Extension Development: Failed to load resource: net::ERR_UNKNOWN_URL_SCHEME

[hediet]

• VSCode Version: 1.45.1
• OS Version: Windows 10

Context

Load a resource like so:

const vsuri = webview.asWebviewUri(
  Uri.file(
    path.join(__dirname, "../drawio/src/main/webapp/index.html")
  )
);
webview.html = `...  ${vsuri.toString()} ...`; // this loads something from vsuri

Launch the Extension Development Host VS Code Instance and ensure that it loads this webview on startup.
You can do this by registering a custom editor that uses such a webview and open such a custom editor before closing the Extension Development Host. The next time the Extension Development Host is started, the custom editor will load the webview. This usually (>70% chance) produces the following error:

The Error

Failed to load resource: net::ERR_UNKNOWN_URL_SCHEME

I guess it refers to vscode-resource://.

It only happens on startup, and possibly only in the extension dev host. If I close the the webview and reopen it, it works (this rules out a bug in my extension).

A minimal reproducible extension is some serious work. Others have this same issue.

[hediet]

It actually also happens when bundling the extension and installing it manually, but much less often (like once for 10 refreshes). So it is not a development only issue.

[hediet]

It already happens for the markdown preview feature:

You can see that it did not load the style sheet:

I haven't managed to reproduce it with all extension disabled though. I guess this bug is timing related.

[Speedy37]

Might be fixed by #97777

[hediet]

Ah. Duplicate of #89038.