[browser] Use Runtime=NET for build tasks in WebAssembly SDK #123304

Copilot · 2026-01-17T10:35:27Z

Tested manually with Visual Studio (2026) Canary

Description

Aligns WebAssembly SDK pack tasks with MSBuild's Runtime="NET" attribute, dropping legacy multi-targeting for a simpler NuGet package layout.

Changes

Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.csproj

Single-target to $(NetCoreAppToolCurrent) (was multi-targeting net472)
Package tasks DLL/PDB directly in tools/ (was tools/{tfm}/)
GetFilesToPackage target uses $(OutputPath) which automatically includes TFM for single-targeted projects

Microsoft.NET.Sdk.WebAssembly.Browser.targets

Remove _WebAssemblySdkTasksTFM property and MSBuildRuntimeType-based TFM selection
Update assembly path: tools/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.dll (was tools/{tfm}/...)
Add Runtime="NET" to UsingTask declarations (without TaskFactory as it's redundant) for:
- GenerateWasmBootJson
- ComputeWasmBuildAssets
- ComputeWasmPublishAssets
- ConvertDllsToWebCil

WasmApp.InTree.props

Update _WebAssemblySdkToolsDirectory to include $(NetCoreAppToolCurrent) in path for in-tree builds

eng/testing/linker/trimmingTests.targets

Update WasmSdkPackTasksPath to include $(NetCoreAppToolCurrent) in path for in-tree builds

NuGet Package Layout

Before:

tools/
  net11.0/
    Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.dll
  net472/
    Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.dll

After:

tools/
  Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.dll

The Runtime="NET" attribute ensures tasks run on .NET Core regardless of MSBuild host. The TaskFactory attribute is omitted as MSBuild automatically uses the appropriate factory when Runtime="NET" is specified. In-tree build configurations are updated to correctly locate the tasks assembly in the single-target output structure (artifacts/bin/.../Release/net11.0/).

Original prompt

This PR refactors the WebAssembly SDK pack tasks and packaging setup to align with recent MSBuild improvements for selecting .NET runtime for tasks. The change leverages the Runtime="NET" attribute in UsingTask and drops the legacy multi-targeting of the tasks assembly, with a simpler NuGet layout:

The Microsoft.NET.Sdk.WebAssembly.Pack.Tasks project is now single-targeted to $(NetCoreAppToolCurrent).

The tasks DLL (and PDB) are placed directly in the NuGet package's tools/ directory, no TFM-specific subfolders.

_WebAssemblySdkTasksTFM and related target framework selection logic is removed from targets and msbuild snippets.

All declarations for tasks from Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.dll now set Runtime="NET", ensuring the correct runtime is used for execution irrespective of the outer build TFM.

This modernization streamlines task loading, package output, and better supports future .NET SDKs. Builds with older MSBuild (without UsingTask-runtime support) are not supported by this change.

This pull request was created from Copilot chat.

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

…arget layout - Change Microsoft.NET.Sdk.WebAssembly.Pack.Tasks to single-target $(NetCoreAppToolCurrent) - Update GetFilesToPackage to place DLLs/PDBs directly in tools/ (no TFM subfolders) - Remove _WebAssemblySdkTasksTFM property logic from Browser.targets - Add Runtime="NET" attribute to all UsingTask declarations for the tasks Co-authored-by: maraf <10020471+maraf@users.noreply.github.com>

maraf · 2026-01-17T11:25:25Z

@copilot There is a build error

D:\a\_work\1\s\src\mono\nuget\Microsoft.NET.Sdk.WebAssembly.Pack\build\Microsoft.NET.Sdk.WebAssembly.Browser.targets(309,5): error MSB4062: The "Microsoft.NET.Sdk.WebAssembly.ComputeWasmBuildAssets" task could not be loaded from the assembly D:\a\_work\1\s\artifacts\bin\\Microsoft.NET.Sdk.WebAssembly.Pack.Tasks\Release\Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.dll. Could not load file or assembly 'D:\a\_work\1\s\artifacts\bin\\Microsoft.NET.Sdk.WebAssembly.Pack.Tasks\Release\Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.dll'. The system cannot find the file specified. Confirm that the <UsingTask> declaration is correct, that the assembly and all its dependencies are available, and that the task contains a public class that implements Microsoft.Build.Framework.ITask. [D:\a\_work\1\s\src\libraries\Common\tests\Common.Tests.csproj::TargetFramework=net11.0-browser]

Fix it by adding <AppendRuntimeIdentifierToOutputPath>false</AppendRuntimeIdentifierToOutputPath> to Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.csproj.

Single-targeted projects still output to $(OutputPath)$(TargetFramework)\ directory. Update GetFilesToPackage to correctly locate DLLs/PDBs in the TFM subfolder. Co-authored-by: maraf <10020471+maraf@users.noreply.github.com>

Copilot · 2026-01-17T11:29:50Z

@copilot There is a build error

D:\a\_work\1\s\src\mono\nuget\Microsoft.NET.Sdk.WebAssembly.Pack\build\Microsoft.NET.Sdk.WebAssembly.Browser.targets(309,5): error MSB4062: The "Microsoft.NET.Sdk...

Fixed in f8ac36d. The GetFilesToPackage target now uses $(OutputPath)$(TargetFramework)\*.dll to correctly locate files in the single TFM subfolder (e.g., bin/Release/net11.0/).

maraf · 2026-01-17T13:14:15Z

@copilot Your last change did not fix the issue.

There is a build error

D:\a\_work\1\s\src\mono\nuget\Microsoft.NET.Sdk.WebAssembly.Pack\build\Microsoft.NET.Sdk.WebAssembly.Browser.targets(309,5): error MSB4062: The "Microsoft.NET.Sdk.WebAssembly.ComputeWasmBuildAssets" task could not be loaded from the assembly D:\a\_work\1\s\artifacts\bin\\Microsoft.NET.Sdk.WebAssembly.Pack.Tasks\Release\Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.dll. Could not load file or assembly 'D:\a\_work\1\s\artifacts\bin\\Microsoft.NET.Sdk.WebAssembly.Pack.Tasks\Release\Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.dll'. The system cannot find the file specified. Confirm that the <UsingTask> declaration is correct, that the assembly and all its dependencies are available, and that the task contains a public class that implements Microsoft.Build.Framework.ITask. [D:\a\_work\1\s\src\libraries\Common\tests\Common.Tests.csproj::TargetFramework=net11.0-browser]

Fix it by adding <AppendRuntimeIdentifierToOutputPath>false</AppendRuntimeIdentifierToOutputPath> to Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.csproj.

Update WasmApp.InTree.props and trimmingTests.targets to include $(NetCoreAppToolCurrent) in the tasks assembly path for in-tree builds, matching the single-target output structure. Co-authored-by: maraf <10020471+maraf@users.noreply.github.com>

Copilot · 2026-01-17T13:19:53Z

@copilot Your last change did not fix the issue.

There is a build error
...

Fixed in 813dae0. The issue was that in-tree build configurations in WasmApp.InTree.props and trimmingTests.targets were pointing to the old path structure without the TFM subfolder. Updated both files to include $(NetCoreAppToolCurrent) in the path: $(ArtifactsBinDir)Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/$(RuntimeConfiguration)/$(NetCoreAppToolCurrent)/

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

maraf · 2026-01-18T21:40:18Z

@copilot Remove all TaskFactory from UsingTask that you changed in the this PR

TaskFactory is not needed when Runtime="NET" is specified, as MSBuild automatically uses the appropriate factory. Co-authored-by: maraf <10020471+maraf@users.noreply.github.com>

Copilot · 2026-01-18T21:45:52Z

@copilot Remove all TaskFactory from UsingTask that you changed in the this PR

Done in 0ef24ca. Removed TaskFactory="TaskHostFactory" from all four UsingTask declarations as it's redundant when Runtime="NET" is specified.

dotnet-policy-service · 2026-01-18T22:01:36Z

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR modernizes the WebAssembly SDK pack tasks to use MSBuild's Runtime="NET" attribute, dropping legacy multi-targeting support and simplifying the NuGet package layout. The change aligns with recent MSBuild improvements for selecting .NET runtime for tasks.

Changes:

Single-target the Microsoft.NET.Sdk.WebAssembly.Pack.Tasks project to $(NetCoreAppToolCurrent), removing net472 multi-targeting
Simplify NuGet package layout by placing tasks DLL/PDB directly in tools/ instead of tools/{tfm}/ subdirectories
Add Runtime="NET" to all UsingTask declarations and remove the now-unnecessary TaskFactory attribute
Update in-tree build paths to include $(NetCoreAppToolCurrent) to match the single-target output structure

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.csproj	Single-targets to $(NetCoreAppToolCurrent) and simplifies GetFilesToPackage target to output directly to tools/
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Removes _WebAssemblySdkTasksTFM logic, updates assembly path, and adds Runtime="NET" to UsingTask declarations
src/mono/browser/build/WasmApp.InTree.props	Updates _WebAssemblySdkToolsDirectory path to include $(NetCoreAppToolCurrent) for in-tree builds
eng/testing/linker/trimmingTests.targets	Updates WasmSdkPackTasksPath to include $(NetCoreAppToolCurrent) for in-tree builds

Initial plan

50ef4fe

Copilot AI assigned Copilot and maraf Jan 17, 2026

Copilot started work on behalf of maraf January 17, 2026 10:35 View session

Copilot AI changed the title ~~[WIP] Refactor WebAssembly SDK pack tasks and packaging setup~~ Refactor WebAssembly SDK pack tasks to use Runtime="NET" and single-target layout Jan 17, 2026

Copilot AI requested a review from maraf January 17, 2026 10:46

Copilot finished work on behalf of maraf January 17, 2026 10:46

Copilot started work on behalf of maraf January 17, 2026 11:25 View session

Fix GetFilesToPackage to use TargetFramework subfolder

f8ac36d

Single-targeted projects still output to $(OutputPath)$(TargetFramework)\ directory. Update GetFilesToPackage to correctly locate DLLs/PDBs in the TFM subfolder. Co-authored-by: maraf <10020471+maraf@users.noreply.github.com>

Copilot finished work on behalf of maraf January 17, 2026 11:32

Copilot started work on behalf of maraf January 17, 2026 13:14 View session

Copilot finished work on behalf of maraf January 17, 2026 13:21

teo-tsirpanis reviewed Jan 17, 2026

View reviewed changes

...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets Outdated Show resolved Hide resolved

OutputPath already contains TFM if not multi-targeting

70fab51

Copilot started work on behalf of maraf January 18, 2026 17:31 View session

Copilot finished work on behalf of maraf January 18, 2026 17:35

This was referenced Jan 18, 2026

[wasm/browser] Failed to connect to socket /run/dbus/system_bus_socket #120176

Open

[wasm] Microsoft.Playwright.TargetClosedException : Target page, context or browser has been closed #121195

Open

Merge branch 'main' into copilot/refactor-webassembly-sdk-pack-tasks

0f5522c

Copilot started work on behalf of maraf January 18, 2026 21:40 View session

Remove TaskFactory from UsingTask declarations with Runtime="NET"

0ef24ca

TaskFactory is not needed when Runtime="NET" is specified, as MSBuild automatically uses the appropriate factory. Co-authored-by: maraf <10020471+maraf@users.noreply.github.com>

Copilot finished work on behalf of maraf January 18, 2026 21:47

maraf added arch-wasm WebAssembly architecture area-Build-mono os-browser Browser variant of arch-wasm labels Jan 18, 2026

maraf added this to the 11.0.0 milestone Jan 18, 2026

build-analysis bot mentioned this pull request Jan 19, 2026

"We stopped hearing from agent Azure Pipelines 32. Verify the agent machine is running and has a healthy network connection" dotnet/dnceng#1886

Open

3 tasks

Merge branch 'main' into copilot/refactor-webassembly-sdk-pack-tasks

2bcfe1b

maraf changed the title ~~Refactor WebAssembly SDK pack tasks to use Runtime="NET" and single-target layout~~ [browser] Use Runtime=NET for build tasks in WebAssembly SDK Jan 20, 2026

maraf marked this pull request as ready for review January 20, 2026 16:24

maraf requested a review from lewing as a code owner January 20, 2026 16:24

Copilot AI review requested due to automatic review settings January 20, 2026 16:24

maraf requested a review from akoeplinger as a code owner January 20, 2026 16:24

maraf requested a review from a team January 20, 2026 16:25

Copilot started reviewing on behalf of maraf January 20, 2026 16:25 View session

Copilot AI reviewed Jan 20, 2026

View reviewed changes

javiercn approved these changes Jan 20, 2026

View reviewed changes

Merge branch 'main' into copilot/refactor-webassembly-sdk-pack-tasks

7902812

This was referenced Jan 21, 2026

JSImportTest.BadCast test failure #111449

Open

[browser][coreCLR] Unable to load shared library libSystem.Runtime.InteropServices.JavaScript.Native #123421

Open

maraf merged commit 46c884e into main Jan 21, 2026
160 of 163 checks passed

maraf deleted the copilot/refactor-webassembly-sdk-pack-tasks branch January 21, 2026 16:52

This was referenced Jan 21, 2026

[prvysoky/demo] Source code updates from dotnet/runtime dotnet/dotnet#4337

Closed

[prvysoky/demo] Source code updates from dotnet/runtime dotnet/dotnet#4340

Closed

[main] Source code updates from dotnet/runtime dotnet/dotnet#4351

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

[browser] Use Runtime=NET for build tasks in WebAssembly SDK #123304

[browser] Use Runtime=NET for build tasks in WebAssembly SDK #123304

Uh oh!

Copilot AI commented Jan 17, 2026 •

edited by maraf

Loading

Uh oh!

maraf commented Jan 17, 2026

Uh oh!

Copilot AI commented Jan 17, 2026

Uh oh!

maraf commented Jan 17, 2026

Uh oh!

Copilot AI commented Jan 17, 2026

Uh oh!

Uh oh!

maraf commented Jan 18, 2026

Uh oh!

Copilot AI commented Jan 18, 2026

Uh oh!

dotnet-policy-service bot commented Jan 18, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

[browser] Use Runtime=NET for build tasks in WebAssembly SDK #123304

[browser] Use Runtime=NET for build tasks in WebAssembly SDK #123304

Uh oh!

Conversation

Copilot AI commented Jan 17, 2026 • edited by maraf Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Description

Changes

NuGet Package Layout

Uh oh!

maraf commented Jan 17, 2026

Uh oh!

Copilot AI commented Jan 17, 2026

Uh oh!

maraf commented Jan 17, 2026

Uh oh!

Copilot AI commented Jan 17, 2026

Uh oh!

Uh oh!

maraf commented Jan 18, 2026

Uh oh!

Copilot AI commented Jan 18, 2026

Uh oh!

dotnet-policy-service bot commented Jan 18, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Copilot AI commented Jan 17, 2026 •

edited by maraf

Loading