ah ok, for core symfony, this is part of the {_format} pattern. 

in RouteProvider::getCandidates, we eat away the format, which means i can not have different routes for different formats. this seems wrong to me. imo we should make two candidates, first one with the format and then another one without. to capture the format, the route should spell out {_format} at the end of its variablePattern part. if its a route for one specific format, this would become tricky however, as there the explicit format is already part of the static part of the pattern. the route could play around with itself and translate `.xy` into the default and requirement for _format and replace that part of its path with {_format}

if we would do those things, we would need no more magic in the route provider i think. it feels odd what we currently do.
@lsmith77 do you agree that the goal in the end is:

* if the route does care about _format at all, the route match has to have the format in the resolution parameters
* if the route ends with .format this should be interpreted as _format
* what does core symfony do about _format if nothing is said explicitly? is it then available anyways?

i can create functional test cases about the format and once we agree what should happen try to refactor the magic.