Bootstrap validation conflicts

In a nutshell, remove novalidate from <form> in your Vue template. When you set novalidate, the inputs will remain in their :valid state throughout their lifecycle until you explicitly call setCustomValidity. Working Sandbox

Since, Bootstrap styles also apply to :valid or :invalid states so, even if your custom validators determine inputs to be invalid, both valid and invalid styles will get applied i.e. :valid and .is-invalid but, I guess it's just happens so, that :valid styles take precedence the way Bootstrap stylesheet is currently written.

U̶s̶e̶ ̶̶n̶o̶v̶a̶l̶i̶d̶a̶t̶e̶̶ ̶w̶h̶e̶n̶ ̶y̶o̶u̶'̶r̶e̶ ̶i̶m̶p̶l̶e̶m̶e̶n̶t̶i̶n̶g̶ ̶a̶ ̶c̶o̶m̶p̶l̶e̶t̶e̶ ̶v̶a̶l̶i̶d̶a̶t̶i̶o̶n̶ ̶s̶o̶l̶u̶t̶i̶o̶n̶ ̶y̶o̶u̶r̶s̶e̶l̶f̶ ̶i̶n̶c̶l̶u̶d̶i̶n̶g̶ ̶̶r̶e̶q̶u̶i̶r̶e̶d̶̶ ̶v̶a̶l̶i̶d̶a̶t̶o̶r̶.̶

With Bootstrap, since it also applies styles to :valid or :invalid states of input, you're better off NOT using novalidate.

Ofcourse, this will enable browser popups asking for filling certain fields which might be unwanted.

Suggestion: Use validated prop on your form and bind it to your form's state and set it to true in addReview(), it will automatically add was-validated class and you don't need to manipulate the DOM directly.

EDIT: Since removing novalidate enables browser validation, submit event no longer fired on the form and hence, was-validated class is never added to the form. This presented an issue in my original answer because messages and icon were not shown without was-validated. I have modified the sandbox to suggest a fix for that and that is to bind click event to submit button for validation logic and using submit event for stuff that should happen after successful validation.

EDIT for Datepicker: The reason why datepicker never invalidated was because of an issue in isStateValid() method specifically the part:

if(variable) { // "" evaluates to false   // ...}

Since "" evaluates to false, it will always return null. The fix for that is in combination with the suggestion above of maintaining validated state for the form. Now, instead of checking if(variable), we check if(this.validated) and if it is true, we simply check the length and return either true or false.

1. Fundamentally was-validated is not bootstrap-vue native, it's browser native, which also has no understanding of :state. If you want to use was-validated you can't use custom validations. If you want to use custom validations. See the suggestion For 2. Which is basically, use another variable to control whether validation should be applied.

2. From the documentation on bootstrap-vue

When set, adds the aria-required="true" attribute on the component. Required validation needs to be handled by your application

You need to explicitly check that the validation should show, it isn't clear from the documentation what required actually does, but it doesn't affect validation. Which explains why that part isn't working. Personally I set a global this.showValidations = true on submit, so that the validations actually run at the right time and not before (and after when expected). In your case, you can check for the was-validated class that you are adding explicitly. It isn't great, but it seems it must be done here.