Use more stable hostname for webviews #13092

[jfaltermeier]

What it does

• add optional viewId to WebviewWidgetIdentifier, which may be used to create stable hostnames for webviews
• use this viewId to store a uuid which will be used as part of the stable hostname

For VSCode the WebView iFrame src url looks like this:

vscode-webview://0a7iho5kovpr5p4ctn5fvcns9h4du51vr2fb4iachonmmqsceaes/fake.html?id=ad9dff6c-9d20-4aec-b8b1-edfeecc19d07 (initial open)
vscode-webview://0a7iho5kovpr5p4ctn5fvcns9h4du51vr2fb4iachonmmqsceaes/fake.html?id=faec60d8-1f93-4e66-94b7-931081a8a4ba (close and reopen; restart of application)

In Theia, the pattern was like this:

http://401ed951-431e-4866-9a42-b033d95521d4.webview.localhost:33391/webview/fake.html?id=401ed951-431e-4866-9a42-b033d95521d4 (initial open)
http://837d0c96-f06d-4bad-91ba-efec327876be.webview.localhost:33391/webview/fake.html?id=837d0c96-f06d-4bad-91ba-efec327876be (close and reopen)
http://6444a35c-161b-4205-96b4-a5aee01c0f9e.webview.localhost:37883/webview/fake.html?id=6444a35c-161b-4205-96b4-a5aee01c0f9e (restart of application)

The changing id was used as part of the hostname. Also the port changes between restarts of the electron app.

With this change the src url will look more like this:

http://33544e87-f49c-45eb-b7f7-3387c39fc913.webview.localhost:33391/webview/fake.html?id=401ed951-431e-4866-9a42-b033d95521d4 (initial open)
http://33544e87-f49c-45eb-b7f7-3387c39fc913.webview.localhost:33391/webview/fake.html?id=837d0c96-f06d-4bad-91ba-efec327876be (close and reopen)
http://33544e87-f49c-45eb-b7f7-3387c39fc913.webview.localhost:37883/webview/fake.html?id=6444a35c-161b-4205-96b4-a5aee01c0f9e (restart of application)

In order to fix the port in electron, which is 0 by default so any non-used port, adopers may use the --port option when starting Theia. I think 0 should stay the default.

Fixes #13092

How to test

Webviews should still work as before.
When it comes to testing the storage you may use the reproducer from #13092 and start the electron example either with

• yarn electron start --port=3124
• a custom electron main script, e.g.

process.argv.push('--port=3124')
require('../lib/backend/electron-main.js');

Follow-ups

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[martin-fleck-at]

Change looks good to me, thank you very much Johannes!

I can see that with a fixed port both the session storage and the local storage behave as in VS Code. Without a fixed port, only the session storage behaves as expected and the local storage is cleared. While I understand the technical reasons behind it, I am wondering whether there is a way to also abstract from the port number using a custom scheme as VS Code does or whether this is something we do not even want. In any case, this contribution already provides enough value in itself so it can definitely be merged.

[jfaltermeier]

Thanks. I haven't investigated if we could introduce a custom scheme, but if required at some point we can come back to it.
For the browser version we may want to keep the current scheme though.