Multiple instances of Theia breaks VScode extensions with webview.

[emilhammarstedtst]

Bug Description:

If two theia instances are open at the same time only the first opened theia will be able to show a webview. the second and third will get an error.

Steps to Reproduce:

1. start two instances of Theia (Electron)
2. start a vscode-extension that uses a webview in both Theia instances
3. The webview will only render in the first instance.
   

Additional Information

• Operating System: Only confirmed on Windows yet
• Theia Version: 1.22.0
• Only Electron is affected

[emilhammarstedtst]

The error originates from: ./packages/plugin-ext/src/main/browser/webview/pre/host.js:70
Uncaught (in promise) DOMException: Failed to register a ServiceWorker: The document is in an invalid state.

[tsmaeder]

And by "two instances" you mean two windows using the same back-end process?

[emilhammarstedtst]

And by "two instances" you mean two windows using the same back-end process?

Two electron instances with one separate back-end processes each

[mbilal100]

In my case, same issue can also be reproduce by launch the 'extensionHost' for webview debugging.
So basically debugging of webveiw extension is not possible within Theia.
Steps to Reproduce:

• Create webview extension
• Add extensionHost launch type in launch.json
• Launch "Run Extension" or press F5
• execute webveiw command result Uncaught (in promise) DOMException: Failed to register a ServiceWorker: The document is in an invalid state.