Faster preview on no change, future hot reload

[ScarletKuro]

Fixes #198

Previously, every compilation triggered a full iframe navigation, even when the code hadn’t changed.

Now, if there’s no code change, the preview updates instantly:

(you need to run it with no debugger).

This code also gives some future improvements, once web workers are shipped: dotnet/aspnetcore#65037

CompilationService could run on a worker thread. The pipeline would become:

Editor onChange (debounced ~300ms)
→ Worker thread: CompilationService.CompileAsync()
→ postMessage(dllBytes) back to main thread
→ updateUserComponentsDll + hotReloadIframe
→ iframe: AssemblyLoadContext swap
→ DynamicComponent re-renders

Everything from updateUserComponentsDll downward is already in place. The only missing piece is moving compilation
off-thread.

Rough prototype shape

  // main.js - spawn worker on init
  const compilationWorker = new Worker('compilation-worker.js');

  compilationWorker.onmessage = (e) => {
      if (e.data.type === 'compiled') {
          Try.CodeExecution.updateUserComponentsDll(e.data.dllBytes);
          Try.CodeExecution.hotReloadIframe('user-page-window', '/__main');
      }
  };

  // On editor change (debounced)
  editor.onDidChangeModelContent(debounce(() => {
      compilationWorker.postMessage({ type: 'compile', files: getCurrentFiles() });
  }, 300));

  // compilation-worker.js
  importScripts('dotnet.js'); // hypothetical - load .NET runtime in worker

  onmessage = async (e) => {
      if (e.data.type === 'compile') {
          const dllBytes = await dotnetRuntime.invokeAsync(
              'CompilationService.CompileAsync', e.data.files);
          postMessage({ type: 'compiled', dllBytes });
      }
  };

[ScarletKuro]

I will merge this in few days if nobody else wants to test this manually.
P.S. ignore the failing CI

[versile2]

I have loaded and ran the sample, it ran without issue. I did not look at deep detail of the code as it's so far from dev due to other updates. If you would like me to let me know and I should have time early next week. That being said it seems to work great, recognizes when code has changed etc. One thing I would note is that only the "hot reload" should use that logic, I should be able to click "Play" and cause a relaod so I can handle or test stuff that happens only onafterrender oninit.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud