fix: prevent 500 error on partial update of multivariate options by srijantrpth · Pull Request #8309 · Flagsmith/flagsmith

srijantrpth · 2026-08-15T16:43:54Z

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Changes

Resolved an issue where partially updating a multivariate option via a PATCH request returned a 500 Internal Server Error when omitting fields like default_percentage_allocation or feature.

Updated MultivariateFeatureOptionSerializer.validate() and _validate_key_is_unique() in api/features/multivariate/serializers.py to safely extract these fields using .get() and fallback to self.instance values, preventing the unhandled KeyError.

How did you test this code?

Added a unit test (test_partially_updating_multivariate_option_success) in api/tests/unit/features/multivariate/test_unit_multivariate_views.py to verify that sending a PATCH request with only the key field correctly returns a 200 OK and preserves the existing default_percentage_allocation without throwing an error. Tested successfully via pytest.

vercel · 2026-08-15T16:43:59Z

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coderabbitai · 2026-08-15T16:44:19Z

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api/tests/unit/features/multivariate/test_unit_multivariate_views.py

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📝 Walkthrough

Walkthrough

The serializer now supports partial updates for multivariate feature options. It uses existing instance values when PATCH data omits the feature or allocation. Key uniqueness validation also uses the existing feature. A view test covers a partial key update and confirms that the percentage allocation remains unchanged.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 34efb

This change prevents partial multivariate-option updates from returning a 500 error while preserving existing values; no actionable merge-blocking risk remains after normal checks and review.

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Actionable comments posted: 2

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api/features/multivariate/serializers.py
api/tests/unit/features/multivariate/test_unit_multivariate_views.py

coderabbitai · 2026-08-15T16:48:06Z

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♻️ Duplicate comments (2)

api/features/multivariate/serializers.py (1)

148-149: ⚠️ Potential issue | 🟠 Major

Resolve the existing key before applying this feature fallback.

When a PATCH changes feature but omits a non-null key, _validate_key_is_unique returns at Lines 145-147 before Lines 148-149 run. The existing key is not checked against the destination feature. This can violate unique_together = ("feature", "key") and produce a 500 instead of a serializer validation error. Resolve key from attrs or self.instance before the None check, and add a feature-only conflicting-key regression test.

This is based on the uniqueness contract in api/features/multivariate/models.py and the writable feature PATCH path in api/features/multivariate/views.py.

api/tests/unit/features/multivariate/test_unit_multivariate_views.py (1)

137-137: ⚠️ Potential issue | 🟡 Minor

Add the final newline.

Ruff 0.16.1 reports W292 at Line 137. Add a newline at the end of api/tests/unit/features/multivariate/test_unit_multivariate_views.py.

Source: Linters/SAST tools

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api/features/multivariate/serializers.py
api/tests/unit/features/multivariate/test_unit_multivariate_views.py

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codecov · 2026-08-15T17:04:02Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.64%. Comparing base (a013d7b) to head (b3b8004).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8309      +/-   ##
==========================================
- Coverage   98.78%   98.64%   -0.14%     
==========================================
  Files        1604     1604              
  Lines       64335    64344       +9     
==========================================
- Hits        63551    63470      -81     
- Misses        784      874      +90

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khvn26 · 2026-08-16T12:21:25Z

Hello @srijantrpth, thanks for your contribution.

Can you fix the remaining linting error?

flagsmith-lint-tests.....................................................Failed
- hook id: flagsmith-lint-tests
- exit code: 1

api/tests/unit/features/multivariate/test_unit_multivariate_views.py:111:1: FT003 Test name `test_partially_updating_multivariate_option_success` doesn't match `test_{subject}__{condition}__{expected}` (found 1 parts, expected 3)

srijantrpth · 2026-08-16T12:46:03Z

Hi @khvn26 , Thanks for the review! I just pushed a commit to fix that linting error by renaming the test to match the required test_{subject}underscore underscore{condition}underscore underscore {expected} convention. Let me know if everything looks good now!

khvn26 · 2026-08-16T14:29:18Z

+    url = reverse(
+        "api-v1:projects:feature-mv-options-detail",
+        args=[project.id, multivariate_feature.id, mv_option.id],
+    )


Can we use a compiled url here? See here.

Sorry. See the url variable in test_list_mv_options__feature_in_other_project__returns_404 as an example.

Hey @khvn26, I think the link you added for 'here' might be broken it just loops me back to this exact comment! Could you share the link to the example you meant to show me so I can get this updated?

Ah, got it! Thanks for pointing me to that example. I've updated it to use the f-string URL pattern.

fix: prevent 500 error on partial update of multivariate options

ad13fa6

srijantrpth requested a review from a team as a code owner August 15, 2026 16:43

srijantrpth requested review from khvn26 and a lite review from Copilot and removed request for a team August 15, 2026 16:43

Copilot AI reviewed Aug 15, 2026

github-actions Bot added the api Issue related to the REST API label Aug 15, 2026

coderabbitai Bot reviewed Aug 15, 2026

View reviewed changes

Comment thread api/features/multivariate/serializers.py Outdated

Comment thread api/tests/unit/features/multivariate/test_unit_multivariate_views.py Outdated

Merge branch 'main' into fix-8306-partial-update-multivariate

dfa23f7

[pre-commit.ci] auto fixes from pre-commit.com hooks

6c97df2

for more information, see https://pre-commit.ci

coderabbitai Bot reviewed Aug 15, 2026

View reviewed changes

srijantrpth and others added 2 commits August 15, 2026 16:56

Fix mypy Testing errors and Key Extraction

461a720

[pre-commit.ci] auto fixes from pre-commit.com hooks

eb5081f

for more information, see https://pre-commit.ci

style: rename multivariate test to match linting conventions

34efb5b

khvn26 reviewed Aug 16, 2026

View reviewed changes

test: use compiled url string for mv option patch test

b3b8004

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srijantrpth commented Aug 15, 2026

Changes

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