bug(mat-autocomplete): missing selection indicator (highlight + check icon) when using mat-autocomplete with mat-optgroup

[poveu]

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

14

Description

v15 introduced an indicator of the currently selected item:

However, this indicator is missing when, instead of flat mat-options, we're using mat-optgroup with mat-options:

Reproduction

The repro is even in the official documentation of any version higher than v14:
https://v15.material.angular.io/components/autocomplete/examples

Expected Behavior

We should see the indicator of a selected item even when we're using mat-optgroup

Actual Behavior

Missing selection indicator when using mat-autocomplete with mat-optgroup

Environment

• Angular: v15+
• CDK/Material: v15+

[amysorto]

Tested in v18, also still occurs