rusackas opened a new pull request, #41347:
URL: https://github.com/apache/superset/pull/41347
### SUMMARY
Fixes a white-screen regression where a **partial** `THEME_DEFAULT` (or
`THEME_DARK`) override in `superset_config.py` crashes the frontend.
**Root cause:** PR #35220 populated `THEME_DEFAULT` with ~22 token fields
(`fontFamily`, `colorLink`, etc.). Because Superset loads user config via `from
superset_config import *`, defining `THEME_DEFAULT` in `superset_config.py`
*replaces the entire dict* rather than merging. An operator who sets only a
couple of tokens (e.g. just `colorPrimary`) silently drops all the others. The
frontend then calls `.startsWith()` on an undefined field like `fontFamily` and
dies with a blank white screen.
**The fix:**
1. `superset/config.py` — introduce private `_THEME_DEFAULT_BASE` /
`_THEME_DARK_BASE` constants holding the built-in defaults. The underscore
prefix means they survive `from superset_config import *` (star-imports skip
underscore-prefixed names), so the built-in baseline is always available even
when the operator overrides `THEME_DEFAULT`. `THEME_DEFAULT` / `THEME_DARK` are
aliased to them.
2. `superset/views/base.py` — in `get_theme_bootstrap_data()`, deep-merge
the user's config theme on top of these base constants using the existing
`_merge_theme_dicts()` helper, so unspecified token fields fall back to the
built-in values.
3. `tests/unit_tests/views/test_base_theme_helpers.py` — adds a regression
test (`test_partial_theme_override_preserves_base_tokens`) and updates a few
existing assertions whose expected output legitimately changes now that config
themes are merged with the base.
**Note on a subtle behavior change:** config themes are now **always**
deep-merged over the built-in base — even a full replacement. This is more
correct (you can no longer accidentally drop required tokens), but it does mean
a *deliberately* minimal theme will get base tokens merged back in. Operators
who want to clear a token should set it explicitly rather than omitting it.
### BEFORE/AFTER
**Before:** Setting a partial override in `superset_config.py`, e.g.
```python
THEME_DEFAULT = {"token": {"colorPrimary": "#ff0000"}, "algorithm":
"default"}
```
...renders a blank white screen (`Cannot read properties of undefined
(reading 'startsWith')`).
**After:** The partial override is deep-merged over the built-in defaults.
`/login` and the rest of the app render correctly, with `colorPrimary` applied
and all other tokens (`fontFamily`, `colorLink`, etc.) intact.
### TESTING INSTRUCTIONS
Automated:
```bash
pytest tests/unit_tests/views/test_base_theme_helpers.py -v
```
All 38 tests pass, including the new
`test_partial_theme_override_preserves_base_tokens` regression test.
Manual:
1. Add a partial `THEME_DEFAULT` override (only `colorPrimary`) to
`superset_config.py`.
2. Start Superset and load `/login`.
3. Before this fix: white screen. After: the page renders with the custom
primary color and intact default fonts/tokens.
### ADDITIONAL INFORMATION
- [x] Has associated issue: Fixes #40375
- [ ] Required feature flags:
- [x] Changes UI
- [ ] Includes DB Migration (follow approval process in
[SIP-59](https://github.com/apache/superset/issues/13351))
- [ ] Introduces new feature or API
- [ ] Removes existing feature or API
---
Adopted from
[abdul-haizelabs/superset#6](https://github.com/abdul-haizelabs/superset/pull/6).
Original work by Devin (app/devin-ai-integration) on the Haize Labs fork;
adopted, typing-cleaned, and rebased onto current `master` by @rusackas.
Co-authorship preserved in the commit trailer.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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