Use Framework SourceType for WASM pass-through assets in multi-client solutions by lewing · Pull Request #125329 · dotnet/runtime

lewing · 2026-03-09T13:15:39Z

Summary

When multiple Blazor WebAssembly client projects reference the same runtime pack, pass-through files (JS, maps, ICU data, native wasm) share a NuGet cache path. This causes duplicate Identity keys in the static web assets pipeline, crashing DiscoverPrecompressedAssets with an ArgumentException on ToDictionary.

Root Cause

PR #124125 correctly changed WASM ContentRoot from project-specific OutputPath copies to per-item %(RootDir)%(Directory) (pointing to the real file in the NuGet cache). This fixed staleness on incremental builds. However, when two WASM client projects reference the same runtime pack, shared files like dotnet.js.map now resolve to identical NuGet cache paths, producing duplicate Identity values.

Fix

Use the SWA Framework SourceType convention (dotnet/sdk#53135) to let the SDK handle materialization, rather than manual Copy tasks:

DefineStaticWebAssets registers pass-through files with SourceType="Framework" (using their NuGet cache paths)
UpdatePackageStaticWebAssets materializes them to per-project obj/fx/{SourceId}/ directories, transforming metadata:
- SourceType → Discovered
- SourceId → project PackageId
- BasePath → project StaticWebAssetBasePath
- AssetMode → CurrentProject
- Identity → materialized file path (unique per project)

Asset classification:

Pass-through files (JS, maps, ICU, native wasm, DLLs when WebCil disabled): Framework → materialized by SDK task
WebCil-converted files: SourceType="Computed" (already per-project in obj/webcil/)

This eliminates manual Copy/culture-handling logic from Browser.targets and properly models the relationship: framework assets adopted by each consuming project.

Dependencies

Requires SDK support for SourceType="Framework" from dotnet/sdk#53135.

Testing

Validated with patched SDK (Framework SourceType + MaterializeFrameworkAsset) + Browser.targets:

aspnetcore Components.TestServer (3 WASM clients): ✅ Build succeeded
- WasmMinimal: 22 framework + 205 webcil files
- WasmRemoteAuthentication: 20 framework + 204 webcil files
- BasicTestApp: 29 framework + 218 webcil files
Multi-client build (2 WASM clients): ✅ Framework assets materialized per project
Multi-client publish: ✅ Both clients produce fingerprinted files
Incremental rebuild: ✅ Timestamp-based skip
WebCil disabled (WasmEnableWebcil=false): ✅

Fixes crash introduced by Fix WASM boot config ContentRoot to use IntermediateOutputPath #124125
Depends on Add Framework SourceType for static web assets sdk#53135 (Framework SourceType support)
Supersedes Use Framework SourceType for WASM pass-through assets in multi-client solutions #125309 (copy-based approach)

Copilot

Pull request overview

This PR fixes a crash introduced by PR #124125 in multi-client Blazor WebAssembly solutions. When two WASM client projects reference the same runtime pack, pass-through assets (JS, maps, ICU data, native WASM) previously resolved to identical NuGet cache paths, causing duplicate Identity keys that crashed DiscoverPrecompressedAssets with an ArgumentException during ToDictionary. The fix materializes pass-through files to a per-project obj/fx/{PackageId}/ directory using the SourceType="Framework" convention from the SWA SDK (requires dotnet/sdk#53135).

Changes:

New _WasmFrameworkAssetPath property (obj/fx/{PackageId}/) for materializing pass-through assets
Pass-through files are partitioned from WebCil-converted files and copied to the per-project obj/fx/{PackageId}/ path, registered with SourceType="Framework" via a new DefineStaticWebAssets call
Satellite (culture) framework assets are handled with culture subdirectories, matching the existing ConvertDllsToWebcil behavior

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

… solutions Multi-WASM-client solutions crash with duplicate Identity keys in DiscoverPrecompressedAssets because pass-through files (JS, maps, ICU, native wasm) share the same NuGet cache path across projects. Instead of manually copying pass-throughs, use the SWA Framework SourceType convention: DefineStaticWebAssets registers them as SourceType="Framework", then UpdatePackageStaticWebAssets materializes them to per-project obj/fx/{SourceId}/ directories, transforming metadata (SourceType→Discovered, SourceId→PackageId, AssetMode→CurrentProject) and giving each project a unique Identity. This approach: - Eliminates manual Copy tasks from Browser.targets - Leverages the SDK's MaterializeFrameworkAsset for timestamp-based incremental copies - Properly models the relationship: framework assets adopted by each consuming project - Works with and without WebCil enabled Depends on dotnet/sdk#53135 for Framework SourceType support in the SDK. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

lewing · 2026-03-09T17:51:18Z

This will fail until the sdk with the Framework source type makes it to runtime

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

lewing · 2026-03-13T22:55:17Z

waiting on #125419 now

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lewing · 2026-03-14T17:17:14Z

@javiercn I know you have some follow-up planed to make this cleaner but it we need to get preview3 green asap, this is blocking dotnet/aspnetcore#65673

lewing · 2026-03-17T18:23:24Z

fix finally made it here

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

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

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

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Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

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

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

- Add PassThroughCandidates output to ConvertDllsToWebcil task so the task itself classifies which files are pass-throughs (non-DLL files from shared locations like the NuGet cache) vs converted webcil files. This replaces the fragile MSBuild string-comparison split that checked StartsWith(_WasmBuildWebcilPath) and incorrectly classified native build outputs in obj/wasm/for-build/ as Framework candidates. - Set AssetMode=All on materialized framework assets so they flow through project references to the host/server project in Blazor WASM hosted scenarios. UpdatePackageStaticWebAssets defaults to CurrentProject which prevents the server project from seeing client framework assets during publish. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

lewing · 2026-03-18T02:40:30Z

@akoeplinger how is the bootstrap sdk supposed to update now?

akoeplinger · 2026-03-18T10:27:47Z

@lewing the one in global.json you mean? normally the VMR/arcade sets the minimum version via rebootstrapping process in the VMR which then flows to repos via backflow.

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Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

Copilot · 2026-03-19T20:56:07Z

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

+    /// 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.


The XML doc for PassThroughCandidates says items with WasmNativeBuildOutput metadata are excluded, but Execute() assigns PassThroughCandidates = Candidates when IsEnabled is false, which will include those items. Please update the doc (or adjust the disabled-path behavior) so the exclusion rule matches what actually happens when WebCil is disabled.

Suggested change

/// 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.

/// When <see cref="IsEnabled"/> is true, items with WasmNativeBuildOutput metadata

/// (per-project native build outputs) are excluded — they're already unique per project.

/// When <see cref="IsEnabled"/> is false, all candidates (DLL and non-DLL), including

/// those with WasmNativeBuildOutput metadata, appear here with no additional filtering.

Copilot AI review requested due to automatic review settings March 9, 2026 13:15

lewing mentioned this pull request Mar 9, 2026

Use Framework SourceType for WASM pass-through assets in multi-client solutions #125309

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Add Framework SourceType for static web assets dotnet/sdk#53135

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lewing force-pushed the fix-wasm-framework-sourcetype branch from 9b1f0a8 to 1c6e5b6 Compare March 9, 2026 14:01

lewing requested a review from maraf March 9, 2026 14:05

lewing mentioned this pull request Mar 9, 2026

Handle duplicate static web asset identities gracefully dotnet/sdk#53305

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This was referenced Mar 9, 2026

BlazorWasm AOT not requiring trimming #125233

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BlazorWasm_CannotAOT_InDebug test failure #125244

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wtgodbe mentioned this pull request Mar 9, 2026

[main] Source code updates from dotnet/dotnet dotnet/aspnetcore#65673

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lewing requested a review from javiercn March 10, 2026 18:49

Merge branch 'main' into fix-wasm-framework-sourcetype

91040a0

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lewing assigned javiercn Mar 14, 2026

lewing assigned javiercn and unassigned lewing and javiercn Mar 14, 2026

build-analysis bot mentioned this pull request Mar 14, 2026

[browser] Wasm.Build.Tests timeout - Timed out after 10s waiting for 'WASM EXIT' #116697

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lewing enabled auto-merge (squash) March 17, 2026 18:40

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lewing force-pushed the fix-wasm-framework-sourcetype branch from 687f428 to fa33973 Compare March 18, 2026 01:07

Temporarily bump the sdk for testing

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-    /// 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.
+    /// When <see cref="IsEnabled"/> is true, items with WasmNativeBuildOutput metadata
+    /// (per-project native build outputs) are excluded — they're already unique per project.
+    /// When <see cref="IsEnabled"/> is false, all candidates (DLL and non-DLL), including
+    /// those with WasmNativeBuildOutput metadata, appear here with no additional filtering.

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lewing commented Mar 9, 2026 •

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