Debugging a syntax (or custom parsers)

[papler]

I was wondering how others debug a syntax, or when using a custom built parser (which might still be buggy). When the match is successful it's easy to output the tree to text, but if it fails, then it's hard to figure out how exactly the parsing was done and why it failed.

I added some additional code right into the Parser.cs, so I can enable outputting to console in real time. But I don't want to reinvent the wheel if there's already a better way to do it. Or I can share my solution.