Line numbers in errors

[schneems]

Right now, when something fails we cannot point to where in the original document triggered that command. This is due in part because we use parselet to parse the commands inside of blocks, but regex-es to find the blocks.

I'm anticipating moving away from regexes and towards parsing to find the code blocks. But that's an orthogonal goal.

If we could even say "the problem happened somewhere in this codeblock" that would be a huge quality of life improvement.

The code that handles "code sections" is ... not good. You could call it "tech debt" even. When I wrote this, I didn't know how the outcome would look now that the project is more stable, we could refactor some of that into something cleaner. Again, this is orthogonal to the original issue...but I'm open to it if it helps us achieve a better error experience.