[kinyoklion]

Summary

Overrides only add to what the SDK reports: a flag that the override layer does not hold must evaluate, and appear in AllFlagsState, as it does without an override source. Three paths broke this. The first two were found while reviewing the same code in the .NET port (dotnet-core #364), the third by the contract tests in launchdarkly/sdk-test-harness#539.

1. AllFlagsState with no LaunchDarkly data and an override source configured. The state was built from the merged read through the overlay, so the flags of a store that is not initialized (a persistent store that holds flags but no init marker) entered it. With an empty layer, that returned a valid state of LaunchDarkly data that the SDK returns as invalid without an override source; with overrides present, the state held those flags alongside the overrides. Without an override source the SDK reports no flags in this state.
2. AllFlagsState when the store read fails. Overlay.GetAll returned the layer's entries alone, with no error, when the base store failed and the layer held entries. An initialized client (daemon mode, for example) whose store fails GetAll then returned a state marked valid with only the override flags and logged nothing. Without an override source, the same failure logs it and returns an invalid, empty state.
3. Evaluation with no LaunchDarkly data and an override source configured. Every key was read through the overlay, so a flag that the layer does not hold fell through to the store, and a store that holds flags but no init marker served them. Without an override source the same evaluation returns the not-ready default.

The fixes:

• The overrides-only state is built from the layer's flags directly, read through a new FDv2.OverrideItems, and only when no LaunchDarkly data is available; a layer without flags still gives an invalid state. Without an override source the SDK reports no flags in this state, so the override flags only add to it.
• Overlay.GetAll returns the base error whatever the layer holds. AllFlagsState is its only caller; per-key Get still serves an override entry without the base. When the store's read fails, AllFlagsState logs the failure as before and returns an invalid state that holds the override layer's flags, and with none it is empty as without a source. flagstate.AllFlagsBuilder gains Valid(bool) so that a state can be invalid and still hold flags. A client-side SDK bootstrapped from the state uses its flags whatever $valid says (js-client-sdk 3.x and the 4.x browser SDK only log a warning), so the overridden values still reach it.
• With no LaunchDarkly data, evaluation reads the flag from the layer itself through a new FDv2.OverrideItem, and a miss returns the not-ready default. Prerequisites and segments are still read through the overlay.

These follow OVERRIDE Requirements 1.2.2 and 1.5.3, and Requirements 1.4.1.2 and 1.4.1.3 proposed in launchdarkly/sdk-specs#280, which replace the sentence in Requirement 1.4.1 that the uninitialized state contains only the overridden flags.

Tests

• ldclient_overrides_test.go, with a persistent store that holds a flag but no init marker and a client that never initializes:
  • an empty override layer gives an invalid, empty state, and a layer with one flag gives a valid state with only that flag;
  • an empty override layer gives the not-ready default for the store's flag, and a layer that holds another flag gives the not-ready default for the store's flag while serving the overridden one.
• ldclient_overrides_test.go, in daemon mode: with an override present, a store read failure gives an invalid state that holds the overridden flag with its marked reason and tracking off, and logs the failure; with no override flags the same failure gives an invalid, empty state.
• interfaces/flagstate/flags_state_test.go: a builder marked invalid keeps its flags and serializes "$valid": false with them.
• internal/overrides/overrides_test.go: the overlay test that pinned the old behavior now asserts that GetAll returns the base error with entries in the layer, while Get still serves the override entry.

Each fix fails its tests when reverted. go test -race ./... passes and make lint reports no issues. The contract tests in launchdarkly/sdk-test-harness#539 fail on v7 and pass on this branch, together with the full Redis persistent data store and flag overrides suites (131 tests).

SDK-3419

_{Opened from termag}

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