Does Eerie Spell still reduce PP if it has no effect?

Question

If Eerie spell is used on a dark type, will it still reduce the PP of the move?

Answer 1

No, it doesn't.

Check my replay. Absol used Sucker Punch, Slowking used Eerie Spell on it. Sucker Punch remained at 7 PP, and Absol was shown to be immune to the move entirely.

Hope I helped!