[mat-dialog-close] button is called many times without even clicking the button itself.

[anisabboud]

Bug:

[mat-dialog-close] button is called many times without even clicking the button itself.

What is the expected behavior?

[mat-dialog-close] button should be called only when clicked.

What are the steps to reproduce?

1. Go to: https://material.angular.io/components/dialog/examples and
   click the "Edit in StackBlitz" icon button.
2. Open dialog-overview-example-dialog.html and
   replace [mat-dialog-close]="data.animal" with [mat-dialog-close]="submit()"
3. Add submit() { console.log('submit()'); } to the bottom of dialog-overview-example.ts
4. Click "Open in New Window" ⇒ https://emgagvlolxy.angular.stackblitz.io/
5. Click the button to open the dialog, and check the console:
   submit() was called 8 times without clicking the button!
   Any interaction with the dialog calls it many times more.
   (E.g., typing "dog" in the textbox calls submit() 16 more times.)

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Angular 5.1.3
Angular Material 5.0.2

[crisbeto]

The mat-dialog-close input is for passing in the result with which to close the dialog. It will be evaluated on every change detection cycle.

[anisabboud]

Thanks for the details, @crisbeto.
I don't understand why it has to be evaluated on every cycle instead of once when the dialog is actually closed...
It sounds inefficient, especially if the submit() function is not trivial.
It could also cause a crash when the submit() function assumes the data is valid (the user clicked the submit button that is enabled only if the form is valid).

[crisbeto]

That's how data binding works in most frameworks, which is also why you should avoid binding very intensive functions to your view.

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