Add closePredicate option to dialog

[crisbeto]

Adds the closePredicate config option to the CDK and Material dialogs that allows developers to programmatically determine whether the user is allowed to close a dialog.

[crisbeto]

I'm somewhat on the fence about this API, because technically you can do the same by combining existing APIs and being careful with your event handlers, but I decided to implement it since there's clearly demand for it in #14292 and it can be easy for users to mess up if they do it themselves.

There's an overlap with disableClose and initially my thought was to change disableClose to also accept a function, but the problem is that it only applies to attempts at closing the dialog using the backdrop or the escape key, not programmatic closes or by something like the matDialogClose directive.

[jelbourn]

I'm also iffy about this API.

• It's typically an a11y issue to prevent dialogs from closing on escape/outside click; this might encourage more of that
• The name could be misleading, because what we're really doing is something like disableCloseFromUserInteractionPredicate. That is, it doesn't prevent closing via API call . This is especially confusing with matDialogClose.

I know the current disableClose also has these issues- I'd be more inclined to rename that to simplify this (something like disableCloseOnInteraction or disableDefaultCloseActions)

[crisbeto]

The idea with the new API is that it blocks all the close calls, even the programmatic ones, whereas disableClose was only for the backdrop and escape keys. The primary use case for this is if you have a form and you want to prevent the user from accidentally closing it based on a certain condition.

[jelbourn]

I can be on board with this if we rename disableClose to avoid confusion between the two (deprecating the current name for the appropriate time)

[aldovelasco-acme]

I'm interested in this feature. Would this new API block the modal from being closed if matDialog.closeAll() was called?

[JonasDev17]

any update on this?

[crisbeto]

Closing in favor of #30919.

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