I have implemented parsing math inline of $...$ and $$...$$ and I followed mostly how parsing is done for emphasis delimiters, but I’m not really convinced this is the best way to do it. I would in fact expect $...$ and $$....$$ to work a bit like a string with quotes (but would just allow escape with \$).
But looking at pandoc for example, with the following case:
This is a test $$this is a test$
it is generating this:
<p>This is a test <span class="math inline">\($this is a test\)</span></p>
Unlike delimiters, I would expect that a $$ should match an ending $$
I’m not sure how Latex behaves with this. Is this the way it is usually handled?