rerender seems to update props instead of replacing them

[MysticEarth]

In a component we provide two inputs, avatar and name. Whenever avatar is undefined and a name is given, it should render the initials instead of an image. To test this behaviour we've used rerender:

rerender({ avatar: 'https://clipground.com/images/img_avatar-png-2.png' });

const renderedAvatar = screen.getByRole('img');

expect(renderedAvatar).toBeInTheDocument();
expect(renderedAvatar).toHaveAttribute('src', 'https://clipground.com/images/img_avatar-png-2.png');

...

rerender({ name: 'John Appleseed' });

// Initials should only exist if `avatar` is `undefined`
const renderedInitials = screen.getByText(/J/); 

(renderedInitials).toBeInTheDocument();

renderedAvatar succeeds as expected, but renderedInitials fails since avatar is still set – while I expected passing an object to rerender would completely replace all props.

The test succeeds when I explicitly set avatar:

rerender({ avatar: undefined, name: 'John Appleseed' });

// Initials should only exist if `avatar` is `undefined`
const renderedInitials = screen.getByText(/J/); 

(renderedInitials).toBeInTheDocument();

[timdeschryver]

Thanks for opening this issue @MysticEarth.
It seems like the other TL libraries are expecting like this, so we'll have to change our behavior.

The reason why it behaves like this, is to be able to test ngOnChange - which I think is valuable,
Because of this, I think the current render method should be renamed to change or update or something like that...

It would require a breaking change, so it could be a while before this lands.
Maybe with Angular v13...

[MysticEarth]

Ah yes, I understand! Sounds great you are introducing a new change method for this purpose.

[github-actions]

🎉 This issue has been resolved in version 11.0.0-beta.2 🎉

The release is available on:

• npm package (@beta dist-tag)
• GitHub release

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