feat(MatSelectionList): MatSelectionListChange options should contain automatically deselected values

[mcalmus]

Is this a regression?

• [ ] Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

When using a MatSelectionList with multiple select mode off, selecting an item deselects the previously-selected item. If listening to changes, the options property of MatSelectionListChange only has the newly-selected value, not the previously selected value. The documentation indicates it should contain "changed" items. The one that was deselected should therefore be included.

Reproduction

Steps to reproduce:

1. https://stackblitz.com/edit/angular-wqdcyq?file=src%2Fapp%2Flist-single-selection-example.ts
2. Select an option - change count increases by one
3. Select a different option - change count (and log) only shows one item rather than two

Expected Behavior

Change count after selecting a new item should increase by 2.

Actual Behavior

Change count only increases by one

Environment

• Angular: 15 (also occurs in 14)
• CDK/Material: 15 (also occurs in 14)
• Browser(s): all
• Operating System (e.g. Windows, macOS, Ubuntu): all

[mmalerba]

Can you give more info about the use case you have in mind for this? I'm not sure this really makes sense for single selection, as selecting an item always implies all other options are unselected.

[mcalmus]

I would like to use a single change method for several components to audit changes. Once the change has fired there is no way to get the previous value.