[NTG-context] Parsing ConTeXt errors

Hello, I'm trying to parse ConTeXt errors. TeX and Lua errors seem easy to parse (search for 'tex error' and 'lua error', respectively), but I have a couple of problems with MetaPost messages. First, when there are MetaPost errors, context/mtxrun exits with a zero exit code. Is that intentional? Second, as far as I see, there is no way to locate the error in the source from the log. I can only retrieve the file causing the error (by searching for an 'open source' line - very useful, btw), but no line number. Am I missing something? I think it would be very useful to have at least an approximate indication of the position of a MetaPost error. Nicola