Since there's no way that option can ever do anything. pattern needs to be set before rspec loads any files (so that RSpec knows which files to load), and since RSpec.configure gets called in one of the pattern-matched loaded files (or, more typically from a file required by one of those files, such as spec_helper), it's too late to change pattern at that point. Thus, it's confusing for pattern to be an available option from `RSpec.configure.
For more background on this, see #682.
I'd like to pick this one up over the weekend. Dibs!
@myronmarston it can be though, because a 3rd-party gem could configure pattern in this way before loading the specs.
@JonRowe -- good point. Maybe we should just warn that the option has no affect if it is set after RSpec has started loading the specs?
Are you suggesting substituting a method on the configuration instance which spits out the warning, or just warning every time?
I'm suggesting changing the method on the configuration instance such that it conditionally warns based on whether or not RSpec has already started loading the spec files.