Does Wielder of Water's 'while I attack' ability trigger before or after Ahri's 'when you attack' ability?

Ruling: 'While' is a passive effect, not a triggered effect. Wielder of Water will already be a +2 before Ahri's effect is added to the chain.

Nuances:

• 'While' abilities are passive and apply immediately during the relevant game state
• 'When' abilities are triggered effects that use the chain