Polearm Master/Sentinel/War Caster Glavelock question.

[Swimbley]

What happens when you cast the infestation cantrip as your reaction with a polearm.

For PA, the attack comes in, spell goes off, failed save. Then the attack is just interrupted? Same question for sentinel, attack comes in, spell goes off, failed save, movement is 0, but the spell indicates at least “5” is granted. Conflict? Do they move 5 feet, before the attack?

[1Pirate]

Not quite sure you articulated that correctly. You either attack or you cast the spell as an OA. You don’t do both.

[LudicSavant]

You get a spell or an attack. Not both.