Spells and TWF

[Nullmancer]

The rules state that if you swing with a light melee weapon, you can use your bonus action to swing with another similar weapon. What would you guys say if a cleric cast a spell that used an attack action, did not take up a full turn, and allowed you to use a bonus action? Could you, per say, cast a spell and attack with a dagger in your other hand?

[JumboWheat01]

Spells don't use the Attack Action. They use the "Cast a Spell" Action. So no, I wouldn't say casting and then attacking with an off-hand weapon is allowed.

[zylodrizzt]

Maybe with booming blade or green flame blade cantrips. I can see how it could be interpreted that way and I don't think it would break the game either. And before it's asked no your twf attack cannot be one of those cantrips

[Demonic Spoon]

Maybe with booming blade or green flame blade cantrips. I can see how it could be interpreted that way and I don't think it would break the game either. And before it's asked no your twf attack cannot be one of those cantrips

It cannot be interpreted that way, except very incorrectly. Taking the attack action and making a single weapon attack are very different things, and the rules depend on that distinction in many different places.