Latex macros broken

[Sr-11]

Description

Reproduce:
create test.ipynb with 2 lines:

$\newcommand{\a}{\alpha}$
$\a$

Open jupyter in a conda env with jupyterlab-myst installed, the output is
.
But if I use a env with no jupyterlab-myst, it renders as $\alpha$.

[drmikecooke]

I have the same problem with jupyter-lab installed via pipx. The jupyter-lab version is 4.4.0. The jupyterlab-myst extension seems to be version 2.4.2. I installed it to try and simulate jupyter book output better, but to be honest it wasn't even good for that. I will leave it disabled for now. The behavior is as above, e.g.

$\newcommand{ve}{\varepsilon}$
$\ve$

(I found by accident that newcommand doesn't need the escape/backslash to define the code.)

With myst enabled it gives the dotted circle and the undefined sequence (don't know how to transfer this here). But disabled it gives my desired code for $\varepsilon$.

[rowanc1]

This is currently unsupported in mystmd and a difference from how jupyter-lab treats math macros. You can define math macros in the frontmatter of a notebook (docs) at the moment. Tracking this here:

• Math Macros from Inline Equations mystmd#2388