$event->isValid = false not preventing saveUserPreferences call

[alexmglover]

Description

I have an event handler which hooks into User::EVENT_BEFORE_SAVE and is setting $event->isValid to false. I am getting an integrity constraint violation in MySQL because the user doesn't exist when attempting to create the user preferences entry.

This may be intentional behavior but I need to be able to stop the full creation of the user with that event handler. It does seem a bit like if Craft::$app->getElements()->saveElement($user, false) returns false, then an exception should be thrown and the transaction rolled back.

I'm attempting to halt execution and return custom JSON in the event handler, but this does not seem possible. Let me know if I am overlooking something.

Steps to reproduce

1. Create an event handler with User::EVENT_BEFORE_SAVE hook.
2. Attempt to stop execution with $event->isValid = false;

Additional info

• Craft version: 3.0.19
• PHP version: 7.1.19
• Database driver & version: MySQL 5.7
• Plugins & versions:

[brandonkelly]

Thanks! Fixed for the next release.