fix(eval): default RubricContent.text_property to None so rubrics save without 422

[ALDRIN121]

Summary

Fixes a Pydantic-v2 "required Optional" trap that makes saving an eval case fail with HTTP 422 when a rubric's text_property is omitted or empty.

RubricContent.text_property is typed Optional[str] but has no default. Under Pydantic v2, an Optional field without a default is still required — so when the Web UI's GET serializes an eval case with response_model_exclude_none=True (dropping text_property: None) and the browser re-submits it on the save PUT, the field is missing and validation fails with 422 Unprocessable Entity.

This is the exact same bug class as #6336 / the #6515 fix (fix: make InvocationEvent.content optional so the Web UI can save eval cases), which patched InvocationEvent.content but left RubricContent.text_property unaddressed. Related to #7019 (422 persists across 2.6.0–2.8.0 despite #6515).

Root cause

src/google/adk/evaluation/eval_rubrics.py:

class RubricContent(EvalBaseModel):
  text_property: Optional[str] = Field(
      description="..."          # no default -> Pydantic v2 treats as required
  )

Fix

Default text_property to None, matching the accepted InvocationEvent.content fix:

text_property: Optional[str] = Field(
    default=None,
    description="...",
)

Reproduction (before the fix)

rubric = Rubric(rubric_id="r1", rubric_content=RubricContent(text_property=None))
case = EvalCase(eval_id="c1", conversation=[], rubrics=[rubric])
wire = case.model_dump(by_alias=True, exclude_none=True)  # GET
EvalCase.model_validate(wire)                              # PUT -> ValidationError
# pydantic_core.ValidationError: rubricContent.textProperty — Field required

After the fix, the round-trip succeeds and text_property is None.

Testing plan

• pytest tests/unittests/evaluation/test_eval_case.py — 24 passed (2 new tests: test_rubric_content_text_property_defaults_to_none, test_eval_case_with_rubric_missing_text_property_round_trips).
• pytest tests/unittests/evaluation/test_rubric_based_tool_use_quality_v1.py — passed (no regression in rubric consumers).

Note: I ran the focused evaluation tests; the broader tests/unittests/evaluation/ suite requires optional GCS/Vertex deps not installed in the minimal venv.

Signed-off-by: Aldrin Joseph yoaldrinjoseph@gmail.com

[ALDRIN121]

Hi @i-yliu just following up on #7026 when you get a chance.

This is the small RubricContent.text_property required-Optional fix discovered while investigating #7019. The later #7019 report turned out to be a separate invocationIndex/toolUseIndex issue, but this PR still fixes the independent rubric GET → PUT round-trip failure and includes regression coverage for it.

I’ve kept the change focused. CI currently shows action_required; happy to address anything else needed for review/landing. Thanks!

[ALDRIN121]

Rebased onto current main (044a1ec3); new head is 616093cf. Diff is unchanged: +37/−1 across src/google/adk/evaluation/eval_rubrics.py and tests/unittests/evaluation/test_eval_case.py.

The bug is still live on main. eval_rubrics.py L27 is still text_property: Optional[str] = Field( with no default=None, and that file hasn't been modified since 2026-01-20, so the GET(exclude_none=True) → PUT 422 for a rubric that omits text_property is still reproducible. The sibling fix that landed for #7019 (a4a50a4d, PR #7096) only touched eval_case.py / InvocationEvent; it does not cover this missing-field case.

Issue linkage. The only linked issue, #7019, is now CLOSED (2026-09-16) — it was closed by that separate #7096 fix for the other 422 (UI-only invocationIndex/toolUseIndex extras), which is a different root cause from this one. Per CONTRIBUTING.md ("All PRs ... should have an Issue associated"), this PR currently has no live issue attached. Could you point me at the right issue to link, or I'll open a focused one for the missing text_property default.

Reviewer. @surajksharma07 — you self-assigned #7019 and diagnosed the 422 here; are you the right reviewer for the eval component, or can you redirect me to whoever owns evaluation/?

Post-rebase test run: .venv/bin/python -m pytest tests/unittests/evaluation/test_eval_case.py → 26 passed, 2 warnings in 0.80s (both new tests green).