install matplotlib and then install tex and everything will work fine).

It is nice to catch the warning when you install rather than when something fails.

But this only gets executed when installing from source rather than from a wheel or a conda package (which is likely the most common case where the warning would be useful...).

Can we move this to (or do we already have?) a utility function at in the top level namespace like check_latex_installation() -> Dict[packag_name, version or None]?

You mean these? :-)

In [7]: matplotlib.checkdep_dvipng()
Out[7]: '1.15'

In [8]: matplotlib.checkdep_tex()
/usr/bin/ipython:1: MatplotlibDeprecationWarning: The checkdep_tex function was deprecated in version 2.1.
  #!/usr/bin/python3
Out[8]: '3.14159265'

In [9]: matplotlib.checkdep_ghostscript()
Out[9]: ('gs', '9.22')

(and a few others)

We could unify all these into something like

matplotlib.list_installed_executables()
--->
{"depname": ("dep_executable", "version") or None}

(also including gs and inkscape, so not just latex deps)

Yes, those. We should bundle them up into one summary function?

That's what I proposed above (but you may have missed the edit :-))

👍