bug(mat-date-range-input): formGroup error doesn't switch form field error state

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

Hello,

https://material.angular.io/components/datepicker/overview#date-range-input-forms-integration
The mat date range input documentation states:

Date range input forms integration

The mat-date-range-input component can be used together with the FormGroup directive from @angular/forms to group the start and end values together and to validate them as a group.

So I'm expecting the form group, grouping start and end date, to update the "global range input" state, but this is not the case.

My use case is to add a customValidator (to limit the number of days between start and end dates) on the formGroup. When the form is in error, I was expecting the form field to be red and to display mat-error, but nothing shows when the form is invalid.

• Is it a bug?
• Is it the normal behavior, and a documentation ambiguity? It would be a nice new feature in this case.

I've found a workaround using ErrorStateMatcher. But it feels like it's supposed to be included in mat date range picker as both inputs are inside, within the formGroup
https://material.angular.io/components/input/overview#changing-when-error-messages-are-shown

Reproduction

Have mat date range picker with a form group validator => only start and end controls are updating displayed form field validity

Reproduction link: https://stackblitz.com/edit/stackblitz-starters-xhx4k1?file=src%2Fmain.ts

Expected Behavior

When formGroup is in error, form field state should be in error and display mat-error

Actual Behavior

When formGroup is in error, form field state is valid and no mat-error is displayed

Environment

• Angular: 18
• CDK/Material: 18

打开链接的 StackBlitz 复现，并先阅读 date-range input forms 集成文档。跟踪 form-group validator 如何影响 date-range 字段的错误状态；当无效组将字段标记为错误并显示 mat-error，而有效组保持不变时，即表示完成。