Use Framework SourceType for WASM pass-through assets in multi-client solutions

global.json

@@ -1,11 +1,11 @@
 {
   "sdk": {
-    "version": "11.0.100-preview.3.26161.119",
+    "version": "11.0.100-preview.3.26166.111",
     "allowPrerelease": true,
     "rollForward": "major"
   },
   "tools": {
-    "dotnet": "11.0.100-preview.3.26161.119"
+    "dotnet": "11.0.100-preview.3.26166.111"
   },
   "msbuild-sdks": {
     "Microsoft.DotNet.Arcade.Sdk": "11.0.0-beta.26166.111",

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets

@@ -307,7 +307,7 @@ Copyright (c) .NET Foundation. All rights reserved.
       <_WasmProjectAssemblyBuild Include="@(WasmAssembliesFinal)" Condition="$(_WasmIntermediateAssemblyFileNames.Contains(';%(FileName)%(Extension);'))" />
       <_WasmProjectAssemblyBuild Include="@(IntermediateAssembly)" Condition="@(_WasmProjectAssemblyBuild->Count()) == 0" />
       <_WasmBuildAssetCandidates Include="@(ReferenceCopyLocalPaths)" />
-      <_WasmBuildAssetCandidates Include="@(WasmNativeAsset)" />
+      <_WasmBuildAssetCandidates Include="@(WasmNativeAsset)" WasmNativeBuildOutput="true" />
       <_WasmBuildAssetCandidates Include="@(WasmAssembliesFinal)" />
       <_WasmBuildAssetCandidates Remove="@(_WasmProjectAssemblyBuild)" />
 
@@ -357,19 +357,29 @@ Copyright (c) .NET Foundation. All rights reserved.
 
     <ConvertDllsToWebcil Candidates="@(_BuildAssetsCandidates)" IntermediateOutputPath="$(_WasmBuildTmpWebcilPath)" OutputPath="$(_WasmBuildWebcilPath)" IsEnabled="$(_WasmEnableWebcil)">
       <Output TaskParameter="WebcilCandidates" ItemName="_WebcilAssetsCandidates" />
+      <Output TaskParameter="PassThroughCandidates" ItemName="_WasmFrameworkCandidates" />
       <Output TaskParameter="FileWrites" ItemName="FileWrites" />
     </ConvertDllsToWebcil>
 
+    <!-- Remove pass-throughs from webcil candidates so each file is classified exactly once:
+         webcil-converted files → Computed (per-project in obj/webcil/)
+         pass-through files → Framework (materialized per-project by UpdatePackageStaticWebAssets) -->
+    <ItemGroup>
+      <_WebcilAssetsCandidates Remove="@(_WasmFrameworkCandidates)" />
+    </ItemGroup>
+
     <ItemGroup>
       <!-- Set per-item ContentRoot so each asset's Identity matches its actual file on disk -->
       <_WebcilAssetsCandidates Update="@(_WebcilAssetsCandidates)" ContentRoot="%(RootDir)%(Directory)" />
+      <_WasmFrameworkCandidates Update="@(_WasmFrameworkCandidates)" ContentRoot="%(RootDir)%(Directory)" />
       <_WasmFingerprintPatterns Include="WasmFiles" Pattern="*.wasm" Expression="#[.{fingerprint}]!" />
       <_WasmFingerprintPatterns Include="DllFiles" Pattern="*.dll" Expression="#[.{fingerprint}]!" />
       <_WasmFingerprintPatterns Include="DatFiles" Pattern="*.dat" Expression="#[.{fingerprint}]!" />
       <_WasmFingerprintPatterns Include="Pdb" Pattern="*.pdb" Expression="#[.{fingerprint}]!" />
       <_WasmFingerprintPatterns Include="Symbols" Pattern="*.js.symbols" Expression="#[.{fingerprint}]!" />
     </ItemGroup>
 
+    <!-- Webcil-converted assets are per-project (Computed) — no materialization needed. -->
     <DefineStaticWebAssets
       CandidateAssets="@(_WebcilAssetsCandidates)"
       SourceId="$(PackageId)"
@@ -385,6 +395,46 @@ Copyright (c) .NET Foundation. All rights reserved.
       <Output TaskParameter="Assets" ItemName="WasmStaticWebAsset" />
     </DefineStaticWebAssets>
 
+    <!-- Pass-through files are Framework assets: they originate from the runtime pack but
+         need to be adopted by each consuming project. DefineStaticWebAssets registers them
+         with SourceType="Framework", then UpdatePackageStaticWebAssets materializes them to
+         a per-project obj/fx/{SourceId}/ directory, giving each project a unique Identity. -->
+    <DefineStaticWebAssets
+      CandidateAssets="@(_WasmFrameworkCandidates)"
+      SourceId="$(PackageId)"
+      SourceType="Framework"
+      AssetKind="Build"
+      AssetRole="Primary"
+      CopyToOutputDirectory="PreserveNewest"
+      CopyToPublishDirectory="Never"
+      FingerprintCandidates="$(_WasmFingerprintAssets)"
+      FingerprintPatterns="@(FingerprintPatterns);@(_WasmFingerprintPatterns)"
+      BasePath="$(StaticWebAssetBasePath)"
+    >
+      <Output TaskParameter="Assets" ItemName="_WasmFrameworkAssets" />
+    </DefineStaticWebAssets>
+
+    <!-- Let the SDK task handle materialization: copies to obj/fx/{SourceId}/, transforms
+         metadata (SourceType→Discovered, SourceId→PackageId, AssetMode→CurrentProject),
+         and remaps any existing endpoints to the new materialized paths. -->
+    <UpdatePackageStaticWebAssets
+      Assets="@(_WasmFrameworkAssets)"
+      IntermediateOutputPath="$(IntermediateOutputPath)"
+      ProjectPackageId="$(PackageId)"
+      ProjectBasePath="$(StaticWebAssetBasePath)"
+    >
+      <Output TaskParameter="UpdatedAssets" ItemName="_WasmMaterializedFrameworkAssets" />
+    </UpdatePackageStaticWebAssets>
+
+    <!-- Materialized framework assets must be visible to referencing projects (e.g. Blazor WASM
+         hosted scenarios where the server project serves the client's framework files).
+         UpdatePackageStaticWebAssets defaults AssetMode to CurrentProject, but WASM framework
+         files need to flow through project references for publish and serving. -->
+    <ItemGroup>
+      <_WasmMaterializedFrameworkAssets Update="@(_WasmMaterializedFrameworkAssets)" AssetMode="All" />
+      <WasmStaticWebAsset Include="@(_WasmMaterializedFrameworkAssets)" />
+    </ItemGroup>
+
     <DefineStaticWebAssets
       CandidateAssets="@(_WasmDiscoveredFileCandidates)"
       AssetTraitName="WasmResource"

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs

@@ -27,6 +27,16 @@ public class ConvertDllsToWebcil : Task
     [Output]
     public ITaskItem[] WebcilCandidates { get; set; }
 
+    /// <summary>
+    /// Non-DLL files from shared locations (runtime pack, NuGet cache) that were not
+    /// converted to webcil. These are candidates for Framework SourceType materialization.
+    /// When IsEnabled is false, all candidates (DLL and non-DLL) appear here.
+    /// Items with WasmNativeBuildOutput metadata (per-project native build outputs)
+    /// are excluded — they're already unique per project.
+    /// </summary>
+    [Output]
+    public ITaskItem[] PassThroughCandidates { get; set; }
+
     protected readonly List<string> _fileWrites = new();
 
     [Output]
@@ -35,10 +45,15 @@ public class ConvertDllsToWebcil : Task
     public override bool Execute()
     {
         var webcilCandidates = new List<ITaskItem>();
+        var passThroughCandidates = new List<ITaskItem>();
 
         if (!IsEnabled)
         {
+            // When webcil is disabled, no conversion occurs. All candidates pass
+            // through unchanged. All are also pass-through candidates since none
+            // were converted to webcil.
             WebcilCandidates = Candidates;
+            PassThroughCandidates = Candidates;
             return true;
         }
 
@@ -56,7 +71,19 @@ public override bool Execute()
 
             if (extension != ".dll")
             {
+                // Non-DLL files always appear in WebcilCandidates (backward compat
+                // for publish and other callers that only consume WebcilCandidates).
                 webcilCandidates.Add(candidate);
+
+                // Additionally classify shared framework files as pass-throughs.
+                // Items with WasmNativeBuildOutput metadata are per-project native
+                // build outputs (e.g. dotnet.native.wasm from obj/wasm/for-build/)
+                // that don't need Framework materialization.
+                bool isNativeBuildOutput = !string.IsNullOrEmpty(candidate.GetMetadata("WasmNativeBuildOutput"));
+                if (!isNativeBuildOutput)
+                {
+                    passThroughCandidates.Add(candidate);
+                }
                 continue;
             }
 
@@ -75,6 +102,7 @@ public override bool Execute()
         Directory.Delete(tmpDir, true);
 
         WebcilCandidates = webcilCandidates.ToArray();
+        PassThroughCandidates = passThroughCandidates.ToArray();
         return true;
     }