1900758 - Devtools are not loading and its window pane stays blank

Status: RESOLVED INCOMPLETE

(DevTools :: General, defect)

Description

[Julian Schönbächler]

Attachment: troubleshoot_info.txt

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:126.0) Gecko/20100101 Firefox/126.0

Steps to reproduce:

If I try to open the devtools in Firefox on Windows, the window correctly splits but the devtools never load and the pane stays blank.

1. Open devtools pane via "Browser Tools > Web Developer Tools" or F12 or Ctrl + Shift + I
2. Window pane opens, but stays blank. It can be resized but not closed without also closing the corresponding tab

The issue still occurs when starting Firefox in safe mode. I noticed this issue appearing randomly in the last months on different machines. Sometimes a machine restart fixed it for a short while. But now it happens constantly on all my devices.

Creating a new profile fixes it, so it appears that something has gone wrong with my profile. I already recreated the profile multiple times because of this issue. However, because I like to sync my settings across my devices, every time sync takes over, the problem reoccurs and won't go away.

Starting Firefox with --new-instance --devtools will sometimes load the devtools correctly.

Actual results:

Window pane opens, but stays blank. It can be resized but not closed without also closing the corresponding tab.

Expected results:

Devtools should load successfully.

I really would like continuing to use Firefox as my main development browser. I am in need of assistance to further identify what is causing this issue. It would help tremendously if someone could give me some guidance on how I could further debug or analyze my corrupt profile. Also, steps on how I can completely clear synced settings are greatly appreciated.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Firefox::Sync' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Julian Schönbächler]

Attachment: Opened devtools pane to the right is empty.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:lougenia, could you have a look please?

For more information, please visit BugBot documentation.

Comment 4

[Negritas Sergiu, Desktop QA]

Hello! Thank you for submitting this issue I have tried to reproduce the issue on my end but unfortunately I wasn't able to with firefox 129.0a1(2024-06-12) on Windows 11.
Could you please answer the following questions in order to further investigate this issue?

1. Does this issue happen with a new profile? Here is a link on how to create one: https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles
2. Does this issue happen in the latest nightly? Here is a link from where you can download it: https://www.mozilla.org/en-US/firefox/channel/desktop/
3. Do you have any addons installed? If yes could you please list them?

Comment 5

[Julian Schönbächler]

Hi there, thanks for your time!

1. As already stated in my initial report. It does not happen on a new profile, but as soon as I connect to my Firefox account and sync kicks in, the issue will reappear. I do recognize that my profile has somehow gone corrupt, but I'm unable to fix this. It seems I have to completely delete and recreate my account in order to purge the online cache of my profile settings.
2. I tested with the linked beta version (128.0b9) and the issue persists.
3. Yes many. However, the issue persists in safe mode. Following extensions are installed:

• Firefox Multi-Account Container
• uBlock Origin
• User-Agent Switcher and Manager
• Cookie AutoDelete
• Decentraleyes
• Bitwarden Password Manager
• Bypass Paywalls Clean
• Open in VLC™ media player
• Special Characters
• Vue.js devtools
• Web Archives

Comment 6

[Julian Schönbächler]

Attachment: Issue persist in Firefox Nightly 129.0a1 (empty devtools pane to the right)

I quickly tested with the suggested Firefox Nightly version 129.0a1 and the issue persist. I can open the devtools pane without any problems but as soon as I sync the browser with my Firefox Account, the issue reappears.

Comment 7

[Julian Descottes [:jdescottes]]

Thanks for the report!

Could you check the Browser Console logs when the issue occurs and attach them here? https://firefox-source-docs.mozilla.org/devtools-user/browser_toolbox/index.html

Also can you share if you have the issue when opening DevTools on any webpage, or is it just with a specific one?

Thanks

Comment 8

[Julian Schönbächler]

Ok, something changed.
First of all, I tried to enable the browser toolbox, but because of the devtools panel not loading, I couldn't find a way to access the settings.
Also yes, the issue appeared on any page, even the default "new tab" page of Firefox.

However an update: the issue fixed itself and I now can no longer recreate the problem. I try to list, what I think did the trick.
As I was getting increasingly frustrated with this issue, I started to undo every customization I possibly did to my browser. I knew it must have something to do with a setting that gets synced, as the issue only appears after I connect to my Firefox Account. So, I reinstalled Firefox, enabled Sync and let it synchronize all my settings. After that I restarted the browser and one-by-one reverted all my settings and uninstalled all add-ons (with enabled sync), trying to fully clean the synced settings. The only extension I had left was Firefox Multi-Account Containers. The issue still persisted and I could not open the devtools pane.

So then I remembered; there was a time in an earlier version where the list of container tabs was not yet reorderable through the UI. One had to change the containers.json file in the profile directory manually and change the array order of the identities key. My containers.json looked like this:

{
    "version": 5,
    "lastUserContextId": 8,
    "identities": [
        {
            "userContextId": 1,
            "public": true,
            "icon": "fingerprint",
            "color": "blue",
            "name": "Personal"
        },
        {
            "userContextId": 2,
            "public": true,
            "icon": "briefcase",
            "color": "green",
            "name": "Work"
        },
        {
            "userContextId": 3,
            "public": true,
            "icon": "pet",
            "color": "yellow",
            "name": "Entertainment"
        },
        {
            "userContextId": 4,
            "public": true,
            "icon": "dollar",
            "color": "red",
            "name": "Banking"
        },
        {
            "userContextId": 5,
            "public": true,
            "icon": "cart",
            "color": "turquoise",
            "name": "Shopping"
        },
        {
            "userContextId": 6,
            "public": true,
            "icon": "fence",
            "color": "toolbar",
            "name": "Fenced"
        },
        {
            "userContextId": 7,
            "public": true,
            "icon": "chill",
            "color": "purple",
            "name": "Private"
        },
        {
            "userContextId": 4294967295,
            "public": false,
            "icon": "",
            "color": "",
            "name": "userContextIdInternal.webextStorageLocal"
        },
        {
            "userContextId": 4294967296,
            "public": false,
            "icon": "",
            "color": "",
            "name": "userContextIdInternal.thumbnail"
        }
    ]
}

userContextIdInternal.thumbnail struck me as its userContextId looks like an invalid value (32-bit integer overflow). Well, I just deleted the whole file, let Firefox generate a new one, removed all the custom containers from the settings and let it synchronize. After that I re-added my custom containers (in Firefox, I didn't touch the containers.json anymore), and suddenly my devtools issue is gone and the pane loads successfully again.

Tough, the funny thing is that it seems I cannot force the issue to appear again. Even if I replace the containers.json to the old, possible corrupt file, it won't break. This leaves me somewhat unsure if it really was a Firefox Multi-Account Containers issue or if the complete reset of all my settings changed something else.

That's that. I appreciate all your help and debugging advice and the time investment of everyone involved.

Comment 9

[Julian Descottes [:jdescottes]]

Thanks a lot for the detailed investigation! We don't really know why containers would be clashing with the devtools startup, but since you can no longer reproduce the issue let's close this as WORKSFORME for now. But if you happen to reproduce the issue, please reopen this, we would really like to investigate this if you can trigger it again.

Regarding the browser toolbox, note that alternatively you can use -console as a command line argument to get more logs when starting firefox.
If needed there are also preferences you can manually set to enable the browser toolbox, so we might still have a way to enable it.

Comment 10

[Julian Schönbächler]

Attachment: console-export-2024-7-12_2-47-27.txt

I was able to reproduce the problem on Firefox Nightly version 129.0a1. I attached the extracted console log.

Comment 11

[Julian Descottes [:jdescottes]]

Thanks a lot for the logs!

We should be able to add a check around https://searchfox.org/mozilla-central/rev/8c6edfe25c094e032a27722ef30f69555f556bf8/devtools/server/connectors/js-process-actor/target-watchers/window-global.sys.mjs#167

const childWindow = browser.browsingContext.window;

but before that, it would be great to have a test case to reproduce this and avoid regressions.
How did you manage to get the issue again, do you have steps to reproduce?

Comment 12

[BugBot [:suhaib / :marco/ :calixte]]

A needinfo is requested from the reporter, however, the reporter is inactive on Bugzilla. Given that the bug is still UNCONFIRMED, closing the bug as incomplete.

For more information, please visit BugBot documentation.