An unlicensed person performs work requiring a license and sues the customer for nonpayment. What is the result?

解析

B&P §7031(a) bars a person from bringing or maintaining any action for the collection of compensation for work requiring a license without alleging licensure at all times during performance, and it says so 'regardless of the merits of the cause of action'; §7031(b) goes further and lets the customer recover back what was already paid. (a), (b) and (c) are the equitable compromises the courts have refused — no discounted contract price, no cost recovery, no restitution in quantum meruit. The one narrow escape is the substantial-compliance showing under §7031(e).