fix(selection-model): inaccurate selected value when accessed in change subscription

[crisbeto]

Fixes the selected value being out of date in the SelectionModel, if it is accessed inside an onChange subscription.

Fixes #8584.

[jelbourn]

LGTM

[simeyla]

Any chance of ever add selected to the interface?

 export declare class SelectionChange<T> {
     added: T[] | undefined;
     removed: T[] | undefined;
     selected: T[] | undefined;
     constructor(added?: T[] | undefined, removed?: T[] | undefined);
 }

I realize it's a change event, but as a convenience it would be very handy.

Edit: I see now why that would be inefficient. The _selected array isn't up to date when the change event is emitted so you wouldn't want to run through the whole array just to raise the change event.

[crisbeto]

@simeyla the intention with the selected is that we try to avoid recomputing it until it is requested. That being said, I think that we can expose the SelectionModel, that triggered the event, for convenience which will allow you to get the selected value without having to reach outside the function.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}