Support WebGL.Texture like File.File

[lydell]

When using WebGL, you might use WebGL.load to load a texture and store it in the model so you can use it later to render WebGL stuff. However, that type contains a function, which has a few problems:

• It can’t be transferred correctly from and old app to a new app when migrating during a release. Your new app will crash when it tries to use the texture.
• There is no compilation error if you put it in ToFrontend and ToBackend msgs, but it can’t be serialized due to the function inside.

The File type from elm/file used to have the same problems, but Lamdera has added support for it. We should do the same for Texture.

• Support Texture in the wire format using references:

  • compiler/extra/Lamdera/Wire3/Decoder.hs

    Lines 351 to 352 in 74a141e

    	-- Frontend only JS reference types
    	TType (Module.Canonical (Name "elm" "file") "File") "File" params -> callDecoder "decodeRef" tipe

  • compiler/extra/Lamdera/Wire3/Encoder.hs

    Lines 214 to 216 in 74a141e

    	-- Frontend only JS reference types
    	TType (Module.Canonical (Name "elm" "file") "File") "File" _ ->
    	(a (VarForeign mLamdera_Wire "encodeRef" (Forall Map.empty (TLambda tipe tLamdera_Wire_Encoder))))

  • compiler/extra/Lamdera/Wire3/Helpers.hs

    Lines 123 to 125 in 74a141e

    	-- JS types we are supporting through JS ref encodings. These serialisations
    	-- CANNOT BE DECODED OUTSIDE OF THE JS SCOPE THEY WERE ENCODED IN!
    	TType (Module.Canonical (Name "elm" "file") "File") "File" _ -> False

• Disallow Texture unless inside FrontendMsg or FrontendModel:

  compiler/extra/Lamdera/TypeHash.hs

  Lines 390 to 395 in 74a141e

  	-- Frontend JS Kernel types
  	("elm", "file", "File", "File") ->
  	if targetName `elem` ["FrontendMsg", "FrontendModel"] then
  	DKernelBrowser "File.File"
  	else
  	kernelErrorBrowserOnly

There might be a test case or something that needs updating too.

[lydell]

Note: We should probably do the same to Browser.Navigation.Key. Then we can get rid of some hacks in Injection.hs. Remember, Browser.Navigation.Key is stored in the model and the model is transferred to the new app during migration. It also doesn’t make sense to send it to the backend.

[supermario]

@lydell merged the fix for WebGL.Texture – lets tackle the Browser.Navigation.Key thing separately as I think there's more moving parts to consider holistically there.