Keep in mind that you can't seek in FIFOs, and that the paths asserted to be files may be passed into other external utilities (such as during linting or unit testing).

I considered that case, but I think cases where seeking matters less. It may be better for me to implement a new function isReadableObject or the like which permits a FIFO, file, (or even others) and use it instead.

It is certainly correct for me up to update the documentation in either case.

I'll leave it up to @epriestley which he prefers, and I'll do that