Deprecate the Blazor WebAssembly DevServer package by Copilot · Pull Request #67862 · dotnet/aspnetcore

Copilot · 2026-07-16T21:45:46Z

The standalone Blazor WebAssembly DevServer is being retired in favor of the newer Gateway host. This change makes that transition explicit by marking the package as deprecated, directing consumers to Gateway, and surfacing a clear startup warning so the migration path is visible where the package is actually used.

Package deprecation
- Mark Microsoft.AspNetCore.Components.WebAssembly.DevServer as deprecated in package metadata and document Microsoft.AspNetCore.Components.Gateway as the replacement.
- Update PACKAGE.md to present Gateway as the recommended hosting path for standalone Blazor WebAssembly apps.
Runtime guidance
- Emit a deprecation warning from blazor-devserver at startup so developers see the migration guidance immediately.
- Preserve the existing UseWebAssemblyDebugging() call with a targeted suppression comment so the DevServer project continues to build during the deprecation transition.

Co-authored-by: javiercn <6995051+javiercn@users.noreply.github.com>

Copilot

Pull request overview

This PR makes the retirement of the standalone Blazor WebAssembly DevServer explicit by updating its package messaging and adding a runtime startup warning that directs developers to the newer Gateway host.

Changes:

Updated DevServer package description and PACKAGE.md to state the package is deprecated and point to Microsoft.AspNetCore.Components.Gateway.
Added a startup-time log warning in the DevServer host to surface migration guidance when the package is actually used.
Normalized the XML prolog line in CompatibilitySuppressions.xml (removing a leading BOM/indentation).

Reviewed changes

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

File	Description
src/Framework/App.Runtime/src/CompatibilitySuppressions.xml	Normalizes the XML header line formatting (removes BOM/indentation).
src/Components/WebAssembly/DevServer/src/Server/Startup.cs	Logs a deprecation warning at startup; adds a logger dependency to `Configure`.
src/Components/WebAssembly/DevServer/src/PACKAGE.md	Updates package documentation to recommend Gateway over DevServer.
src/Components/WebAssembly/DevServer/src/Microsoft.AspNetCore.Components.WebAssembly.DevServer.csproj	Updates the NuGet description to clearly indicate deprecation and the replacement package.

+#pragma warning disable CS0618 // This middleware is deprecated as part of the DevServer deprecation path. The replacement is Microsoft.AspNetCore.Components.Gateway.
        app.UseWebAssemblyDebugging();
+#pragma warning restore CS0618


 ```

-Make sure that the newly-added `<PackageReference />` in the `.csproj` file includes `PrivateAssets="all"`:
+If you still need to reference the legacy package for compatibility reasons, make sure that the newly-added `<PackageReference />` in the `.csproj` file includes `PrivateAssets="all"`:


oroztocil

This PR and #67861 should decide what diagnostic to emit when obsoleting UseWebAssemblyDebugging and what warning to suppress src/Components/WebAssembly/DevServer/src/Server/Startup.cs.

oroztocil · 2026-07-17T13:27:55Z

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>


Nit: spurious BOM change

javiercn · 2026-07-17T13:50:45Z

@copilot fix the comments

Co-authored-by: javiercn <6995051+javiercn@users.noreply.github.com>

Copilot · 2026-07-17T14:02:28Z

@copilot fix the comments

Fixed in 1e555fc. Updated Startup.cs to suppress ASPDEPR011 (aligned with the UseWebAssemblyDebugging obsoletion), clarified the PACKAGE.md wording, and reverted the spurious BOM change in CompatibilitySuppressions.xml.

The obsoletion of UseWebAssemblyDebugging and its required suppression are owned by PR #67861. This PR only adds the DevServer deprecation startup warning; the ASPDEPR011 pragma is dropped here to avoid duplicating the suppression. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 9e4d745c-a233-409a-a399-2e2d750bc5c3

danroth27

LGTM

javiercn · 2026-07-17T18:50:03Z

@copilot resolve the merge conflicts in this pull request

Co-authored-by: javiercn <6995051+javiercn@users.noreply.github.com>

javiercn · 2026-07-18T11:07:23Z

@copilot

Restored D:\a_work\1\s\src\Servers\Connections.Abstractions\src\Microsoft.AspNetCore.Connections.Abstractions.csproj (in 4 ms).
Restored D:\a_work\1\s\src\Servers\HttpSys\perf\Microbenchmarks\Microsoft.AspNetCore.Server.HttpSys.Microbenchmarks.csproj (in 9 ms).
D:\a_work\1\s\src\Security\test\AuthSamples.FunctionalTests\AuthSamples.FunctionalTests.csproj : error NU1902: Warning As Error: Package 'AngleSharp' 0.9.9 has a known moderate severity vulnerability, GHSA-pgww-w46g-26qg [D:\a_work\1\s.dotnet\sdk\11.0.100-preview.6.26318.108\NuGet.targets]
Restored D:\a_work\1\s\src\Security\samples\StaticFilesAuth\StaticFilesAuth.csproj (in 37 ms).
Failed to restore D:\a_work\1\s\src\Security\test\AuthSamples.FunctionalTests\AuthSamples.FunctionalTests.csproj (in 60 ms).
Restored D:\a_work\1\s\src\Security\samples\PathSchemeSelection\PathSchemeSelection.csproj (in 72 ms).
Restored D:\a_work\1\s\src\Security\samples\Identity.ExternalClaims\Identity.ExternalClaims.csproj (in 73 ms).
Restored D:\a_work\1\s\src\Servers\IIS\IIS\test\IIS.NewHandler.FunctionalTests\IIS.NewHandler.FunctionalTests.csproj (in 4.09 sec).
Restored D:\a_work\1\s\src\Security\samples\CustomPolicyProvider\CustomPolicyProvider.csproj (in 49 ms).
Restored D:\a_work\1\s\src\Security\samples\CustomAuthorizationFailureResponse\CustomAuthorizationFailureResponse.csproj (in 48 ms).
Restored D:\a_work\1\s\src\Security\samples\DynamicSchemes\DynamicSchemes.csproj (in 62 ms).
Restored D:\a_work\1\s\src\Servers\IIS\IIS\test\testassets\InProcessNewShimWebSite\InProcessNewShimWebSite.csproj (in 4.53 sec).
Restored D:\a_work\1\s\src\Security\samples\Cookies\Cookies.csproj (in 48 ms).
Restored D:\a_work\1\s\src\Security\perf\Microbenchmarks\Microsoft.AspNetCore.Security.Microbenchmarks.csproj (in 11 ms).
Restored D:\a_work\1\s\src\Security\CookiePolicy\src\Microsoft.AspNetCore.CookiePolicy.csproj (in 5 ms).
Restored D:\a_work\1\s\src\Security\samples\ClaimsTransformation\ClaimsTransformation.csproj (in 40 ms).
Restored D:\a_work\1\s\src\Security\CookiePolicy\test\Microsoft.AspNetCore.CookiePolicy.Test.csproj (in 23 ms).
Restored D:\a_work\1\s\src\Security\CookiePolicy\samples\CookiePolicySample\CookiePolicySample.csproj (in 16 ms).
Restored D:\a_work\1\s\src\Security\Authorization\test\Microsoft.AspNetCore.Authorization.Test.csproj (in 26 ms).
1 of 586 projects are up-to-date for restore.

Build FAILED.

D:\a_work\1\s\src\Identity\test\Identity.Test\Microsoft.AspNetCore.Identity.Test.csproj : error NU1902: Warning As Error: Package 'AngleSharp' 0.9.9 has a known moderate severity vulnerability, GHSA-pgww-w46g-26qg [D:\a_work\1\s.dotnet\sdk\11.0.100-preview.6.26318.108\NuGet.targets]
D:\a_work\1\s\src\Identity\test\Identity.FunctionalTests\Microsoft.AspNetCore.Identity.FunctionalTests.csproj : error NU1902: Warning As Error: Package 'AngleSharp' 0.9.9 has a known moderate severity vulnerability, GHSA-pgww-w46g-26qg [D:\a_work\1\s.dotnet\sdk\11.0.100-preview.6.26318.108\NuGet.targets]
D:\a_work\1\s\src\Mvc\test\Mvc.FunctionalTests\Microsoft.AspNetCore.Mvc.FunctionalTests.csproj : error NU1902: Warning As Error: Package 'AngleSharp' 0.9.9 has a known moderate severity vulnerability, GHSA-pgww-w46g-26qg [D:\a_work\1\s.dotnet\sdk\11.0.100-preview.6.26318.108\NuGet.targets]
D:\a_work\1\s\src\Security\test\AuthSamples.FunctionalTests\AuthSamples.FunctionalTests.csproj : error NU1902: Warning As Error: Package 'AngleSharp' 0.9.9 has a known moderate severity vulnerability, GHSA-pgww-w46g-26qg [D:\a_work\1\s.dotnet\sdk\11.0.100-preview.6.26318.108\NuGet.targets]
0 Warning(s)
4 Error(s)

Time Elapsed 00:04:17.31
Build failed with exit code 1. Check errors above.
##[error]Cmd.exe exited with code '1'.
Finishing: Run restore.cmd

Rebase and fix the issue

…zor-devserver-package Co-authored-by: javiercn <6995051+javiercn@users.noreply.github.com>

Co-authored-by: javiercn <6995051+javiercn@users.noreply.github.com>

Copilot · 2026-07-18T11:18:49Z

@copilot

Restored D:\a_work\1\s\src\Servers\Connections.Abstractions\src\Microsoft.AspNetCore.Connections.Abstractions.csproj (in 4 ms).
...

Done in a0663f6. The branch was behind main (it was reverting the Identity #67731 changes), so I brought it up to date with the latest main. The only content difference from main is now the three intended DevServer files (csproj description, PACKAGE.md, Startup.cs startup warning), aligned with the ASPDEPR011 suppression from the already-merged #67861. The DevServer project builds with 0 warnings/0 errors.

On the restore failure: the NU1902 error for AngleSharp 0.9.9 is a pre-existing, repo-wide NuGet audit advisory unrelated to this PR — eng/Versions.props pins AngleSharp to 0.9.9 on the latest main too, and the failing projects (Identity.Test, Identity.FunctionalTests, Mvc.FunctionalTests, AuthSamples.FunctionalTests) are unrelated to the DevServer changes. Bumping/suppressing that advisory would be a separate, repo-wide change outside the scope of this deprecation PR; let me know if you'd like me to take it on separately.

Initial plan

9407d80

Copilot AI assigned Copilot and javiercn Jul 16, 2026

Copilot started work on behalf of javiercn July 16, 2026 21:46 View session

Copilot AI linked an issue Jul 16, 2026 that may be closed by this pull request

Deprecate the Microsoft.AspNetCore.Components.WebAssembly.DevServer package #67857

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Finalize DevServer deprecation changes

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Co-authored-by: javiercn <6995051+javiercn@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Deprecate Microsoft.AspNetCore.Components.WebAssembly.DevServer package~~ Deprecate the Blazor WebAssembly DevServer package Jul 16, 2026

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Deprecate UseWebAssemblyDebugging and remove it from Blazor templates #67861

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Address PR feedback on DevServer deprecation follow-ups

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Merge origin/main and resolve DevServer Startup conflict

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The Operation will be canceled. The next steps may not contain expected logs. dotnet/dnceng#3008

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Revert accidental googletest submodule bump

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Merge remote-tracking branch 'origin/main' into copilot/deprecate-bla…

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…zor-devserver-package Co-authored-by: javiercn <6995051+javiercn@users.noreply.github.com>

Add blank line before ASPDEPR011 suppression for readability

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		@@ -1,4 +1,4 @@
		<?xml version="1.0" encoding="utf-8"?>
		<?xml version="1.0" encoding="utf-8"?>

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