asWebviewUri: UriError - the path cannot begin with two slash characters

[benc-uk]

• VSCode Version: 1.39
• Local OS Version: Windows 10 Insiders 18995
• Remote OS Version: Ubuntu 18.04
• Remote Extension/Connection Type: WSL and SSH

Steps to Reproduce:

1. Use v0.3.1 of my extension https://marketplace.visualstudio.com/items?itemName=bencoleman.armview in a WSL or SSH VS Code session
2. None of the resources in the webview are loaded, the extension no longer works.
3. I see error Unable to read file (Error: [UriError]: If a URI does not contain an authority component, then the path cannot begin with two slash characters ("//"))

I'm using the webview API
panel.webview.asWebviewUri to form the URLs of the components my WebView needs to load, e.g.

panel.webview.asWebviewUri(vscode.Uri.file(path.join(extensionPath, 'assets', 'css', 'main.css')));

I've been developing this extension for several weeks and work exclusively in WSL remote mode. I've never once had an issue until I updated to version 0.39.9 of the WSL extension (with VS Code 1.39).
Problem does NOT happen when working in local mode

Does this issue occur when you try this locally?: No
Does this issue occur when you try this locally and all extensions are disabled?: No

(Note. I've put a quick fix in the latest version v0.3.2 of my extension, but it's a clumsy hack to load all resources from remote external URL, which isn't a viable solution long term)

[benc-uk]

I can't determine if this is a regression caused by the WSL extension or VS Code itself
I tried running 1.38 of VS Code but that forced me to run an older version of the WSL extension also, making it impossible to pinpoint the cause

I got no problems on 1.38 of VS Code BTW

[benc-uk]

Issue also happens in SSH, not just WSL

I've verified this affects other extensions using a webView and loading resources from the extension folder i.e. using asWebviewUri (i.e. vscode-resource URIs). For example the webview example in the vscode-extension-samples repo is now broken, when I try it under WSL and SSH

For example microsoft/vscode-extension-samples#219

Which provides a simple way to reproduce this issue. Note the cat GIF loads OK, as that's an external HTTP URL, but the JS file referenced from the extension (media directory) doesn't load due to the above error, so the line counter never goes up

[mjbvz]

Duplicate of microsoft/vscode#82336