bug(mat-stepper): Undocumented breaking change in Angular 20

[Sergiobop]

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

19

Description

Previously to Angular 20 we could customize the stepper header to hide icons with this workaround:

@ViewChild(MatHorizontalStepper) stepper: MatHorizontalStepper;

ngAfterViewInit() {
  this.stepper._getIndicatorType = () => 'number';
}

Now, in Angular 20, we can't, since the method was removed in c8f942d

How can we customize the indicator type now? It should be an input. Thanks!

Related:
#10513
#18307

Reproduction

StackBlitz link:
Steps to reproduce:

1. Try to customize the stepper like we did before
   2: ✘ [ERROR] TS2339: Property '_getIndicatorType' does not exist on type 'MatStepper'. [plugin angular-compiler]

Expected Behavior

Input to customize the indicatorType

Actual Behavior

IndicatorType is not customizable anymore

Environment

• Angular: 20.1
• CDK/Material: 20.1

[andrewseguin]

The underscore before the API name is an indication that it is internal-only and not part of the public API. You are welcome to open a feature request for what you want from the stepper