What is the limitation period for an action against an attorney for a wrongful act or omission?

Code of Civil Procedure section 340.6, subdivision (a), provides "[a]n action against an attorney for a wrongful act or omission, other than for actual fraud, arising in the performance of professional services shall be commenced within one year after the plaintiff discovers, or through the use of reasonable diligence should have discovered, the facts constituting the wrongful act or omission, or four years from the date of the wrongful act or omission, whichever occurs first." The section "states 'two distinct and alternative limitation periods: one year after actual or constructive discovery, or four years after occurrence (the date of the wrongful act or omission), whichever occurs first.' [Citations.]" (Samuels v. Mix (1999) 22 Cal.4th 1, 7.)