bug(dialog): Typing of new `MatDialogConfig.closePredicate`

[PowerKiKi]

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

#30919 introduced the new MatDialog config closePredicate. I am struggling to make typing work to have a 100% typed code.

Reproduction

StackBlitz link: https://stackblitz.com/edit/9wtzaa17?file=src%2Fmain.ts

Steps to reproduce:

1. open link, it does not compile, but I expect to compile

Expected Behavior

At first I expected that types would be flowing, so that I wouldn't need to repeat them. So my expected usage would be like:

this.dialog.open<MyDialog, MyDialogData, MyDialogResult>(
  MyDialog,
  {
    closePredicate: (
      result,
      config,
      componentInstance
    ) => {
      return something();
    },
  }
);

But that failed to compile. So I tried to add typing like so:

this.dialog.open<MyDialog, MyDialogData, MyDialogResult>(
  MyDialog,
  {
    closePredicate: (
      result: MyDialogResult | undefined,
      config: MatDialogConfig<MyDialogData>,
      componentInstance: MyDialog | null
    ) => {
      return componentInstance?.animal() !== 'my original data';
    },
  }
);

That also fail to compile. And I am out of ideas.

Angular Material source never use this callback with any parameters (neither in implementation, nor in tests).

What is the expected usage pattern here ? Is there a way to avoid repetition ?

Actual Behavior

Stackblitz does not compile

Environment

• Angular: 20.1
• CDK/Material: 20.1
• Browser(s): Chrome
• TypeScript: 5.8.3

[ok7sai]

I might be wrong but I don't think there's a way to assign type generics within a parameter. You can do type casting in the callback function instead https://stackblitz.com/edit/9wtzaa17-m8hxdy56?file=src%2Fmain.ts. Since the component type is unknown | null, you can cast it to MyDialog | null.

[PowerKiKi]

I think you are right that casting is the only way, but that feels dirty, especially in a recently introduced API like this one. I suggested the start of a possible solution in #31892 ...