A few weeks ago, I implemented syntax highlighting for markdown in aretext, the minimalist vim clone I’ve been building. Like most context-sensitive languages, markdown is difficult to parse. Although it handles only a subset of the CommonMark 0.30 spec,1 my implementation required 845 lines of Go code. Parsing is especially tricky because the code needs to handle any document a user might open. It can’t crash or enter an infinite loop.
