No convenient way to set default assets through the `AssetServer`

[SludgePhD]

What problem does this solve or what need does it fill?

Currently, it seems like the simplest way to set the default value of an Assets collection is this:

fn load_default_font(mut fonts: ResMut<Assets<Font>>) {
    let bytes = include_bytes!("font.ttf");
    let font = Font::try_from_bytes(bytes.to_vec()).unwrap();

    fonts.insert(AssetId::<Font>::DEFAULT_UUID, font);
}

This sidesteps the whole asset system, and requires including potentially large data in the binary (in my case, a 14 MiB font file), so it's not ideal.

AssetServer has no methods that load an asset into an existing Handle/AssetId, so it cannot directly be used for this. It's possible to load the asset with a different Handle, listen to the asset event that indicates it has loaded, and then copy the asset over to the default ID. This is extremely inconvenient, though.

What solution would you like?

AssetServer should expose some way of asynchronously loading an asset into an existing Handle or AssetId, overwriting whatever is already there.

What alternative(s) have you considered?

None so far. Open to suggestions.

[rparrett]

It's possible to load the asset with a different Handle, listen to the asset event that indicates it has loaded, and then copy the asset over to the default ID. This is extremely inconvenient, though.

Just linking up an example of this sort of method for illustration: #8445 (comment).