Allow mixins to describe custom elements

[justinfagnani]

Addresses feedback in runem/web-component-analyzer#157

[thepassle]

Should it still have a "superclass" field that has as value base here? Thats how I currently handle it in @custom-elements-manifest/analyzer, but it might be redundant I guess?

[justinfagnani]

No - mixins (usually) don't have superclasses until they are applied to a specific superclass.

When mixins do have a superclass, it's because of mixin composition:

const MixinA = (base) => class extends base {
  fieldA;
}

const MixinB = (base) class extends MixinA(base) {
  fieldB;
}

class C extends MixinB(S) {
}
const c = new C();
c.fieldA; // exists
c.fieldB; // exists

So here the superclass of MixinB would be MixinA.

[justinfagnani]

I added a short mention of this in the docs

[thepassle]

When a mixin has nested mixins, though, are those nested mixins then documented as being mixins, or superclasses? E.g.:

const MixinA = (base) => class extends base {
  fieldA;
}

const MixinB = (base) => class extends MixinA(base) {
  fieldB;
}

Would the mixin declaration look like this:

        {
          "kind": "mixin",
          "description": "",
          "name": "MixinB",
          "mixins": [
            {
              "name": "MixinA"
            }
          ],
         "parameters": [
             {
               "name": "base"
             }
           ],
          "members": ["//etc"]
        }

If we consider MixinA to be the superclass in that case, we have to change superclass to be superclasses and be an array, because there can be multiple mixins applied.

Intuitively, I feel like I'd prefer to name "nested mixins" just mixins in this case though

[justinfagnani]

That's a good point, I'll change the comments to says composed mixins should go in the mixins field.

[thepassle]

Im not sure I understand.

Given:

export const MixinA = base => class extends MixinB(base){}

Here the MixinB would be "superclass"?

What in the case of:

export const MixinA = base => class extends MixinC(MixinB(base)){}

?

[justinfagnani]

This was updated to say "a mixins should not have a superclass". In your examples the other mixins would be included in the mixins field of MixinA.

[thepassle]

I would still like to clarify this before merging #31 (comment)

[thepassle]

Hey @justinfagnani now that all the holidays are behind us, any chance we could pick up this discussion again? 🙂

[thepassle]

Nice, LGTM 👍