Quote Originally Posted by Rukelnikov View Post
Tbh, I disagree, it may be an unpopular opinion, but Shield Master requires you to take the Attack action in order to get the shield bash as a BA, if for whatever reason you are prevented from taking the action later on then you shouldn't have been able to perform the bash.
Let 'em take it before the attack action. I'm fine with trying it to the attack action, but it should be able to be taken prior to rolling the attack.

"When you take the attack action, prior to rolling the attack, you can attempt to shove as a bonus action."

Works for me.