We need the ability to deregister or undefine custom elements.

[johngamble]

There have been a couple of previous tickets created about this but they have been closed:
webcomponents/webcomponents.org#1294
#754

This is another use case which has not been brought up before, but an important one.

During unit tests, if we are unable to clean up and reset the browser state, then you break all future unit tests.

Please see my Stack Overflow post for a detailed explanation of the problem:
https://stackoverflow.com/questions/73849002/unit-tests-of-angular-elements-registered-with-the-customelementregistry-as-a-h

Custom elements are a very powerful feature, but not being able to write tests for using them really undermines their adoption.

[rniwa]

Why can't you create a new iframe for each unit test? That's exactly what I do in my own UI framework / library, and it works great.

[sashafirsov]

ability to de-register the custom element would allow to incrementally inherit currently registered element with own implementation which would use the original:

• my-component is served by class MyComponent
• taking the class from registry
• register my-component-internal with MyComponent
• unregister my-component and register class MyComponentFacade to same tag
• use my-component-internal from overridden my-component-internal

there are zillions of use cases. From translation to analytics. Facade pattern is quite useful in general. Without unregistering the custom tag generic AOP approach would be difficult in Web Components world.

[caridy]

sounds like a duplicated of #754

[rniwa]

Indeed. Closing as a duplicate of the issue #754

[johngamble]

Why close this issue if #754 has been closed? We need one of these tickets to be left open so it will actually be addressed?

[rniwa]

Please refer to #754 (comment) as how this issue can be re-opened.

[sashafirsov]

@rniwa , not here nor in #754 there is no clear criteria of reopening. The reference to the scoped element registry is orthogonal as it has same issue with undefining/redefining custom elements as global here.

Would be nice to answer on what could be the basis for issue reopening.