Does enrage trigger if a creature with enrage is dealt 0 damage?

Enrage is a triggered ability that reads "Whenever [this creature] is dealt damage..." For enrage to trigger, the creature must actually be dealt damage — a positive amount. This is grounded in CR 119.2, which states that objects that deal 0 damage deal no damage at all.

CR 119.2 is explicit: if an effect would deal 0 damage, it does not count as dealing damage. This means no damage event occurs, and any ability that triggers on being dealt damage — including enrage — will not see a trigger condition being met.

This matters in situations where a creature's toughness, prevention effects, or replacement effects reduce damage to 0. For example, if a creature with a Shield counter (which prevents the next damage it would take) would be dealt 2 damage, the Shield counter reduces that to 0 — no damage is dealt, and enrage does not trigger.

Concrete example: Your opponent attacks with a 2/2 and you block with your Polyraptor (which has enrage). If Polyraptor has a damage-prevention effect that prevents all damage this turn, the 2 damage becomes 0, no damage is dealt, and Polyraptor's enrage ability does not trigger.

By contrast, if even 1 damage gets through (after prevention), that counts as damage being dealt and enrage will trigger normally (CR 702.77, the enrage rule introduced in Ixalan).