title: Conditionally prevent from value to change in mat-select
body: <p>When user tries to select another value in mat-select I want to show popup to confirm if user indeed wants to select another value. The problem in time I show popup visually the selected value is already presented in the mat-select. Can I somehow prevent this value to change until user decides to select? <a href="https://stackblitz.com/edit/angular-2alu7b?file=src%2Fapp%2Fapp.component.html" rel="nofollow noreferrer">Here is an example code</a></p>