Fix blazor-gateway.dll not found: pack BlazorGateway subfolder into wasm packages by Copilot · Pull Request #130764 · dotnet/runtime

Copilot · 2026-07-15T10:03:50Z

The WasmAppHost browser dev server launches the Blazor Gateway from a BlazorGateway/ subfolder next to WasmAppHost.dll, but the wasm packaging projects collected WasmAppHost output with a non-recursive glob ($(WasmAppHostDir)\*). The subfolder — and blazor-gateway.dll — was omitted from the shipped packages, so GatewayServer.LocateGatewayDll() threw FileNotFoundException at runtime (observed in Wasm.Build.Tests).

Changes

Pack the BlazorGateway subtree recursively in the three pkgprojs that ship WasmAppHost (Microsoft.NET.Sdk.WebAssembly.Pack, Microsoft.NET.Runtime.WebAssembly.Sdk, Microsoft.NET.Runtime.WebAssembly.Wasi.Sdk), preserving the folder structure so the payload lands at WasmAppHost/BlazorGateway/.
Two-step %(RecursiveDir) transform — the subtree is globbed into a raw item first, then re-included with TargetPath, because %(RecursiveDir) is not populated when referenced on the same wildcard Include (would otherwise flatten nested files).

<_WasmAppHostFiles Include="$(WasmAppHostDir)\*" TargetPath="WasmAppHost" />
<_WasmAppHostGatewayFiles Include="$(WasmAppHostDir)\BlazorGateway\**\*" />
<_WasmAppHostFiles Include="@(_WasmAppHostGatewayFiles)" TargetPath="WasmAppHost\BlazorGateway\%(RecursiveDir)" />

The Arcade packer treats the extension-less TargetPath as a directory and appends the filename, producing WasmAppHost/BlazorGateway/blazor-gateway.dll — the exact path the loader searches.

Co-authored-by: pavelsavara <[email protected]>

azure-pipelines · 2026-07-15T10:04:34Z

Azure Pipelines: Successfully started running 4 pipeline(s). 11 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

maraf · 2026-07-15T10:31:15Z

Does the subprocess approach work with HotReload?

Co-authored-by: pavelsavara <[email protected]>

Copilot

Pull request overview

This PR updates the browser WASM toolchain to ship and launch the Blazor Gateway (blazor-gateway.dll) correctly by (1) copying the Gateway payload next to WasmAppHost under a BlazorGateway/ subfolder and (2) ensuring the WASM SDK NuGet packages pack that subfolder recursively so runtime lookup succeeds.

Changes:

Copy Microsoft.AspNetCore.Components.Gateway payload into the WasmAppHost output under BlazorGateway/.
Replace the in-proc dev server implementation with a subprocess-based GatewayServer that locates and launches blazor-gateway.dll.
Pack the WasmAppHost/BlazorGateway/ subtree recursively into the three WASM SDK packages; also enable SPA fallback default for root apps.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/mono/wasm/host/WasmAppHost.csproj	Adds Gateway package reference + copies/packs its `tools/**` payload next to WasmAppHost.
src/mono/wasm/host/README.md	Documents Gateway-based dev server behavior and known feature gaps vs legacy server.
src/mono/wasm/host/DevServer/WebAssemblyNetDebugProxyAppBuilderExtensions.cs	Removes legacy debugging middleware implementation.
src/mono/wasm/host/DevServer/GatewayServer.cs	Adds subprocess launcher that parses Gateway stdout to determine listening URLs.
src/mono/wasm/host/DevServer/DevServerStartup.cs	Removes legacy in-process dev server startup pipeline.
src/mono/wasm/host/DevServer/DevServer.cs	Removes legacy dev server host builder entrypoint.
src/mono/wasm/host/DevServer/DebugProxyLauncher.cs	Removes legacy debug proxy launcher implementation.
src/mono/wasm/host/DevServer/ContentEncodingNegotiator.cs	Removes legacy content-encoding negotiation middleware.
src/mono/wasm/host/BrowserHost.cs	Routes static web assets scenario to the new `GatewayServer` and warns about missing console forwarding.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/Microsoft.NET.Sdk.WebAssembly.Pack.pkgproj	Packs `WasmAppHost/BlazorGateway/**` recursively into the package.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.props	Sets `StaticWebAssetSpaFallbackEnabled=true` by default for root apps.
src/mono/nuget/Microsoft.NET.Runtime.WebAssembly.Wasi.Sdk/Microsoft.NET.Runtime.WebAssembly.Wasi.Sdk.pkgproj	Packs `WasmAppHost/BlazorGateway/**` recursively into the package.
src/mono/nuget/Microsoft.NET.Runtime.WebAssembly.Sdk/Microsoft.NET.Runtime.WebAssembly.Sdk.pkgproj	Packs `WasmAppHost/BlazorGateway/**` recursively into the package.
eng/Versions.props	Adds a pinned Gateway package version property consumed by WasmAppHost.

+    <_blazorGatewayFiles Include="$(PkgMicrosoft_AspNetCore_Components_Gateway)\tools\**\*" />
+    <None Include="@(_blazorGatewayFiles)" CopyToOutputDirectory="PreserveNewest" Link="BlazorGateway\%(RecursiveDir)%(Filename)%(Extension)" />
+    <PackageFile Include="@(_blazorGatewayFiles)" TargetPath="tools\$(NetCoreAppCurrent)\BlazorGateway\%(RecursiveDir)" />


+        await host.StartAsync(token);
+
+        ServerURLs serverUrls = await realUrlsAvailableTcs.Task;
+        return (serverUrls, host);


+        Match listeningMatch = NowListeningRegex.Match(line);
+        if (listeningMatch.Success)
+        {
+            lock (_listeningUrls)
+            {
+                _listeningUrls.Add(listeningMatch.Groups["url"].Value.Trim());
+            }
+        }
+        else if (ApplicationStartedRegex.IsMatch(line))
+        {
+            ResolveServerUrls();
+        }
+
+        // Suppress the gateway's own status messages so they are not confused with the application's output.
+        foreach (string prefix in MessageSuppressionPrefixes)
+        {
+            if (line.StartsWith(prefix, StringComparison.Ordinal))
+                return;
+        }
+
+        Console.WriteLine(line);
+    }
+
+    private void OnErrorDataReceived(object sender, DataReceivedEventArgs eventArgs)
+    {
+        if (!string.IsNullOrEmpty(eventArgs.Data))
+            _logger.LogError("[BlazorGateway] {Message}", eventArgs.Data);
+    }
+
+    private void ResolveServerUrls()
+    {
+        string? http;
+        string? https;
+        lock (_listeningUrls)
+        {
+            http = GetServerAddress(_listeningUrls, secure: false);
+            https = GetServerAddress(_listeningUrls, secure: true);
+        }
+
+        if (http is null)
+            _realUrlsAvailableTcs.TrySetException(new InvalidOperationException("Failed to determine the Blazor Gateway's HTTP address or port."));
+        else
+            _realUrlsAvailableTcs.TrySetResult(new ServerURLs(http, https));
+    }


Copilot AI and others added 3 commits July 15, 2026 09:52

Unify WasmAppHost dev server with Blazor Gateway (subprocess)

ea14e83

Co-authored-by: pavelsavara <[email protected]>

Address code review: simplify GatewayServer lifetime and process launch

1dbe763

Co-authored-by: pavelsavara <[email protected]>

Tidy GatewayServer: warn on stop failure, tighten regex timeout

5e70b59

Co-authored-by: pavelsavara <[email protected]>

Copilot AI self-assigned this Jul 15, 2026

Copilot AI review requested due to automatic review settings July 15, 2026 10:03

Copilot AI assigned pavelsavara Jul 15, 2026

Copilot AI removed the request for review from Copilot July 15, 2026 10:03

Copilot created this pull request from a session on behalf of pavelsavara July 15, 2026 10:03 View session

Copilot started work on behalf of pavelsavara July 15, 2026 10:09 View session

github-actions Bot added the area-Build-mono label Jul 15, 2026

Copilot AI requested a review from pavelsavara July 15, 2026 10:19

Copilot finished work on behalf of pavelsavara July 15, 2026 10:19

pavelsavara added arch-wasm WebAssembly architecture os-browser Browser variant of arch-wasm labels Jul 15, 2026

pavelsavara mentioned this pull request Jul 15, 2026

Blazor Gateway dev-server gaps for runtime/WBT dotnet/aspnetcore#67814

Open

Copilot started work on behalf of pavelsavara July 15, 2026 11:52 View session

Pack BlazorGateway subfolder into wasm SDK/pack packages

8127015

Co-authored-by: pavelsavara <[email protected]>

Copilot AI requested review from Copilot and removed request for Copilot July 15, 2026 12:05

Copilot AI changed the title ~~Unify WasmAppHost dev server with Blazor Gateway~~ Fix blazor-gateway.dll not found: pack BlazorGateway subfolder into wasm packages Jul 15, 2026

Copilot finished work on behalf of pavelsavara July 15, 2026 12:07

set StaticWebAssetSpaFallbackEnabled

140bef6

Copilot AI review requested due to automatic review settings July 15, 2026 14:17

pavelsavara temporarily deployed to copilot-pat-pool July 15, 2026 14:17 — with GitHub Actions Inactive

Copilot started reviewing on behalf of pavelsavara July 15, 2026 14:18 View session

Copilot AI reviewed Jul 15, 2026

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Fix blazor-gateway.dll not found: pack BlazorGateway subfolder into wasm packages#130764

Fix blazor-gateway.dll not found: pack BlazorGateway subfolder into wasm packages#130764
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Copilot AI commented Jul 15, 2026 •

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Copilot AI commented Jul 15, 2026 •

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