Add native FF&E configuration flow for React Native

[leoromanovsky]

Motivation

We need a React Native delivery path for offline initialization and dynamic configuration that can move quickly for a customer evaluation without first landing, reviewing, releasing, and consuming upstream iOS and Android SDK changes. This branch keeps the implementation native-first: React Native exposes the RFC-shaped rules/offline configuration API surface, while Kotlin and Swift own configuration parsing, evaluator state, rules fetch, persistence, and SDK side effects in RN-local code that can later be extracted into the iOS and Android SDKs.

Changes

• Adds the native rules/offline configuration API surface in React Native: parse/serialize config wire, fetch rules config, save/load, explicit activation, dynamic context, typed evaluations, and debug state.
• Implements RN-local Kotlin and Swift UFC evaluators that parse configuration once into native models and evaluate from native state, avoiding JSON deserialization on every flag evaluation.
• Reuses existing native Flags SDK side-effect hooks for exposures, flag-evaluation EVP emission, and RUM feature-flag annotation instead of adding a JS side-effect pipeline.
• Adds shared ffe-system-test-data parity tests plus a new-architecture Android smoke that runs the offline corpus from React Native JS through the native bridge in CI.

Decisions

• Phase 1 is RN-local but native-first so React Native can move now, while the Kotlin/Swift pieces remain shaped for later extraction into the iOS and Android SDKs.
• The existing DdFlags / FlagsClient / DatadogOpenFeatureProvider precompute client remains unchanged; this PR adds a separate rules/offline path.
• Fetch and load are intentionally non-mutating. Active evaluation state changes only through explicit setConfiguration.
• Shared fixtures are the cross-repo correctness contract for this branch and the future iOS/Android extraction.

React Native API Example

import {
  CoreConfiguration,
  DdSdkReactNative,
  TrackingConsent,
} from '@datadog/mobile-react-native';

const sdkConfig = new CoreConfiguration(
  '<client-token>',
  'staging',
  TrackingConsent.GRANTED,
  {
    rumConfiguration: {
      applicationId: '<rum-application-id>',
    },
  },
);

await DdSdkReactNative.initialize(sdkConfig);

// Offline initialization from a bundled rules ConfigurationWire string.
const offlineConfig = await DdSdkReactNative.configurationFromString(
  bundledRulesConfigurationWire,
);
await DdSdkReactNative.setConfiguration(offlineConfig);

await DdSdkReactNative.setEvaluationContext({
  targetingKey: user.id,
  attributes: {
    plan: user.plan,
  },
});

const checkoutEnabled = await DdSdkReactNative.resolveBooleanEvaluation(
  'checkout.enabled',
  false,
);

// Later, refresh the rules config without changing active evaluation state.
const previousWire = await DdSdkReactNative.configurationToString(offlineConfig);
const fetchedConfig = await DdSdkReactNative.fetchRulesConfiguration({
  endpoint: 'https://app.datadoghq.com/api/v2/feature-flagging/config/rules-based',
  headers: {
    'dd-client-token': '<client-token>',
  },
  flagQueryParams: {
    dd_env: 'staging',
  },
  previousConfigurationWire: previousWire,
});

await DdSdkReactNative.saveConfiguration(fetchedConfig, {slot: 'default'});

// Activate the refreshed config only when the app is ready to switch.
await DdSdkReactNative.setConfiguration(fetchedConfig);

// Evaluations after activation use the refreshed rules config and current context.
const refreshedCheckoutEnabled = await DdSdkReactNative.resolveBooleanEvaluation(
  'checkout.enabled',
  false,
);

Flow

flowchart TB
  RN[React Native app] --> API[New native rules/offline config APIs]
  API --> Kotlin[Kotlin RN-local FF&E core]
  API --> Swift[Swift RN-local FF&E core]
  Kotlin --> ParsedK[Parsed UFC model]
  Swift --> ParsedS[Parsed UFC model]
  Kotlin --> NativeSDK[Existing native Flags SDK hooks]
  Swift --> NativeSDK
  NativeSDK --> EVP[EVP exposures and flag evaluations]
  NativeSDK --> RUM[RUM feature-flag annotations]
  Kotlin -. later extract .-> AndroidSDK[Android SDK library]
  Swift -. later extract .-> IosSDK[iOS SDK library]

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sequenceDiagram
  participant JS as React Native JS
  participant Bridge as Native bridge
  participant Core as Native FF&E core
  participant HTTP as Rules config API
  participant Disk as Native storage

  JS->>Bridge: configurationFromString(bundled wire)
  Bridge->>Core: parse UFC once
  JS->>Bridge: setConfiguration(config)
  JS->>Bridge: setEvaluationContext(context A)
  JS->>Bridge: resolve*Evaluation(flag, default)
  Bridge-->>JS: value, reason, metadata
  JS->>Bridge: setEvaluationContext(context B)
  JS->>Bridge: resolve*Evaluation(flag, default)
  JS->>Bridge: fetchRulesConfiguration(options)
  Bridge->>HTTP: GET rules-based config
  HTTP-->>Bridge: ConfigurationWire
  Bridge-->>JS: fetched config, active state unchanged
  JS->>Bridge: saveConfiguration(fetched config)
  Bridge->>Disk: persist wire
  JS->>Bridge: setConfiguration(fetched config)
  JS->>Bridge: resolve*Evaluation(flag, default)

Loading

flowchart LR
  CI[test:native-android] --> Metro[Metro]
  CI --> Emulator[Android emulator]
  Metro --> App[New architecture example app]
  Emulator --> App
  App --> Runner[offline fixture runner]
  Runner --> Bridge[RN bridge]
  Bridge --> Core[Kotlin native FFE core]
  Core --> Result[233 shared fixture cases pass]

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Validation

• yarn tsc -p example-new-architecture/tsconfig.json --noEmit
• yarn run lint passes with 0 errors and the existing 10 warnings.
• ANDROID_HOME=/opt/homebrew/share/android-commandlinetools ANDROID_SDK_ROOT=/opt/homebrew/share/android-commandlinetools JAVA_HOME=/Users/leo.romanovsky/.sdkman/candidates/java/17.0.13-tem ./gradlew --no-daemon clean build -PDdSdkReactNative_minSdkVersion=24 from packages/core/android.
• xcodebuild -workspace example-new-architecture/ios/DdSdkReactNativeExample.xcworkspace -scheme DatadogSDKReactNative-Unit-Tests test -destination 'platform=iOS Simulator,id=DACA5ADA-1149-4987-9ED2-1F76A786B332' passes, 193 tests including the Swift shared-corpus evaluator test.
• ANDROID_HOME=/opt/homebrew/share/android-commandlinetools ANDROID_SDK_ROOT=/opt/homebrew/share/android-commandlinetools JAVA_HOME=/Users/leo.romanovsky/.sdkman/candidates/java/17.0.13-tem ./example-new-architecture/scripts/native-ffe-offline-android-smoke.sh passes and renders Native FFE offline fixture pass: 233 cases across 30 files.
• This same Android smoke is wired into test:native-android, so CI now exercises the offline corpus from React Native JS through the native Android bridge without credentials.

[datadog-official]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

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