Asset loading on the Web produces many 404 errors for .meta files

[coreh]

Bevy version

5733d24

What you did

Ran any example that loads assets under WASM / WebGL with:

cargo run -p build-wasm-example -- $EXAMPLE_NAME_HERE && python3 -m http.server --directory examples
/wasm

What went wrong

Got barraged with 404 error messages in the web inspector with the page trying to load .meta files for every asset loaded.

Additional information

• Looks like with Bevy Asset V2 #8624 we now look for .meta files for every asset that we load
• On native this is a non issue, however on the web we do a bunch of requests, which both spam the console with 404 errors and also potentially slow down loading of the files that actually exist

[hymm]

A solution might be for the web asset source to write out a manifest file of the available asset files. This could also be used to solve load_folder not working on the web.

[mockersf]

Adding the 0.12 milestone. I think this should be looked over before the release, it will raise a lot of questions on wasm

[hymm]

Should probably just suppress the error message on wasm for now, until we come up with something better.

[alice-i-cecile]

No PR exists, and the release is imminent. Bumping to 0.13, but I'd nominate this for 0.12.1 as well.

[rparrett]

Adding this info for searchability.

This is also tripping up users who are using trunk or other dev web servers that act in an "SPA" mode where the server doesn't actually serve 404s.

They will see error messages like

/home/redacted/.cargo/registry/src/index.crates.io-6f17d22bba15001f/bevy_asset-0.12.0/src/server/mod.rs:274 Failed to deserialize meta for asset image.png: Failed to deserialize minimal asset meta: SpannedError { code: ExpectedNamedStructLike("AssetMetaMinimal"), position: Position { line: 1, col: 1 } }

Because the web server is just serving the contents of index.html with a status of 200 when a file is missing.

[forbjok]

When uploaded to itch.io, the server the assets are hosted on return 403 instead of 404, and this actually causes the game to completely fail to run.

[alice-i-cecile]

If we can get a fix in for this, we should include it in 0.12.1

[rparrett]

Is there a procedure users can follow right now to generate default meta files to work around the issue on itch?

edit: Here is something that seems to work:

• Enable processing temporarily.

• Run your app once. It will generate meta files in the assets directory.

• (bug?) Bevy attempts to load the meta files without the assets subdirectory in the path. This is true when in either AssetMode. So you need to move the meta files one directory up in the hierarchy.
  (edit: yes, bug, will be fixed later by #10527)

  That is, if your assets folder looks like this:

  assets/fonts/whatever.ttf
  assets/images/sprite.png
  assets/level.ron
  

  Then the output directory that you zip up and send off to itch should look something like

  index.html
  assets/images/sprite.png
  assets/level.ron
  images/sprite.png.meta
  level.ron.meta
  

• You can disable asset processing now

edit: unconfirmed, but I had some feedback on Discord that Itch still serves http 403 for the .meta files even if they are present. bevy_embedded_assets might be another workaround.

[P13L0v3r]

Since it wasn't said,

.set(AssetPlugin {
    mode: AssetMode::Unprocessed,
    ..default()
})

does not fix the issue.

[cart]

Yeah this needs fixing for 0.12.1, especially given that the next Bevy Jam is coming up / WASM builds are a big part of that.

I think long term the path forward is "asset packing/compression with manifests". That way we can record if a meta file exists in the manifest and avoid making the request. And WASM deployments should probably ultimately be using processing + packing anyway to cut down on bandwidth usage / loading times.

Short term, I think we should probably just add a knob that controls meta file lookup behavior. Ex:

enum AssetMetaMode {
    // Always look for meta files
    Always,
    // Only look up meta files for assets in the given list 
    AllowList(Vec<AssetPath<'static>),
    // Never look for meta files. The default loader meta values will be used
    Never,
}

Given that most people probably aren't using meta files at this point, this is probably the right "patch fix" approach. Users can just set this to AssetMetaMode::Never. Ideally we have a fix that requires no manual intervention, but I haven't thought of one yet.

[valyagolev]

Since nobody posted very specifically what to do here, answer is:

add .insert_resource(AssetMetaCheck::Never)

to your app before adding default plugins

[rparrett]

Since nobody posted very specifically what to do here, answer is:

There's some code in the linked PR that adds the workaround. Make sure you add this resource before DefaultPlugins.

[awwsmm]

Can confirm that this is still happening in 0.13.0 and that @valyagolev 's single-line change prevents 404s from spamming the browser console

[SK83RJOSH]

Just wanted to follow up and say that this should definitely be kept in/after 0.14.0 - my app almost entirely processes non-bevy game assets that will never have meta files. Including loading/mounting archives which gates all other types of file I/O from happening - which ironically means if that if this feature is enabled, the archives themselves can get gated/hung by the asset waiting for it's associated meta file to load.

Definitely something I can workaround by just letting those requests bypass the gate, but if someone else were to do something similar, and the archives themselves contain meta files... well it begins to get rather complicated quickly. 🙂

That said, if this is kept in 14.0.0, I think it would be worthwhile to investigate an approach that lets particular resources/loaders/processors opt-out of meta files, as plugins would likely not want to force users to disable meta files across the board/manually register all exceptions.

[mrchantey]

Single Page Applications

When serving assets from a typical SPA setup they will not load at all without AssetMetaCheck::Never. This is because example.com/assets/foo.meta redirects back to index.html which bevy will cheerfully attempt to read as a meta file.

btw heres the ^0.14 one-liner

app.world_mut().insert_resource(AssetMetaCheck::Never);

[benfrankel]

In bevy 0.14 the workaround is now:

app.add_plugins(DefaultPlugins.set(AssetPlugin {
    meta_check: AssetMetaCheck::Never,
}));

[SK83RJOSH]

Just wanted to follow up and say the move to making this a non-resource makes the story for plugins even more complicated than before. Now I have to offer guidance on disabling meta files before my plugin is loaded, rather than just opt-out if my plugin is loaded, which makes the user story more complex.

As mentioned before, it would be nice to make this something a given source opts into/out of, instead of having it be global setting.

[AgustinRamiroDiaz]

In bevy 0.14 the workaround is now:

app.add_plugins(DefaultPlugins.set(AssetPlugin {
    meta_check: AssetMetaCheck::Never,
}));

I think defaults are also needed

    app.add_plugins(DefaultPlugins.set(AssetPlugin {
        meta_check: AssetMetaCheck::Never,
        ..default()
    }));

[katopz]

This should be add to all example or AssetMetaCheck::Never by default. I lost a day and crying because of this! And everything should work by default by all mean. T-T