This repo shows the problem with ExDoc and an external library such
as KaTeX. Look at the mix.exs file to see how
KaTeX was set up using the before_closing_head_tag.
The bug was introduced in ExDoc 0.28.6 (i.e., 0.28.5 works). Build the docs
(i.e., mix docs) and then open doc/index.html in the browser. The math is displayed in
both cases, but in ExDoc 0.28.5 the modules are shown in the left-hand pane,
but not in 0.28.6. Open up the JS console in the browser to see the error
when doing a hard reload of the page. For some reason, with 0.28.6 onwards the
HTML element with the ID toast is not present at the time the module pane is
being rendered.
The fix is in the commit:
https://github.com/woodward/ex_doc/commit/a5ed367990315271eede9c67e83c922df7d6bd27
Basically, only add the event listener to the HTML element with the toast ID if
it exists in the page.
You can try out various versions of ex_doc (see the deps section of the mix file); just
be sure and clear things out between runs of mix docs! e.g., delete doc/*, _build,
and make sure you update the deps to the correct version.