feat: Add flag overrides to the contract test service by kinyoklion · Pull Request #454 · launchdarkly/ruby-server-sdk

kinyoklion · 2026-09-25T22:51:32Z

Summary

This PR is stacked on #453 because the test service configures the file-based override source that PR adds.

The contract test service now advertises the flag-overrides capability and accepts the overrides block of the SDK configuration described in the test harness service specification. filePaths, duplicateKeysHandling, changeDetection, and pollIntervalMs map to the options of LaunchDarkly::Integrations::FileData.override_source, which is set on the FDv2 data system builder. An overrides block without a dataSystem block is an error, as in the Go reference service.

The listen gem joins the contract test bundle so that the harness's watching change detection tests can run. The service port can be set with the PORT environment variable and still defaults to 9000, so the existing Makefile and CI steps are unchanged.

Verification against the prebuilt harness (sdk-test-harness branch rlamb/sdk-2657/flag-overrides-tests at 9ad082c, flag-overrides capability): -run 'flag overrides' ran 38 tests with 0 failures, and the full suite with no filter ran 4733 tests with 0 failures (13 skipped by pre-existing capability and long-running gates). The first run of the watching mode tests failed because the watcher relied on listen, which could not scan the system temporary directory where the harness writes its files; the watcher change in #449 corrects that, and both runs above were made with it in place.

The existing FDv1 and FDv2 file data sources keep their current behavior. This series does not change them; the override feature is additive.

SDK-3249

Note

Overview
The Ruby contract test service now supports the harness flag-overrides capability so file-based flag override scenarios can run against this SDK.

When client config includes an overrides block alongside dataSystem, the service maps filePaths, duplicateKeysHandling, changeDetection, and pollIntervalMs onto LaunchDarkly::Integrations::FileData.override_source and attaches it via data_system.overrides. Supplying overrides without dataSystem raises ArgumentError, matching the Go reference service.

The bundle adds the listen gem so watching change-detection tests can run, and the Sinatra app reads PORT (default 9000) for the bind port without changing existing Makefile/CI defaults.

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The test service advertises the flag-overrides capability and accepts the overrides block of the SDK configuration: filePaths, duplicateKeysHandling, changeDetection, and pollIntervalMs map to the options of LaunchDarkly::Integrations::FileData.override_source on the FDv2 data system builder. Overrides without a data system configuration are an error. The listen gem joins the contract test bundle so that the watching change detection mode can run. The service port can be set with the PORT environment variable and still defaults to 9000.

…thout the init key (#539)  ## Summary Overrides only add to what the SDK reports: a flag that the override layer does not hold evaluates as it does without an override source, and the all-flags state holds every flag it holds without one, plus the overridden flags. A client that has not initialized is where SDKs broke this, and only when the store holds flags without being initialized, for example a persistent store that holds data but no init key. The flag overrides suite uses the SDK's in-memory store, which is empty until a data source provides data, so it could not tell a read of the override layer apart from a read of everything the store returns. A new `flag overrides` group in the persistent data store suite (`server_side_persistence_overrides.go`) runs when the test service has the `flag-overrides` capability. It writes flags to the store without the init key and gives the client a data source that never provides data. Each test compares a client with an override source to a client without one against the same store, so it holds whatever an SDK reports for an uninitialized store: - **a flag without an override evaluates as it does without an override source**: an override file that holds a different flag leaves the evaluation of a store flag unchanged (OVERRIDE Requirements 1.5.1 and 1.5.3). - **an empty override source leaves the all-flags state unchanged** (Requirement 1.2.2). - **overrides add to the all-flags state and make it valid**: the state holds exactly the flags of the client without a source, with override values for the overridden keys, plus the flags that exist only in the override layer, and it is valid (launchdarkly/sdk-specs#280, Requirements 1.4.1.2 and 1.4.1.3). The flag overrides suite gains **evaluate all flags returns only the override flags as a valid state** in its uninitialized client group, where the store is empty and every SDK reports only the override flags. ## Results Run with `-enable-persistence-tests` against Redis. | Test service | flag without an override | empty override source | overrides add | |---|---|---|---| | Go `v7` | fails: served from the store | fails: valid state of the store's flags | fails: the store's flags join the overrides | | Go launchdarkly/go-server-sdk#491 | passes | passes | passes | | Node `main` | passes | fails: valid state of the store's flags | passes | | Node launchdarkly/js-core#2132 first commit (`57498a9e`) | passes | passes | fails: drops a store flag the state holds without overrides | | Node launchdarkly/js-core#2132 | passes | passes | passes | | Python (top of the launchdarkly/python-server-sdk#530 stack, sync and async) | passes | passes | passes | | Ruby (top of the launchdarkly/ruby-server-sdk#454 stack) | passes | passes | passes | The Java (launchdarkly/java-core#225) and .NET (`dotnet-server-sdk-v9`) test services do not support persistent stores, so the group skips there; the new uninitialized client test passes on both. The full Redis persistent data store suite and the flag overrides suite pass against Go #491 at `30d4f216` (131 tests run). `golangci-lint` reports no issues. Go and Node fail these tests until launchdarkly/go-server-sdk#491 and launchdarkly/js-core#2132 are merged, for test services whose CI runs the persistent data store suite with this harness version. [SDK-3419](https://launchdarkly.atlassian.net/browse/SDK-3419)   <sub>Opened from termag</sub> [SDK-3419]: https://launchdarkly.atlassian.net/browse/SDK-3419?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ  --- > [!NOTE] > **Overview** > Adds harness coverage for **file flag overrides** when the SDK never initializes but a **persistent store already holds feature data without the `$inited` key**—a case the existing in-memory override suite could not distinguish from “read everything from the store.” > > A new **`flag overrides`** group under the server-side persistent data store suite (`server_side_persistence_overrides.go`, gated on `flag-overrides`) seeds Redis/Consul/Dynamo with flags, uses a blocking unavailable data source, and compares clients with and without override files via `uninitializedClient`. Scenarios assert: store flags not in the override file behave like no override source; an empty override file leaves **evaluate all flags** unchanged; overrides merge into all-flags state, mark it **valid**, and apply override values while retaining other store flags. > > The standalone flag-overrides **`uninitialized client`** group gains **evaluate all flags returns only the override flags as a valid state** (empty store, overrides-only valid state). The persistent suite registers the new group from `server_side_persistence_base.go`. > > <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit 09a8e02. Bugbot is set up for automated code reviews on this repo. Configure [here](https://www.cursor.com/dashboard/bugbot).</sup>

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This was referenced Nov 2, 2026

feat: Add flag override tests for a client whose store holds flags without the init key launchdarkly/sdk-test-harness#539

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fix: Keep overrides through an in-place rewrite of their files #479

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feat: Add flag overrides to the contract test service - #454

feat: Add flag overrides to the contract test service#454
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