config: Add handler field to configuration

Using the field we can avoid changing the actual logging during testing
by assigning a different function to the field.

We can now also verify that the handler field is being executed.

pkg/cvo/configuration/configuration.go

@@ -43,6 +43,14 @@ type ClusterVersionOperatorConfiguration struct {
 	started bool
 
 	configuration configuration
+
+	// Function to handle an update to the internal configuration.
+	//
+	// In the future, the desired configuration may be consumed via other controllers.
+	// This will require some sort of synchronization upon a configuration change.
+	// For the moment, the log level is the sole consumer of the configuration.
+	// Apply the log level directly here for simplicity for the time being.
+	handler func(configuration) error
 }
 
 func (config *ClusterVersionOperatorConfiguration) Queue() workqueue.TypedRateLimitingInterface[any] {
@@ -87,6 +95,7 @@ func NewClusterVersionOperatorConfiguration(client operatorclientset.Interface,
 		client:        client.OperatorV1alpha1().ClusterVersionOperators(),
 		factory:       factory,
 		configuration: configuration{desiredLogLevel: desiredLogLevel},
+		handler:       func(c configuration) error { return applyLogLevel(c.desiredLogLevel) },
 	}
 }
 
@@ -152,5 +161,8 @@ func (config *ClusterVersionOperatorConfiguration) sync(ctx context.Context, des
 		config.configuration.desiredLogLevel = operatorv1.Normal
 	}
 
-	return applyLogLevel(config.configuration.desiredLogLevel)
+	if config.handler != nil {
+		return config.handler(config.configuration)
+	}
+	return nil
 }

pkg/cvo/configuration/configuration_test.go

@@ -24,6 +24,7 @@ func TestClusterVersionOperatorConfiguration_sync(t *testing.T) {
 		expectedConfig         operatorv1alpha1.ClusterVersionOperator
 		internalConfig         configuration
 		expectedInternalConfig configuration
+		handlerFunctionCalled  bool
 	}{
 		{
 			name: "first sync run correctly updates the status",
@@ -54,6 +55,7 @@ func TestClusterVersionOperatorConfiguration_sync(t *testing.T) {
 				desiredLogLevel:        operatorv1.Normal,
 				lastObservedGeneration: 1,
 			},
+			handlerFunctionCalled: true,
 		},
 		{
 			name: "sync updates observed generation correctly",
@@ -87,6 +89,7 @@ func TestClusterVersionOperatorConfiguration_sync(t *testing.T) {
 				desiredLogLevel:        operatorv1.Normal,
 				lastObservedGeneration: 3,
 			},
+			handlerFunctionCalled: true,
 		},
 		{
 			name: "sync updates desired log level correctly",
@@ -120,6 +123,7 @@ func TestClusterVersionOperatorConfiguration_sync(t *testing.T) {
 				desiredLogLevel:        operatorv1.Trace,
 				lastObservedGeneration: 4,
 			},
+			handlerFunctionCalled: true,
 		},
 		{
 			name: "number of not observed generations does not impact sync",
@@ -153,6 +157,7 @@ func TestClusterVersionOperatorConfiguration_sync(t *testing.T) {
 				desiredLogLevel:        operatorv1.TraceAll,
 				lastObservedGeneration: 40,
 			},
+			handlerFunctionCalled: true,
 		},
 	}
 	for _, tt := range tests {
@@ -166,6 +171,12 @@ func TestClusterVersionOperatorConfiguration_sync(t *testing.T) {
 
 			configController := NewClusterVersionOperatorConfiguration(client, factory)
 
+			called := false
+			configController.handler = func(_ configuration) error {
+				called = true
+				return nil
+			}
+
 			ctx, cancelFunc := context.WithDeadline(context.Background(), time.Now().Add(time.Minute))
 
 			if err := configController.Start(ctx); err != nil {
@@ -194,6 +205,10 @@ func TestClusterVersionOperatorConfiguration_sync(t *testing.T) {
 				t.Errorf("unexpected config (-want, +got) = %v", diff)
 			}
 
+			if tt.handlerFunctionCalled != called {
+				t.Errorf("unexpected handler function execution; wanted=%v, got=%v", tt.handlerFunctionCalled, called)
+			}
+
 			// Shutdown created resources
 			cancelFunc()
 		})