test(operators): add error return scenarios for custom operator null fallback

[aepfli]

Summary

Adds @operator-errors tagged scenarios to targeting.feature covering error return behavior from flagd#1874.

New Tag

@operator-errors — SDK implementations can opt in to verify their custom operators return null (not false) on error, which triggers the default variant fallback rather than the false branch of a conditional.

New Scenarios

All three scenarios use flags where the targeting rule is a bare operator call (not wrapped in if), so a null return triggers the default variant directly.

sem_ver with unparseable version (semver-invalid-version-flag)

Context passes not-a-version — sem_ver can't parse it, must return null → default variant fallback.

sem_ver with unknown operator (semver-invalid-operator-flag)

Rule uses === which is not a valid sem_ver operator — must return null → default variant fallback.

fractional with missing bucket key (fractional-null-bucket-key-flag)

Context is empty — bucket key variable resolves to null — must return null → default variant fallback.

Related

• flagd#1874 — root bug report
• flagd-evaluator#21 — evaluator tracking issue

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the testing suite by adding comprehensive scenarios for custom operator error handling. The primary goal is to ensure that when custom operators encounter invalid input or conditions, they correctly return a null value, which then triggers the intended default variant fallback. This improves the robustness and predictability of flag evaluation in error conditions.

Highlights

• New Error Handling Scenarios: Introduced new Gherkin scenarios tagged with @operator-errors to specifically test the error return behavior of custom operators.
• Null Fallback Verification: These scenarios verify that SDK implementations correctly return null (instead of false) when custom operators encounter errors, ensuring the default variant fallback mechanism is triggered.
• Specific Test Cases: Added test cases for sem_ver operator with an unparseable version, sem_ver with an invalid operator, and fractional operator with a missing bucket key, all designed to trigger null returns and default variant fallbacks.

Changelog

• flags/edge-case-flags.json
  • Added semver-invalid-version-flag to test sem_ver operator with unparseable version context.
  • Added semver-invalid-operator-flag to test sem_ver operator with an invalid operator.
  • Added fractional-null-bucket-key-flag to test fractional operator with a missing bucket key.
• gherkin/targeting.feature
  • Added a new @operator-errors tagged scenario outline for custom operator error returns and default variant fallback.
  • Added a new @operator-errors tagged scenario for fractional operator with a missing bucket key falling back to the default variant.

Activity

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[gemini-code-assist]

Code Review

This pull request adds test scenarios to verify that custom operators correctly return null on error, leading to the default variant fallback. The changes include new flag definitions in flags/edge-case-flags.json for sem_ver and fractional operator error conditions, and corresponding test scenarios in gherkin/targeting.feature. The implementation looks correct and covers the intended error cases. I've added one suggestion to improve the conciseness of a Gherkin Scenario Outline.

[aepfli]

relates too open-feature/flagd#1874