eschutho opened a new pull request, #44802:
URL: https://github.com/apache/superset/pull/44802
### SUMMARY
**Root cause:** `DatabaseRestApi.validate_parameters` (the `POST
/api/v1/database/validate_parameters/` endpoint) catches marshmallow
`ValidationError` and builds `SupersetError` objects by joining the error
messages with `"\n".join(messages)`. However, the field validators in
`superset/databases/schemas.py` — specifically `extra_validator` — raise
`ValidationError` with messages produced by `lazy_gettext()` (imported as `_`),
which returns `LazyString` proxy objects, not native `str` instances.
`str.join()` performs an `isinstance(x, str)` check on each sequence item and
rejects `LazyString`, causing a `TypeError: sequence item 0: expected str
instance, LazyString found`. This turns what should be a clean 422 validation
response into an unhandled 500 for the caller.
One concrete trigger: POSTing `extra` with `{"metadata_cache_timeout":
{"schema_cache_timeout": -1}}` hits the negative-integer validation in
`extra_validator` (~line 343 of `schemas.py`), which raises
`ValidationError([_("The %(key)s in metadata_cache_timeout must be a
non-negative integer.", key=key)])`.
**Fix:** Change `"\n".join(messages)` to `"\n".join(str(m) for m in
messages)` in the `validate_parameters` method. `LazyString.__str__()` resolves
to the translated text, so the resulting message content is identical — the
endpoint just no longer crashes.
### Tradeoffs
This fix does not change any user-visible behavior or semantics. The
resolved message text is identical before and after the fix — it simply no
longer crashes. The only observable change is that a 500 Internal Server Error
becomes the intended 422 validation error response. There is no failure-mode
semantics change to disclose beyond "a 500 becomes the intended 422."
### Follow-up candidates
Grep of the codebase found no other instances of `"\n".join(messages)` over
marshmallow `ex.messages` values. This was the only occurrence of this bug
pattern.
### BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF
Not applicable (API-only change, no UI).
**Before:** `POST /api/v1/database/validate_parameters/` with invalid
`extra.metadata_cache_timeout` returns `500 Internal Server Error` with
`TypeError: sequence item 0: expected str instance, LazyString found`.
**After:** The same request returns `422` with a proper JSON error body
containing the translated validation message.
### TESTING INSTRUCTIONS
1. A new integration test
`test_validate_parameters_extra_metadata_cache_timeout_invalid` was added
alongside the existing `test_validate_parameters_*` tests.
2. The test POSTs a payload with `{"metadata_cache_timeout":
{"schema_cache_timeout": -1}}` in `extra` and asserts the endpoint returns 422
with the expected error structure.
3. **Fail-before evidence:** With the original `"\n".join(messages)` code,
the test fails with `assert 500 == 422` — the server logs show `TypeError:
sequence item 0: expected str instance, LazyString found`.
4. **Pass-after evidence:** With the fix applied (`"\n".join(str(m) for m in
messages)`), the test passes — all 8 `test_validate_parameters_*` tests pass
with no regressions.
5. Ruff check and format pass cleanly on both changed files.
### ADDITIONAL INFORMATION
- [ ] Has associated issue:
- [ ] Required feature flags:
- [ ] Changes UI
- [ ] Includes DB Migration (follow approval process in
[SIP-59](https://github.com/apache/superset/issues/13351))
- [ ] Migration is atomic, supports rollback & is backwards-compatible
- [ ] Confirm DB migration upgrade and downgrade tested
- [ ] Runtime estimates and downtime expectations provided
- [ ] Introduces new feature or API
- [ ] Removes existing feature or API
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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