[WIP] [BUGFIX beta] Support concatenatedProperties in contextual components

[Serabe]

Given a component my-comp with a concatenatedProperties: ['foo'] this:

{{component (component (component "my-comp" foo=1) foo=2)}}

should produce foo: [1, 2] (unless there are other values in the class, then
those values would be concatenated as well).

This is not happening due to curryArgs does not take into account the
concatenatedProperties and mergedProperties properties. One of the problems
with current implementation is that these properties work at mixin level, thus
making them only accessible working out the proto (see emberjs/rfcs#209 for
more details.

This initial draft does not fully work. For this to continue I need to know
some details:

1. Is there an implemented way in glimmer to create an Reference that is
   a collection of reference? I need to concatenate two references/array of
   references into an array.
2. Is the proto method expensive enough not to continue?

[homu]

☔ The latest upstream changes (presumably #15014) made this pull request unmergeable. Please resolve the merge conflicts.

[AnastasiyaYelets]

@Serabe hey, why did this pull close? Issue still not fixed in ember

[Serabe]

I can try to give this another try, the thing was supporting this is (or at least was) pretty expensive and nobody had requested it in over two years. We can try and give it another go.

[KirillSuhodolov]

@Serabe I founded similar issue #14914

I am trying to have merged properties that passing via component

{{component (component (component "my-comp" foo=(hash a=2)) foo=(hash b=3))}}

foo defined as merged property at component

looks at codebase it not implemented at ember-glimmer component helpers

[Serabe]

Yes, I know. The problem with concatenatedProperties and mergedProperties is that they are instance properties, and therefore would require creating an instance of the component to know its value.

[KirillSuhodolov]

so, at such example will be create two extra waste components at runtime?

[Serabe]

Yes.

[KirillSuhodolov]

@Serabe anyway, is it possible add to ember?

[Serabe]

@AnastasiyaYelets @KirillSuhodolov this won't be fixed. This feature would be pretty expensive computationally and had some undesired side-effects from initialising the component each time.

Please, for anyone reading this, the behaviour that won't be fixed is not that concatenated properties won't work if a component is invoked as a contextual component, but that concatenated properties work in nested contextual components. Let me show this with an example:

{{! this won't concatenate properties }}

{{#with (component "my-component" classNames="first-declaration") as |comp|}}
  {{#with (component comp classNames="second-declaration") as |nestedComp|}}
    {{component nestedComp}}
  {{/with}}
{{/with}}

second-declaration is overwriting first-declaration as value. This ember twiddle shows the behaviour with a few classes.

Thank you!