Stuck on an issue?

Lightrun Answers was designed to reduce the constant googling that comes with debugging 3rd party libraries. It collects links to all the places you might be looking at while hunting down a tough bug.

And, if you’re still stuck at the end, we’re happy to hop on a call to see how we can help out.

`_framework/blazor-hotreload` 404 when running under subdirectory

See original GitHub issue

Is there an existing issue for this?

I have searched the existing issues

Describe the bug

Please note: This is not the same as the 404 for blazor-hotreload.js, which has been fixed with https://github.com/dotnet/aspnetcore/pull/36897, but this is the second part of https://github.com/dotnet/aspnetcore/issues/35555 which I believe was missed.

The fetch request for _framework/blazor-hotreload from blazor-hotreload.js returns 404 due to the url being relative to the subdirectory, contents of blazor-hotreload.js:

export function receiveHotReload() {
  return BINDING.js_to_mono_obj(new Promise((resolve) => receiveHotReloadAsync().then(resolve(0))));
}

async function receiveHotReloadAsync() {
  const cache = window.sessionStorage.getItem('blazor-webassembly-cache');
  let headers;
  if (cache) {
    headers = { 'if-none-match' : cache.etag };
  }
  const response = await fetch('_framework/blazor-hotreload', { headers });
  if (response.status === 200) {
    const deltas = await response.json();
    if (deltas) {
      try {
        deltas.forEach(d => window.Blazor._internal.applyHotReload(d.moduleId, d.metadataDelta, d.ilDelta));
      } catch (error) {
        console.warn(error);
        return;
      } 
    }
  }
}

Expected Behavior

blazor-hotreload should load successfully and hot reload should work

Steps To Reproduce

Create a hosted ASP.NET Core + Blazor WebAssembly Project
Configure it to operate under a subdirectory (set base href, StaticWebAssetBasePath etc)
Run the hosted project.
Observe that blazor-hotreload.js loads correctly but requests _framework/blazor-hotreload (relative to the subdirectory), breaking hot reload.

Repro: https://github.com/crackalak/BlazorHotReload404