fix: implement requirement 1.6.2 (#400)

fix: only shut down active providers

The spec says that shutdown must shut down active providers,
but the current logic shuts down inactive providers.

This change fixes that. Separately, the spec might also need to be modified
to say "only" active providers.

Signed-off-by: Brandon Duffany <[email protected]>

Author: bduffany

openfeature/openfeature.go

@@ -88,7 +88,10 @@ func RemoveHandler(eventType EventType, callback EventCallback) {
 	api.RemoveHandler(eventType, callback)
 }
 
-// Shutdown active providers
+// Shutdown unconditionally calls shutdown on all registered providers,
+// regardless of their state. It resets the state of the API, removing all
+// hooks, event handlers, and providers.
 func Shutdown() {
 	api.Shutdown()
+	initSingleton()
 }

openfeature/openfeature_test.go

@@ -585,6 +585,59 @@ func TestRequirement_1_6_1(t *testing.T) {
 	}
 }
 
+// The API's `shutdown` function MUST reset all state of the API, removing all
+// hooks, event handlers, and providers.
+func TestRequirement_1_6_2(t *testing.T) {
+	t.Cleanup(initSingleton)
+
+	// TODO: test that hooks and event handlers are removed as well. This only
+	// tests that providers are removed.
+
+	provider1, _, shutdownSem1 := setupProviderWithSemaphores()
+
+	// Setup provider and wait for initialization done
+	err := SetProviderAndWait(provider1)
+	if err != nil {
+		t.Errorf("error setting up provider %v", err)
+	}
+
+	Shutdown()
+
+	// Shutdown should be synchronous. Try a non-blocking receive and fail
+	// immediately if there is not a value in the channel.
+	select {
+	case <-shutdownSem1:
+		break
+	default:
+		t.Fatalf("shutdown not invoked")
+	}
+
+	// Try shutting down again, and make sure that provider1 is not shut down
+	// again, since it is now inactive.
+	provider2, _, shutdownSem2 := setupProviderWithSemaphores()
+
+	err = SetProviderAndWait(provider2)
+	if err != nil {
+		t.Errorf("error setting up provider %v", err)
+	}
+
+	Shutdown()
+
+	select {
+	case <-shutdownSem2:
+		break
+	default:
+		t.Fatalf("shutdown not invoked")
+	}
+
+	select {
+	case <-shutdownSem1:
+		t.Fatalf("provider1 should not have been shut down again, since it is unregistered")
+	case <-time.After(100 * time.Millisecond):
+		break
+	}
+}
+
 func TestRequirement_EventCompliance(t *testing.T) {
 	// The client MUST provide a function for associating handler functions with a particular provider event type.
 	// The API and client MUST provide a function allowing the removal of event handlers.