`net9.0`: `@Assets` support

[linkdotnet]

Withb net9.0 ComponentBase has a new Assets property to load static mapped asset files (mainly CSS and javascript files). But they user could also load other assets like media files.

In its core, those properties are retrieved from the Renderer.

We might wanna invest some time to offer a way for users to fill up the collection with entries.

PS: I don't see this as a high-priority enhancement, but still worth time spending.

[egil]

What is the test scenario?

[linkdotnet]

If users have logic like such:

<img src="@Assets[imgSrc]" />
@code {
   private string imgSrc;

   protected override void OnInitialized() => imgSrc = GetDataAssetPathFromSomewhereDynamic();
}

Given that "imgSrc" is somewhat of a detail, the user properly asserts against the markup. The markup (more precise: the src value for the img tag) will be empty, as no one is "filling" this dictionary (or even fails, I did not check how bUnit currently behaves).

[linkdotnet]

Here the current behavior of bUnit - given the following component:

@{
#if NET9_0_OR_GREATER
}
<img src="@Assets["img.png"]" />
@{
#endif
}

And a test like this:

[Fact(DisplayName = "Renders an asset path")]
public void Test001()
{
	var cut = RenderComponent<AssetsComponent>();

	var img = cut.Find("img") as IHtmlImageElement;
	img.ShouldNotBeNull();
	img.Source.ShouldNotBeEmpty();
}

Then img.Source is "about:///img.png"

EDIT: The Markup seems "fine":

<img src="img.png" />

[linkdotnet]

Maybe that is then "good enough" and we can close the ticket. For sure we shouldn't add any magic

[LasseHerget]

Reopened in #1846