Equation label of math not work before `make clean` when math_numfig=True

[berlin2123]

Here is the initial description of the phenomenon, but the bug is not really related to the Dollar math. Actual testing of directive math does the same issue. See comment 3.

I want to using math_numfig to show equation label like (m.n) instead of (n).

However, the dollar math shows a empty (), when:

math_numfig = True
numfig = True
numfig_secnum_depth = 2

but the directive {math} works fine.

here is the test.md

{math}`a^2 + b^2 = c^2`

```{math} e^{i\pi} + 1 = 0
:label: euler
```                                          #(just show this ``` inside github)
$$a^2 + b^2 = c^2$$(label: mymath3)

Error, when using numfig: empty ()

Fine, when disabled numfig: type as (n)

However, that not what I wanted type (1.2).

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[berlin2123]

I've identified the real issue:

After add a new dollar math with a label, if only run make html or just only using sphinx-autobuild, it will be a empty () . However, after make clean; make html, all lable will be fine.

It may be a bug related to the build process.

[berlin2123]

the same issue for directive math too. Regardless of whether the newly added formula is writen as directive or dollar, you have to run make clean before it works.

[berlin2123]

So it could be a bug in sphix, not MyST ?

[chrisjsewell]

Yep it sounds like it. Perhaps you could try a math directive in a restructuredtext file

[berlin2123]

the same issue for adding math in a rst file.

[berlin2123]

fixed by https://github.com/sphinx-doc/sphinx/pull/11939