feat: provider wrapper to support state race fix

Signed-off-by: Todd Baert <todd.baert@dynatrace.com>

Author: toddbaert

openfeature/event_executor.go

@@ -150,9 +150,16 @@ func (e *eventExecutor) GetClientRegistry(client string) scopedCallback {
 // emitOnRegistration fulfils the spec requirement to fire events if the
 // event type and the state of the associated provider are compatible.
 func (e *eventExecutor) emitOnRegistration(domain string, providerReference providerReference, eventType EventType, callback EventCallback) {
-	state, ok := e.loadState(domain)
-	if !ok {
-		return
+	var state State
+	// state-managing providers own their state; read directly
+	if smp, ok := providerReference.featureProvider.(StateManagingProvider); ok {
+		state = smp.State()
+	} else {
+		var ok bool
+		state, ok = e.loadState(domain)
+		if !ok {
+			return
+		}
 	}
 
 	var message string
@@ -185,6 +192,20 @@ func (e *eventExecutor) loadState(domain string) (State, bool) {
 }
 
 func (e *eventExecutor) State(domain string) State {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	// find the provider reference for this domain
+	ref, ok := e.namedProviderReference[domain]
+	if !ok {
+		ref = e.defaultProviderReference
+	}
+
+	// state-managing providers own their state; read directly
+	if smp, ok := ref.featureProvider.(StateManagingProvider); ok {
+		return smp.State()
+	}
+
 	state, _ := e.loadState(domain)
 	return state
 }
@@ -297,6 +318,8 @@ func (e *eventExecutor) triggerEvent(event Event, handler FeatureProvider) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
+	_, delegateManagesState := handler.(StateManagingProvider)
+
 	// first run API handlers
 	for _, c := range e.apiRegistry[event.EventType] {
 		e.executeHandler(*c, event)
@@ -308,7 +331,10 @@ func (e *eventExecutor) triggerEvent(event Event, handler FeatureProvider) {
 			continue
 		}
 
-		e.states.Store(domain, stateFromEvent(event))
+		// state-managing providers own their state; skip SDK-side writes
+		if !delegateManagesState {
+			e.states.Store(domain, stateFromEvent(event))
+		}
 		for _, c := range e.scopedRegistry[domain].callbacks[event.EventType] {
 			e.executeHandler(*c, event)
 		}
@@ -319,7 +345,10 @@ func (e *eventExecutor) triggerEvent(event Event, handler FeatureProvider) {
 	}
 
 	// handling the default provider
-	e.states.Store(defaultDomain, stateFromEvent(event))
+	// state-managing providers own their state; skip SDK-side writes
+	if !delegateManagesState {
+		e.states.Store(defaultDomain, stateFromEvent(event))
+	}
 	// invoke default provider bound (no provider associated) handlers by filtering
 	for domain, registry := range e.scopedRegistry {
 		if _, ok := e.namedProviderReference[domain]; ok {

openfeature/openfeature_api.go

@@ -117,10 +117,16 @@ func (api *evaluationAPI) setNamedProviderWithContext(ctx context.Context, clien
 func (api *evaluationAPI) initNew(ctx context.Context, clientName string, newProvider FeatureProvider) <-chan error {
 	errCh := make(chan error, 1)
 
+	_, delegateManagesState := newProvider.(StateManagingProvider)
+
 	// Initialize new provider async. The caller may wait on the channel.
 	go func(executor *eventExecutor, evalCtx EvaluationContext, ctx context.Context, provider FeatureProvider, clientName string) {
 		event, err := initializerWithContext(ctx, provider, evalCtx)
-		executor.triggerEvent(event, provider)
+
+		// State-managing providers emit their own events; skip SDK-side emission.
+		if !delegateManagesState {
+			executor.triggerEvent(event, provider)
+		}
 
 		if err != nil {
 			if clientName == "" {

openfeature/provider.go

@@ -105,6 +105,28 @@ func (s *NoopStateHandler) Shutdown() {
 	// NOOP
 }
 
+// StateManagingProvider is a provider that manages its own state. The SDK reads
+// state from the provider rather than maintaining shadow state. Implementations
+// MUST ensure that State() is safe for concurrent access and that state
+// transitions and associated event emissions are atomic from the perspective of
+// external observers.
+//
+// Legacy providers that do not implement this interface continue to have their
+// state managed by the SDK (deprecated behavior; to be removed in the next
+// major version).
+type StateManagingProvider interface {
+	FeatureProvider
+	StateHandler
+	EventHandler
+
+	// State returns the current provider state. Must reflect NotReadyState
+	// before Init is called and after Shutdown completes. Must reflect
+	// ReadyState if Init returns nil.
+	//
+	// This method must be safe for concurrent access.
+	State() State
+}
+
 // Eventing
 
 // EventHandler is the eventing contract enforced for FeatureProvider

openfeature/reference.go

@@ -6,10 +6,12 @@ import (
 
 // newProviderRef creates a new providerReference instance that wraps around a FeatureProvider implementation
 func newProviderRef(provider FeatureProvider) providerReference {
+	_, managesState := provider.(StateManagingProvider)
 	return providerReference{
-		featureProvider:   provider,
-		kind:              reflect.TypeOf(provider).Kind(),
-		shutdownSemaphore: make(chan any, 1),
+		featureProvider:      provider,
+		kind:                 reflect.TypeOf(provider).Kind(),
+		shutdownSemaphore:    make(chan any, 1),
+		delegateManagesState: managesState,
 	}
 }
 
@@ -19,6 +21,8 @@ type providerReference struct {
 	featureProvider   FeatureProvider
 	kind              reflect.Kind
 	shutdownSemaphore chan any
+	// delegateManagesState is true when the provider implements StateManagingProvider
+	delegateManagesState bool
 }
 
 func (pr providerReference) equals(other providerReference) bool {