fix: Handle closed EventChannel from multiprovider (#461)

Signed-off-by: Saleem Rashid <dev@saleemrashid.com>

Author: saleemrashid

openfeature/event_executor.go

@@ -222,25 +222,25 @@ func (e *eventExecutor) startListeningAndShutdownOld(newProvider providerReferen
 	if !isRunning(newProvider, e.activeSubscriptions) {
 		e.activeSubscriptions = append(e.activeSubscriptions, newProvider)
 
-		go func() {
-			v, ok := newProvider.featureProvider.(EventHandler)
-			if !ok {
-				return
-			}
-
-			// event handling of the new feature provider
-			for {
-				select {
-				case event := <-v.EventChannel():
-					e.eventChan <- eventPayload{
-						event:   event,
-						handler: newProvider.featureProvider,
+		if v, ok := newProvider.featureProvider.(EventHandler); ok {
+			go func() {
+				// event handling of the new feature provider
+				for {
+					select {
+					case event, ok := <-v.EventChannel():
+						if !ok {
+							return
+						}
+						e.eventChan <- eventPayload{
+							event:   event,
+							handler: newProvider.featureProvider,
+						}
+					case <-newProvider.shutdownSemaphore:
+						return
 					}
-				case <-newProvider.shutdownSemaphore:
-					return
 				}
-			}
-		}()
+			}()
+		}
 	}
 
 	// shutdown old provider handling

openfeature/event_executor_test.go

@@ -4,8 +4,11 @@ import (
 	"errors"
 	"reflect"
 	"slices"
+	"sync/atomic"
 	"testing"
 	"time"
+
+	"github.com/stretchr/testify/require"
 )
 
 func init() {
@@ -1541,3 +1544,44 @@ func TestEventHandler_APIRemoval(t *testing.T) {
 		executor.RemoveClientHandler("a", ProviderReady, &h1)
 	})
 }
+
+func TestEventHandler_ChannelClosure(t *testing.T) {
+	eventingImpl := &ProviderEventing{
+		c: make(chan Event, 1),
+	}
+
+	eventingProvider := struct {
+		FeatureProvider
+		EventHandler
+	}{
+		NoopProvider{},
+		eventingImpl,
+	}
+
+	executor := newEventExecutor()
+
+	err := executor.registerDefaultProvider(eventingProvider)
+	require.NoError(t, err)
+	require.Len(t, executor.activeSubscriptions, 1)
+
+	var eventCount atomic.Int64
+	callBack := func(e EventDetails) {
+		eventCount.Add(1)
+	}
+	executor.AddHandler(ProviderReady, &callBack)
+	// watch for empty events
+	executor.AddHandler("", &callBack)
+	eventingImpl.Invoke(Event{EventType: ProviderReady})
+
+	require.Eventually(t, func() bool {
+		return eventCount.Load() >= 1
+	}, 100*time.Millisecond, 10*time.Millisecond, "event not received")
+
+	initialCount := eventCount.Load()
+	eventingImpl.Close()
+
+	<-time.After(100 * time.Millisecond)
+
+	afterCount := eventCount.Load()
+	require.Equal(t, initialCount, afterCount, "goroutine processed events after channel closed - indicates channel closure not detected")
+}

openfeature/util_test.go

@@ -65,6 +65,10 @@ func (s ProviderEventing) EventChannel() <-chan Event {
 	return s.c
 }
 
+func (s ProviderEventing) Close() {
+	close(s.c)
+}
+
 func eventually(t *testing.T, condition func() bool, timeout, interval time.Duration, errMsg string) {
 	t.Helper()