[6.1.0rc3] Bug in the "Dark" theme (?)

[herve-lg]

Bug description

I think there is a problem in version 6.1.0rc3: when I switch to the "Dark" theme, my screen becomes completely black and contains no objects.

There seems to be an error of the type "Cannot read properties of undefined (reading 'startsWith')." Maybe we should plan for a case where the script expected at the beginning of the code might be missing?

As for the rest, version 6.1.0rc3 improves the UX even more and solves some bugs present in 6.1.0 and 6.1.0rc2. Congratulations on your work!

Screenshots/recordings

No response

Superset version

master / latest-dev

Python version

3.11

Node version

18 or greater

Browser

Chrome

Additional context

I think there is a problem in version 6.1.0rc3: when I switch to the "Dark" theme, my screen becomes completely black and contains no objects.

As for the rest, version 6.1.0rc3 improves the UX even more and solves some bugs in 6.1.0 and 6.1.0rc2. Congratulations on your work !

Checklist

• I have searched Superset docs and Slack and didn't find a solution to my problem.
• I have searched the GitHub issue tracker and didn't find a similar bug report.
• I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.

[dosubot]

This appears to be the same issue reported by others on 6.1.0rc2 [1] — the "Cannot read properties of undefined (reading 'startsWith')" error is actually caused by the LanguagePicker component crashing during app initialization, which prevents the entire UI from rendering (hence the black screen). It's not specific to the Dark theme itself.

The root cause is that LanguagePicker.tsx accesses languages[locale].flag without null checking [2]. When the LANGUAGES variable in superset_config.py is missing or the locale key doesn't match (the backend can strip territory codes, e.g. zh_TW → zh), the lookup returns undefined and the app crashes.

Workaround: Ensure your superset_config.py has a properly configured LANGUAGES dict with matching locale keys, e.g.:

LANGUAGES = {
    "en": {"flag": "us", "name": "English"},
}

Setting BABEL_DEFAULT_LOCALE = "en" can also help avoid the mismatch.

Fix: PR #39585 adds optional chaining (languages[locale]?.flag ?? '') to prevent this crash, but it hasn't been merged yet, which is why 6.1.0rc3 is still affected.

To reply, just mention @dosu.

---

Docs are dead. Just use Dosu.

[herve-lg]

I can’t figure out where the problem is coming from. I removed from the superset_config.py file the "languages" that were not integrated into my Superset build. I uninstalled and reinstalled Superset.

I still have the same black page for the "Dark" theme.

Here are the console messages:

"
TypeError: Cannot read properties of undefined (reading 'startsWith')
at n (616.94c331d4202698eb2aa9.entry.js:8:21553)
at es (8085.4bc9b7059e85ba458bcb.entry.js:735:950)
at ii (vendors.6f4ecbc3d2e23e236060.entry.js:550:51407)
at c (vendors.6f4ecbc3d2e23e236060.entry.js:554:21698)
at a3 (vendors.6f4ecbc3d2e23e236060.entry.js:554:872)
at a4 (vendors.6f4ecbc3d2e23e236060.entry.js:554:742)
at aY (vendors.6f4ecbc3d2e23e236060.entry.js:552:11364)
at aq (vendors.6f4ecbc3d2e23e236060.entry.js:552:8686)
at lg (vendors.6f4ecbc3d2e23e236060.entry.js:554:19014)
at vendors.6f4ecbc3d2e23e236060.entry.js:554:20399
i2 @ vendors.6f4ecbc3d2e23e236060.entry.js:552

Unhandled error during app initialization TypeError: Cannot read properties of undefined (reading 'startsWith')
at n (616.94c331d4202698eb2aa9.entry.js:8:21553)
at es (8085.4bc9b7059e85ba458bcb.entry.js:735:950)
at ii (vendors.6f4ecbc3d2e23e236060.entry.js:550:51407)
at c (vendors.6f4ecbc3d2e23e236060.entry.js:554:21698)
at a3 (vendors.6f4ecbc3d2e23e236060.entry.js:554:872)
at a4 (vendors.6f4ecbc3d2e23e236060.entry.js:554:742)
at aY (vendors.6f4ecbc3d2e23e236060.entry.js:552:11364)
at aq (vendors.6f4ecbc3d2e23e236060.entry.js:552:8686)
at lg (vendors.6f4ecbc3d2e23e236060.entry.js:554:19014)
at vendors.6f4ecbc3d2e23e236060.entry.js:554:20399
(anonymous) @ spa.75f58c053056fc51f1b6.entry.js:306

Service Worker registration failed: TypeError: Failed to register a ServiceWorker for scope ('https://xxx.xxxxxx.xx/static/') with script ('https://xxx.xxxxxx.xx/static/service-worker.js'): A bad HTTP response code (404) was received when fetching the script.
(anonymous) | @ | welcome/:106
"

[krmmkr]

I have faced a similar issue when defining the default / dark theme config in superset_config.py
It works fine and have no issues when I comment out out the theme config in superset config.
However creating new theme in UI works fine for me

[herve-lg]

@krmmkr You saved me! It was exactly the same problem. The simple fact of adding the token "brandLogoUrl" to my file "superset_config.py" crashes the "dark" theme. Commenting on it, this solves the problem:

THEME_DARK = { "token": { # "brandLogoUrl": "/static/assets/images/dark_logo_odt.svg", }, "algorithm": "dark", }

Thank you @krmmkr!

That said, there must be a problem in the Superset code to solve?