[main] No type information for elements, custom-elements

[NullVoxPopuli]

Example:

const ApplicationRoot: TOC<{ Element: null }> = <template>
  {{pageTitle "ExampleTsEmber"}}

  <custom-element />
    ^ hovering here: no type information
  <a></a>
   ^ hovering here: no type information
</template>;

export const Test: TOC<{}> = <template><ApplicationRoot /></template>;
                                        ^ hovering here: we see type information

now, it could be expected that custom-elements don't have type information, but the regular elements have known types, props, etc.

We also need a way to define custom-elements.

I briefly thought about the "loose mode" template registry:

declare module '@glint/environment-ember-loose/registry' {
  export default interface Registry extends PageTitle {
    'custom-element': ComponentLike<{ Element: HTMLDivElement }>;
  }
}

but:

1. I'm not using loose mode
2. custom-elements are not ComponentLike, so I'm not sure what I would provide for their type there

an example from @trusktr:

declare module 'whatever-framework' {
    interface WhateverInterface {
        'my-el': WhateverFrameworkElementAttributes<MyEl, MyElAttributes>
    }
}

maybe we can add this to support custom elements:

import { CustomElementLike } from '@glint/template';

declare module '@glint/core/custom-elements-registry' {
  export default interface Registry {
     'my-el': CustomElementLike<HTMLAnchorElement, MyAttributes>
  }
}

?

[LucasHillDex]

Hey @NullVoxPopuli do you think the best path here is to avoid using custom elements or do you think there might be a fix in the future? Considering v2 got rid of loose mode.

We have some custom elements that are actually web components, but others that were just used to decorate the markup unfortunately. However, considering it is valid HTML it does seem important to support somehow? Would it not be correct to say custom elements extend HTMLElement?

[NullVoxPopuli]

oh actually -- this is possible now -- I just need to document it.

if you do:

import '@glint/template';

declare global {
  interface GlintHtmlElementAttributesMap {
    'your-custom-element': {
      ['my-prop']: number;
      ['my-value']: string;
    } & GlobalHTMLAttributes;
  }
}

that should get you type-checking custom elements

[NullVoxPopuli]

actually, it does look like there is a bug -- I have a failing test in #1016 with the above declaration merge -- and I would expect that when throwing the type for your custom element in that interface that you'd get type-checking.

I'll fix this, standby

[NullVoxPopuli]

Fix is here #1016 -- just one failing bit left

Also adds docs for how to add the custom elements (WIP)