Theia breaks when multiple instances are opened

[ReasonSharp]

Bug Description:

When opening multiple instances of Theia (i.e. one for the backend and one for the frontend project), the first opened instance breaks - many functionalities stop working. The ones I noticed are search for references to methods (the references list opens but is empty even though there are references to the method), and the about window doesn't open.

Steps to Reproduce:

1. Start up the system.
2. Open first instance of Theia (on my machine a workspace opens automatically on Theia startup, this could be relevant; also, I'm running Theia using the AppImage).
3. Open second instance of Theia (no workspace opens in this instance).
4. Select a different workspace to work on in the second instance.
5. Go back to first instance and search for references to a method you know you use.
6. Try opening the About window from the Help menu.

Workaround

After step 4 above, close first instance of Theia and open a new one. There open the workspace that was opened originally in the first instance. Both instances of Theia should now work properly.

Additional Information

• Operating System: Debian 12 (Bookworm), Gnome desktop
• Theia Version: 1.55.0
• VS Code API Version: 1.94.2

Extensions I use (if relevant):

@theia/ai-chat 1.55.0
@theia/ai-chat-ui 1.55.0
@theia/ai-code-completion 1.55.0
@theia/ai-core 1.55.0
@theia/ai-history 1.55.0
@theia/ai-llamafile 1.55.0
@theia/ai-ollama 1.55.0
@theia/ai-openai 1.55.0
@theia/ai-terminal 1.55.0
@theia/ai-workspace-agent 1.55.0
@theia/bulk-edit 1.55.0
@theia/callhierarchy 1.55.0
@theia/collaboration 1.55.0
@theia/console 1.55.0
@theia/core 1.55.0
@theia/debug 1.55.0
@theia/dev-container 1.55.0
@theia/editor 1.55.0
@theia/editor-preview 1.55.0
@theia/electron 1.55.0
@theia/external-terminal 1.55.0
@theia/file-search 1.55.0
@theia/filesystem 1.55.0
@theia/getting-started 1.55.0
@theia/keymaps 1.55.0
@theia/markers 1.55.0
@theia/memory-inspector 1.55.0
@theia/messages 1.55.0
@theia/metrics 1.55.0
@theia/mini-browser 1.55.0
@theia/monaco 1.55.0
@theia/navigator 1.55.0
@theia/notebook 1.55.0
@theia/outline-view 1.55.0
@theia/output 1.55.0
@theia/plugin-dev 1.55.0
@theia/plugin-ext 1.55.0
@theia/plugin-ext-vscode 1.55.0
@theia/preferences 1.55.0
@theia/preview 1.55.0
@theia/process 1.55.0
@theia/property-view 1.55.0
@theia/remote 1.55.0
@theia/scm 1.55.0
@theia/search-in-workspace 1.55.0
@theia/secondary-window 1.55.0
@theia/task 1.55.0
@theia/terminal 1.55.0
@theia/test 1.55.0
@theia/timeline 1.55.0
@theia/toolbar 1.55.0
@theia/typehierarchy 1.55.0
@theia/userstorage 1.55.0
@theia/variable-resolver 1.55.0
@theia/vsx-registry 1.55.0
@theia/workspace 1.55.0
theia-ide-launcher-ext 1.55.0
theia-ide-product-ext 1.55.0
theia-ide-updater-ext 1.55.0

[JonasHelming]

@tsmaeder

[tsmaeder]

This sounds a lot like we're really starting a second electron process. In Theia IDE, this should not happen, we should be opening a second window for the first started instance.
@ReasonSharp are you using Theia IDE as downloaded from the Eclipse page or are you building your own application?

[ReasonSharp]

@tsmaeder I'm just using Theia IDE, not building. As I said, I'm just using the AppImage.

[sdirix]

I tried reproducing the problem with the Theia IDE 1.55 AppImage but was unable to do so. I'm on Ubuntu.

Can you check whether you have any error messages in the logs, for example in the Developer Tools? You can also start the AppImage via terminal and check the output there.

[ReasonSharp]

@sdirix after having reproduced it a couple of times when making this report, I was not able to reproduce it again until it happened while I was working on something.

It appears to only happen with the instance where I have an Angular app opened, but now I'm completely confused as to the conditions under which it happens. I'll keep trying to figure it out.

[sdirix]

@ReasonSharp Were you able to reproduce in the mean time? If not, are you fine with closing the issue for now?

[ReasonSharp]

@sdirix I wasn't able to get this to happen again so as to be reproducible, though it still only happens with the Angular app, and now only occasionally.

Since I can't be sure what's causing it I suppose this can be closed.