Fix #105, allow trailing commas in query macros

[tim-harding]

Fixes #105

[abonander]

Looking good! I'd like to have this tested for query_file!() and query_file_as!() as well; I think we're fine with the doctests covering the case of no-trailing-comma.

[tim-harding]

Sounds good. I was also curious about your comment on another thread about not using $(,)? because it introduces a metavariable. Are there compiler performance downsides to unused metavariables or some other reason you don't prefer that approach?

[abonander]

Okay, so $(,)? does work in the matcher for parsing; the mistake I made was for some reason I wanted to pass that trailing comma to the inner macro since it may accept them, but besides the fact that would be completely pointless, there's no way to capture that extra comma in the expansion because it's not bound to a metavariable. Basically I just had a brainfart. You can absolutely just use $(,)? to permit an optional trailing comma without having to introduce an extra matcher to the macro.

[abonander]

@timmythetiny did you want to do the above simplification? Sorry for overcomplicating things before.

[tim-harding]

I'll get to it tonight. Sorry for the delay.

[abonander]

No worries, I just wanted to make sure you were still interested. I was tempted to just do it myself, but I would have merged this anyway so you got the contributor credit.

[tim-harding]

Reasonable enough. It was a very easy change.

[abonander]

Perfect!