What is the common law principle of discoverability?

Prior to the Act incorporating s. 8(2) the common law principle of discoverability was well settled. The discoverability principle, as set out by LeDain, J. in Central & Eastern Trust v. Rafuse, 1986 CanLII 29 (SCC), 1986 CarswellNS 40 (SCC), was referenced in Barry v. Halifax Regional Municipality, 2017 NSSC 180. A cause of action arises for purposes of a limitation period when the material facts on which it is based have been discovered or ought to have been discovered by the plaintiff by the exercise of reasonable diligence.