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Nothing in the provider harness checks that asking for a flag through the wrong accessor is refused. The evaluator harness checks one row -- wrong-flag as an integer -- and that is the whole of it across both suites. A coerced value is the worst failure mode a flag has: the application receives something plausible and no signal that anything went wrong. Worth asking about directly rather than assuming, because it is not hypothetical. Requesting boolean-flag as a Float through openfeature-flagd-core returns 1.0 with reason STATIC and no error code, and it went unnoticed until a suite asked (open-feature/python-sdk-contrib#417). The same quirk in the integer direction was open-feature/python-sdk#619. Both exist because Python's bool is a subclass of int, so isinstance(True, int) is True and a naive check admits a boolean -- which is exactly the kind of thing one language gets wrong and the others do not. So the two boolean-to-number rows are the point of this, and the rest of the matrix is here because a matrix with holes in it invites the same surprise somewhere else. Numeric coercion is deliberately absent. Whether 0.5 may be narrowed to an integer is unsettled in the specification (open-feature/spec#430), and flagd's own ADR permits coercion when it is lossless, so an integer/float row would assert a rule that does not exist yet. "Is a string a boolean?" needs no such defence, which is the line the OpenFeature provider conformance suite draws in the same matrix (open-feature/spec#423). No new flags: every key used here is already in flags/ and in evaluator/flags/testkit-flags.json. The provider-harness feature is tagged @type-mismatch at the feature level so an implementation that cannot pass it yet can exclude the file and migrate, which is what the tagging scheme in the README is for. Signed-off-by: Simon Schrottner <simon.schrottner@flagsmith.com>
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This repository does not receive automatic reviews because it has fewer than 10 stars. ⚙️ Run configurationConfiguration used: Organization UI Review profile: CHILL Plan: Advanced Run ID: 📝 WalkthroughWalkthroughThe changes add Gherkin coverage for flag type mismatches. Scenarios verify that incompatible accessors return the configured fallback and report ChangesType mismatch coverage
Priority: ⬇️ Low Estimated code review effort: 2 (Simple) | ~10 minutes Change: Other Suggested reviewers: Merge Risk: 🔵 Low · up to The new evaluator scenarios do not verify that a float requested as a string returns the fallback and TYPE_MISMATCH. Add this case before merge to prevent an unchecked coercion regression. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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This was referenced Sep 11, 2026
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In `@evaluator/gherkin/errors.feature`:
- Line 48: Add a String accessor test row for the existing float-flag case in
the relevant Gherkin scenario, expecting TYPE_MISMATCH when the Float value is
coerced to a string; preserve the existing Boolean row.
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The evaluator suite's matrix had three holes the provider suite does not: boolean-flag as String, string-flag as Float, and float-flag as String. CodeRabbit flagged the last of those; the other two are the same oversight. "A matrix with holes in it invites the same surprise somewhere else" is the reason the outline exists at all, so both suites should ask the same questions of the same flags. They now do -- the two row sets are identical. Renames the first Examples block from "requested as a number" to "requested as something else", since it is no longer only numbers. The comment about Python's bool being a subclass of int still applies to the two numeric rows and now says so. No new flags: boolean-flag, string-flag and float-flag are all already in evaluator/flags/testkit-flags.json. Signed-off-by: Simon Schrottner <simon.schrottner@flagsmith.com>
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Nothing in the provider harness checks that asking for a flag through the wrong accessor is refused. The evaluator harness checks one row —
wrong-flagas an integer — and that is the whole of it across both suites.A coerced value is the worst failure mode a flag has: the application receives something plausible and no signal that anything went wrong. This is worth asking about directly rather than assuming, because it is not hypothetical.
gherkin/(provider harness)errors.feature, 11 rowsevaluator/gherkin/errors.featureNo new flags. Every key used here is already in
flags/and inevaluator/flags/testkit-flags.json, so this is scenarios-only and cannot disturb any existing test.The two rows that motivated it
Requesting
boolean-flagas a Float throughopenfeature-flagd-corereturns1.0with reasonSTATICand no error code — open-feature/python-sdk-contrib#417, filed today. The same quirk in the Integer direction was open-feature/python-sdk#619, fixed by open-feature/python-sdk#621.Both exist because Python's
boolis a subclass ofint, soisinstance(True, int)isTrueand a naive check admits a boolean. That is exactly the kind of thing one language gets wrong while the others cannot: Go'sboolis not anint, Java'sBooleanis not aNumber, and TypeScript distinguishes them.The rest of the matrix is here because a matrix with holes in it invites the same surprise somewhere else.
Compatibility — please read before merging
Expect
boolean-flagas aFloatto fail for Python in both harnesses, until open-feature/python-sdk-contrib#417 is fixed. That is the finding rather than a side effect, but it is a real impact on a downstream suite and it is your call how to land it.The provider-harness feature carries
@type-mismatchat the feature level, so an implementation that cannot pass it yet can exclude the file and migrate incrementally — which is what the tagging scheme in the README is for. Everything else is expected to pass: these same assertions already pass against flagd in Go, Java and JavaScript through the OpenFeature provider conformance suite.Numeric coercion is deliberately absent
No integer/float row. Whether
0.5may be narrowed to an integer is unsettled in the specification (open-feature/spec#430), and flagd's own numeric coercion ADR permits coercion when it is lossless — so such a row would assert a rule that does not exist yet."Is a string a boolean?" needs no such defence. That is the same line the OpenFeature provider conformance suite draws in its own version of this matrix (open-feature/spec#423), and the assertions here are deliberately a subset of that one rather than a new rule invented in this repository.
Verification
npm run gherkin-lint, which is what CI runs: clean. It caught one violation on the first attempt (no-background-only-scenario— aBackgroundis not allowed when a feature has a single scenario), fixed by inlining those two steps into the outline.Related