This change adds a feature needed for aspnet/Mvc#302
There's a new option in routing that allows link-generation to proceed
when the route values cannot be validated. The key scenario for this is
during development of an MVC site. Routing will refuse to generate a link
to actions which don't exists, this is a breaking change from the MVC5
behavior. Setting UseBestEffortLinkGeneration will allow routing to return
a value even when we can't match the action.
This option will remain off by default - setting this to on will impact
link-generation in a bunch of scenarios involving areas where we've
improved the logic for MVC6. If you're considering leaving this on outside
of development scenarios, then make sure to be as explicit with route values
as possible (don't rely on ambient values).
Functional tests to follow up in the MVC repo.
Mugdha Kulkarni
Ryan Nowak
Harsh Gupta