One of my players uses the Plane Shift spell quite regularly in battle to get rid of unwanted opponents. With the ready action and the holding of a spell being a thing, the question has come up, whether he could ready the Plane Shift spell as an action and wait for the opponent to attack him as the trigger to release the spell.
You can use this spell to banish an unwilling creature to another plane. Choose a creature within your reach and make a melee spell attack against it. On a hit, the creature must make a Charisma saving throw. If the creature fails this save, it is transported to a random location on the plane of existence you specify.
The question that came up is whether he would still have to make a melee spell attack as described in this part of the spell. The reasoning of my player is, that if a dragon bites him, he is technically already touching him or he could simply reach out to "boop the dragon's snoot" since he has his teeth sunk into his arm and therefore cannot really dodge his hand.
The first time he did this I let it slide per "Well, guess you outsmarted me this time. Sure go for it" - but I feel like in the long run it might be a bit tricky to have a player forego a part of the spell. It doesn't seem to me that this is how it is intended. A fighter would also still have to roll if he can hit the target, but at the same time Plane Shift is still connected to a Charisma Saving Throw the target has to fail so I am unsure how to handle it per RAW/ RAI.