[Dancer-users] User-friendly errors on YAML parsing failures (was: Re: dancer croaking with a strange error in config.yml)

David Precious davidp at preshweb.co.uk
Mon Nov 14 17:27:39 CET 2011

On Monday 14 November 2011 16:16:29 Brian E. Lozier wrote:
> On Mon, Nov 14, 2011 at 8:11 AM, David Precious <davidp at preshweb.co.uk> 
> > Also, if the parsing failed, open config.yml and skim over it, and report
> > any lines which included tabs, with the line number.
> > 
> > This would be a fairly small amount of code, and would only come into
> > play if the parsing of config.yml failed (in which case, the app is
> > unlikely to start anyway, so it's not like it's extra complexity /
> > expense in the majority of cases).
> It seems like it would be better to contribute to the YAML module
> itself so it could report errors like this, as opposed to doing
> post-processing on an already-failed file.  

Hmm, yeah, that could make sense - although I think YAML.pm is to be replaced 
with essentially YAML::Any at some point.  Getting all the parsers to output a 
friendly message is likely harder than just outputting a fairly generic 
message ourselves.

We could have the message refer to an FAQ entry which lists various common 
mistakes in YAML for more details, perhaps.

> Also, aren't tabs allowed
> inside quoted values?  By the time you take into account all the valid
> possibilities, you will have rewritten a YAML parser.

Yeah, that's why I mentioned earlier in the message "look for any tabs in the 
file (before any non-whitespace chars)" - yes, tabs within quoted values 
should be valid, so I'd look only for e.g. /^\s*\t/ or similar.

Dave P

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