Fix Test Tool v2 Blazor UI non-interactive on .NET 10 (static assets 404)

[GarrettBeatty]

Symptom

The AWS Lambda Test Tool v2 Blazor web UI had two static-asset serving bugs that broke interactivity, each specific to a target framework:

(A) Non-interactive on .NET 10 (any .NET 9+). Buttons don't respond, @onclick/@bind never fire; window.Blazor is undefined. The tell is subtle — the framework script returns HTTP 200 with a 0-byte body, so status-code checks alone look green while the browser downloads nothing:

# net10, before this fix
_framework/blazor.web.js          -> HTTP 200, 0 bytes      <-- EMPTY
Amazon.Lambda.TestTool.styles.css -> HTTP 200, 0 bytes      <-- EMPTY

(B) Code editor dead on .NET 8 (dotnet run). The Razor class library assets for the Monaco code editor (_content/BlazorMonaco/**) return 404, so the request/response editor never initializes — e.g. selecting an example request does not populate the input, and typing/formatting in the editor doesn't work:

# net8, dotnet run, before this fix
_framework/blazor.web.js                              -> HTTP 200, 187162 bytes  (ok)
_content/BlazorMonaco/lib/monaco-editor/min/vs/loader.js -> HTTP 404, 0 bytes    <-- MISSING

Root cause

Static-asset serving changed in .NET 9: framework assets (_framework/*) and scoped CSS are served by the endpoint-routing app.MapStaticAssets() pipeline, which reads bytes from IWebHostEnvironment.WebRootFileProvider. Under dotnet run, neither the framework files nor RCL _content/** assets physically live in wwwroot — they live in the NuGet cache and are surfaced through the *.staticwebassets.runtime.json manifest. Two things kept that manifest from being reachable:

1. Manifest not composed outside Development. ASP.NET Core only composes the static-web-assets manifest into WebRootFileProvider automatically when the environment is Development (WebHost.ConfigureWebDefaults calls StaticWebAssetsLoader.UseStaticWebAssets only under IsDevelopment()). This tool runs as Production by default, so the web root was a bare wwwroot provider.

   • On net9+ this meant MapStaticAssets served empty (0-byte) 200s for _framework/* → symptom (A).
   • On net8 (no MapStaticAssets), the manifest was likewise never composed, and — see below — nothing read it anyway → symptom (B).

2. Content root followed the current working directory. As an installed global tool the process launches from an arbitrary cwd; WebRootFileProvider defaulted to cwd/wwwroot, a nonexistent path, so every asset returned empty 200s.

3. The classic UseStaticFiles used an explicit bare-wwwroot provider. It was pinned to a PhysicalFileProvider(wwwroot) and never read the manifest-composed WebRootFileProvider. On net9+ this was masked because MapStaticAssets reads WebRootFileProvider; on net8 there is no such reader, so manifest-mapped _content/** assets were unreachable → symptom (B).

Fix

All in Tools/LambdaTestTool-v2/src/Amazon.Lambda.TestTool/Processes/TestToolProcess.cs:

• Pin the content root to the install dir so WebRootFileProvider resolves regardless of launching cwd:

  var builder = WebApplication.CreateBuilder(new WebApplicationOptions
  {
      ContentRootPath = AppContext.BaseDirectory
  });

• Compose the static-web-assets manifest on all target frameworks (previously net9+-only). ASP.NET Core only does this automatically in Development; the tool runs as Production:

  builder.WebHost.UseStaticWebAssets();   // now unconditional

• Serve _framework/* + scoped CSS via the endpoints manifest on net9+:

  #if NET9_0_OR_GREATER
  app.MapStaticAssets();   // guarded: only when the manifest exists (test host has none)
  #endif

• On .NET 8, add a second UseStaticFiles over WebRootFileProvider so manifest-mapped RCL _content/** assets (BlazorMonaco) resolve. There is no MapStaticAssets on net8, and the explicit wwwroot provider can't see the composed manifest:

  #if !NET9_0_OR_GREATER
  if (app.Environment.WebRootFileProvider is not null)
  {
      app.UseStaticFiles(new StaticFileOptions
      {
          FileProvider = app.Environment.WebRootFileProvider
      });
  }
  #endif

The existing wwwroot UseStaticFiles provider is preserved (authoritative for the installed tool, where all assets are published directly into wwwroot). For an installed tool the second net8 lookup resolves to the same wwwroot, so it is a harmless second pass.

Verification — full 8-case matrix

Probed the three assets whose absence breaks the UI — _framework/blazor.web.js (interactive circuit), _content/BlazorMonaco/.../loader.js (Monaco editor → example-request fill), and app.css — asserting HTTP 200 with non-zero bytes across every combination of {.NET 8, .NET 10} × {Production, Development} × {dotnet run, installed tool}:

Case	blazor.web.js	monaco loader.js	app.css	Result
run / net8.0 / Production	200, 187162	200, 30061	200, 3946	✅ PASS
run / net8.0 / Development	200, 187162	200, 30061	200, 3946	✅ PASS
run / net10.0 / Production	200, 200575	200, 30061	200, 3946	✅ PASS
run / net10.0 / Development	200, 200575	200, 30061	200, 3946	✅ PASS
installed / net8.0 / Production	200, 187162	200, 30061	200, 3946	✅ PASS
installed / net8.0 / Development	200, 187162	200, 30061	200, 3946	✅ PASS
installed / net10.0 / Production	200, 200575	200, 30061	200, 3946	✅ PASS
installed / net10.0 / Development	200, 200575	200, 30061	200, 3946	✅ PASS

(Before this change: run/net8.0/* had monaco loader.js -> 404 and run/net10.0/* had blazor.web.js -> 200, 0 bytes.) Real-browser confirmation via headless Chromium: window.Blazor=true and no console errors on /, /documentation, and /durable-execution. Both TFMs build with 0 warnings / 0 errors; the Test Tool unit tests (which invoke Startup directly) pass on net8.

[Copilot]

Pull request overview

Fixes AWS Lambda Test Tool v2’s Blazor UI becoming non-interactive on .NET 9+/net10 by ensuring the .NET 9+ static web assets endpoint pipeline can actually locate and serve framework/scoped-CSS assets regardless of launch working directory and hosting environment.

Changes:

• Pins ASP.NET Core content root to AppContext.BaseDirectory so WebRootFileProvider resolves wwwroot correctly when the tool is launched from an arbitrary cwd (global tool scenario).
• On NET9_0_OR_GREATER, composes static web assets (UseStaticWebAssets) and maps endpoint-based static assets (MapStaticAssets) with a guard to avoid failures when running under a test host.
• Adds an Autover patch changelog entry documenting the fix.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Tools/LambdaTestTool-v2/src/Amazon.Lambda.TestTool/Processes/TestToolProcess.cs	Adjusts hosting options and .NET 9+ static web assets setup so Blazor framework/scoped CSS assets resolve and the UI becomes interactive again.
.autover/changes/156dd8b1-1af2-45fc-b051-b94dc51fc56f.json	Records a patch-level changelog entry for the .NET 9+/net10 static assets/Blazor interactivity fix.

---

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[GarrettBeatty]

also ran manually

[GarrettBeatty]

i retested a second time now manually here is what i did.

Packed and installed the tool to
"~/.dotnet/tools/.store/amazon.lambda.testtool/0.15.0/amazon.lambda.testtool/0.15.0/tools//any/Amazon.Lambda.TestTool.dll

and then for each TFM (net 8/10), i launched the tool with

dev mode
ASPNETCORE_ENVIRONMENT=Development; dotnet start

prod mode (if environment is unset the default is prod as per microsfot docs)

unset ASPNETCORE_ENVIRONMENT; dotnet start

amd then verified in the ui triggering the function it works

[normj]

Given the calls to UseStaticFiles and MapStaticAssets done below is the call still needed?

[GarrettBeatty]

• UseStaticWebAssets() — tells the server where the framework/Monaco files actually are (the NuGet cache, via the manifest). Without it the server looks only in wwwroot, doesn't find them, and
  everything below has nothing to serve. This is the prerequisite for the other two.
• UseStaticFiles(wwwroot) — serves the plain files that do live in wwwroot: app.css, images, favicon. Nothing else serves these, so without it the page loads unstyled.
• MapStaticAssets() (net9+) — on .NET 9+ the framework files (blazor.web.js) and scoped CSS are served through this newer pipeline, not the classic one. Without it they come back empty,
  window.Blazor never loads, and the UI is dead. (.NET 8 has no MapStaticAssets, so a second UseStaticFiles over the manifest-composed provider does the same job.)

tried moving some of the code around and updating the comments to be easier to understand. but i tried testing without all of these options and some scenarios did not work

[GarrettBeatty]

Legend for asset kinds:

• classic = app.css, images, favicon (physically in wwwroot)
• framework = _framework/blazor.web.js + scoped CSS (needed for interactivity)
• RCL = _content/BlazorMonaco/** (needed for the code editor)

Framework	Deployment	classic served by	framework served by	RCL (Monaco) served by	Extra thing that makes it work
net10	dotnet run	UseStaticFiles(wwwroot)	MapStaticAssets()	MapStaticAssets()	UseStaticWebAssets() — files are in the NuGet cache, not wwwroot
net10	installed tool	UseStaticFiles(wwwroot)	MapStaticAssets()	MapStaticAssets()	ContentRootPath pin — tool launches from an arbitrary cwd
net8	dotnet run	UseStaticFiles(wwwroot)	Blazor's own middleware	2nd UseStaticFiles(WebRoot)	UseStaticWebAssets() — files are in the NuGet cache, not wwwroot
net8	installed tool	UseStaticFiles(wwwroot)	Blazor's own middleware	UseStaticFiles(wwwroot)	ContentRootPath pin — everything's in wwwroot, so the base call covers it