Loaders: Use unique cache keys per loader type.

[Mugen87]

Fixed #27301.

Description

THREE.Cache is currently used by three core loaders: FileLoader, ImageLoader and ImageBitmapLoader.

Since the cache is global, loaders potentially share cache entries if the same URL is loaded by different loaders. Granted, that is an edge case but the OP of #27301 described a potential use case in #27301 (comment).

And since the cached results are incompatible between loaders anyway, it makes sense like described in #27301 (comment) to make the cache entries unique per loader. This is done by adding an additional loader-specific key part to the actual cache key.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	337.65 78.76	337.65 78.76	+0 B +0 B
WebGPU	557.6 154.28	557.6 154.28	+0 B +0 B
WebGPU Nodes	556.52 154.07	556.52 154.07	+0 B +0 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	468.89 113.45	468.89 113.45	+0 B +0 B
WebGPU	632.96 171.3	632.96 171.3	+0 B +0 B
WebGPU Nodes	588.01 160.61	588.01 160.61	+0 B +0 B

[mrdoob]

Hmm... Would it make sense to do this all the loaders instead? objloader:, gltfloader:, etc?

[Mugen87]

No other loaders are directly using THREE.Cache.

[Mugen87]

Ah wait..I see what you mean. Honoring the owner of the current file or image (bitmap) loader in the key instead of always using a name per loader type.

However, I'm not sure there is a benefit of doing this. I can understand if an image is loaded differently like described in #27301 (comment) but I don't think there is a use case for loading a glTF (or OBJ, FBX etc.) asset with a different kind of asset loader.

Besides, the "owner" information does not exists in the three basic loaders so we would need to pass additional name information from GLTFLoader or OBJLoader when creating file or image loaders.

[mrdoob]

Okay, sounds good to me!

Made some clean up: ee327fd ac07a8a