bug: Fix APIServerLB nil pointer deref

This commit fixes a possible nil pointer deference when returning the
name of the API Server LoadBalancer. In some cases like externally
managed infrastructure, there might not be an API Server LoadBalancer in
 the AzureCluster CR.

Signed-off-by: Bryan Cox <[email protected]>

Author: bryan-cox

azure/scope/cluster.go

@@ -769,7 +769,11 @@ func (s *ClusterScope) ControlPlaneOutboundLB() *infrav1.LoadBalancerSpec {
 
 // APIServerLBName returns the API Server LB name.
 func (s *ClusterScope) APIServerLBName() string {
-	return s.APIServerLB().Name
+	apiServerLB := s.APIServerLB()
+	if apiServerLB != nil {
+		return apiServerLB.Name
+	}
+	return ""
 }
 
 // IsAPIServerPrivate returns true if the API Server LB is of type Internal.

azure/scope/cluster_test.go

@@ -3973,3 +3973,46 @@ func TestGroupSpecs(t *testing.T) {
 		})
 	}
 }
+
+func TestAPIServerLBName(t *testing.T) {
+	tests := []struct {
+		name     string
+		cluster  *ClusterScope
+		expected string
+	}{
+		{
+			name: "APIServerLB is not nil",
+			cluster: &ClusterScope{
+				AzureCluster: &infrav1.AzureCluster{
+					Spec: infrav1.AzureClusterSpec{
+						NetworkSpec: infrav1.NetworkSpec{
+							APIServerLB: &infrav1.LoadBalancerSpec{
+								Name: "test-lb",
+							},
+						},
+					},
+				},
+			},
+			expected: "test-lb",
+		},
+		{
+			name: "APIServerLB is nil",
+			cluster: &ClusterScope{
+				AzureCluster: &infrav1.AzureCluster{
+					Spec: infrav1.AzureClusterSpec{
+						NetworkSpec: infrav1.NetworkSpec{},
+					},
+				},
+			},
+			expected: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			g := NewWithT(t)
+			result := tt.cluster.APIServerLBName()
+			g.Expect(result).To(Equal(tt.expected))
+		})
+	}
+}