fix(multi): map FLAG_NOT_FOUND and TARGETING_KEY_MISSING to ErrorReason

[chiliec]

Closes #560.

Problem

In openfeature/multi/isolation.go, toProviderResolutionDetail maps two error codes to reasons that assert success:

• FlagNotFoundCode → of.DefaultReason
• TargetingKeyMissingCode → of.TargetingMatchReason (a targeting match reported as the reason for a missing targeting key)

Every other error code in the switch maps to of.ErrorReason.

Fix

Map both to of.ErrorReason. Per spec requirement 1.4.9, in cases of abnormal execution the reason field SHOULD indicate an error.

Tests

Added Test_toProviderResolutionDetail_ErrorCodesMapToErrorReason — a table test asserting every error code produces ErrorReason and a non-nil Error().

Validation:

make mockgen
go test -tags testtools -race ./openfeature/multi/
ok  	github.com/open-feature/go-sdk/openfeature/multi	1.297s
go vet -tags testtools ./openfeature/multi/   # clean

Confirmed RED before the fix (the flag not found and targeting key missing subtests failed with expected: "ERROR") and GREEN after.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

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Plan: Advanced

Run ID: b4d64ab7-4928-4916-a960-3167f86fbf6f

📥 Commits

Reviewing files that changed from the base of the PR and between 8f9f17d and 62b392d.

📒 Files selected for processing (2)

• openfeature/multi/isolation.go
• openfeature/multi/isolation_test.go

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📝 Walkthrough

Walkthrough

The change maps FlagNotFoundCode and TargetingKeyMissingCode to of.ErrorReason. Table-driven tests cover six error codes and verify that each produces an error.

Changes

Resolution error reason mapping

Layer / File(s)	Summary
Error reason mapping and validation openfeature/multi/isolation.go, openfeature/multi/isolation_test.go	FlagNotFoundCode and TargetingKeyMissingCode now use of.ErrorReason. Tests cover six error codes and verify error results.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: toddbaert

Merge Risk: ⚪ Minimal · up to 62b39

The targeted error-reason mappings and regression coverage align with the intended behavior, so the change is ready to merge.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the main change: mapping FLAG_NOT_FOUND and TARGETING_KEY_MISSING to ErrorReason.
Description check	✅ Passed	The description directly explains the incorrect mappings, the fix, the specification basis, and the added validation for the changeset.
Linked Issues check	✅ Passed	Issue #560 requires FlagNotFoundCode and TargetingKeyMissingCode to map to of.ErrorReason. The PR summary states that openfeature/multi/isolation.go applies of.ErrorReason to both cases. The…
Out of Scope Changes check	✅ Passed	The reported changes are limited to the two reason mappings in openfeature/multi/isolation.go and focused table-driven tests in openfeature/multi/isolation_test.go. These changes directly support …

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