Blazor static assets - conflicting assets with the same path

[dazinator]

Scenario is to do with hosting two (multiple) different blazor wasm client applications, from a single .net core host project, and serving the correct one up on the root "/" url.

Prior to Blazor 3.2 preview 2, a single host could chose to serve up different front end client wasm projects on the root path, based on some logic like this:

if(isTenantA)
{
     app.UseClientSideBlazorFiles<ClientA.Program>() 
    /// stuff 
    endpoints.MapFallbackToClientSideBlazor<ClientA.Program>("index.html") 
    
}
else
{
     app.UseClientSideBlazorFiles<ClientB.Program>() 
    /// stuff 
    endpoints.MapFallbackToClientSideBlazor<ClientB.Program>("index.html") 
}

In this scenario, there are two blazor client wasm projects, and the host can serve up the correct one based on a decision it makes such as who is the current tenant. This sets up a FileProvider pointing to the correct wasm's static content location. The client wasm projects can all have files named "image1.png" but there are no conflicts - no issues.

After the upgrade to blazor 3.2 preview 2 and the switch to using static assets - it looks like it will have to become something like this:

appBuilder.UseBlazorFrameworkFiles(); // blazor framework files can be served up from root url path

if(isTenantA)
{
 // we want to serve up "ClientA" spa on the root path "/"
 IFileProvider fp = GetStaticFileProviderFor<ClientA.Program>();              
endpoints.MapFallbackToFile("index.html", new StaticFileOptions()
{
     FileProvider = fp
});           
}
else
{
// we want to serve up "ClientB" spa on the root path "/"
IFileProvider fp = GetStaticFileProviderFor<ClientB.Program>();              
endpoints.MapFallbackToFile("index.html", new StaticFileOptions()
{
     FileProvider = fp
});           
}

Where GetStaticFileProviderFor<TProgramType>(); is a method I'll have to write myself that builds a FileProvider that only resolves the particular SPA's static content, but on the root "/" request path.

However the first issue is that the client SPA projects that are referenced from the host (via a project reference) now cause a build error as they each have a file with the same name in their wwwroot directories - so I now get this build error that I didn't see previoulsy:

Severity	Code	Description	Project	File	Line	Suppression State
Error		Conflicting assets with the same path '/images/FOO_Black_Green_Logo_RGB.svg' for content root paths 'C:\Users\DarrellTunnell\source\repos\FOO\src\FOO.Landing.Page\wwwroot\images\FOO_Black_Green_Logo_RGB.svg' and 'C:\Users\DarrellTunnell\source\repos\FOO\src\FOO.Client\wwwroot\Images\FOO_Black_Green_Logo_RGB.svg'.	FOO.Server	C:\Program Files\dotnet\sdk\3.1.102\Sdks\Microsoft.NET.Sdk.Razor\build\netstandard2.0\Microsoft.NET.Sdk.Razor.StaticWebAssets.targets	191	

After doing some more research, I found that I can potentially resolve this error by setting <StaticWebAssetBasePath> in each client SPA project to be something unique.

However suppose I do set that for each wasm:

<StaticWebAssetBasePath>clientA</StaticWebAssetBasePath>

<StaticWebAssetBasePath>clientB</StaticWebAssetBasePath>

I still have to implement the aforementioned GetStaticFileProviderFor<TProgramType>(); method to set up an IFileProvider that will serve from the correct static assets location (ClientA vs ClientB) but serve that content up on the root path "/". I also need to make sure that I am serving the tenant up the SPA ClientA - then they should not be able to request files for /ClientB SPA. I know that Environment.WebRootFileProvider will be configured by default to be able to resolve both SPA's static assets on their Static Assets base paths: "/ClientA" and "/ClientB" respectively and I need to prevent that from happening.

I am pretty sure the key to this lies in building an IFileProvider to serve static assets based on the "StaticWebAssetBasePath" that I provide, but serve those files up on a different path i.e "/". In addition to this concern is working out how to replace or prevent the Environment.WebRootFileProvider from serving up Static Assets on their "StaticWebAssetBasePath"'s by default, so I can instead use the above IFileProvider via some additiopnal static files middleware to be explicit about the SPA i can serve up.

Any guidance on the resolution of this issue that did not exist in preview 1 would be greatly appreciated. Thanks

[dazinator]

I'm now thinking of this idea #20605

Set each clients StaticWebAssetBasePath to a path that should be hidden by the FileProvider by prefixing the path with a "."

<StaticWebAssetBasePath>.clientA</StaticWebAssetBasePath>

<StaticWebAssetBasePath>.clientB</StaticWebAssetBasePath>

This should result in the SPA static files being hidden by default, then I can add my own IFileProvider to the WebRootFileProvider that will serve up the correct SPA static files based on the tenant (I'll create a PhysicalFileProvider pointing to the "wwwroot/.clientA" and another for "wwwroot/.clientB" and wrap them in a custom IFileProvider that defers to the correct one of those depending on the current tenant.

This will work after a dotnet publish, but in development mode, i'll need #20605 to be fixed for the proper behaviour to work at development time too - i.e those static paths should not be served up by default.

[dazinator]

I'll close this - setting <StaticWebAssetBasePath> in each project to a unique path resolves the immediate build issue with conflictint static asset paths. However that leads to #20605