fix: prevent double registration panic in fake client

- Check if GVK is already registered before adding to scheme
- Prevents panic when consuming applications pre-register types as typed structs
- Add test case for double registration scenario
- Fixes issue where fake client tries to register unstructured types for GVKs already registered as typed structs

Author: ecordell

client/fake/fake.go

@@ -714,8 +714,16 @@ func registerCRDTypesWithScheme(scheme *runtime.Scheme, crds []*apiextensionsv1.
 			}
 
 			// Register the types as unstructured for dynamic client compatibility
-			scheme.AddKnownTypeWithName(gvk, &unstructured.Unstructured{})
-			scheme.AddKnownTypeWithName(listGVK, &unstructured.UnstructuredList{})
+			// Check if the type is already registered to avoid conflicts with consuming
+			// applications that may have pre-registered the same GVK with typed structs.
+			// This prevents "Double registration of different types" panics when the same
+			// GVK is registered both as a typed struct and as unstructured.Unstructured.
+			if !scheme.Recognizes(gvk) {
+				scheme.AddKnownTypeWithName(gvk, &unstructured.Unstructured{})
+			}
+			if !scheme.Recognizes(listGVK) {
+				scheme.AddKnownTypeWithName(listGVK, &unstructured.UnstructuredList{})
+			}
 
 			// Add to GVR to ListKind mapping
 			gvr := schema.GroupVersionResource{

client/fake/fake_test.go

@@ -1734,3 +1734,109 @@ metadata:
 		require.NotNil(t, created)
 	})
 }
+
+func TestDoubleRegistrationWithTypedStruct(t *testing.T) {
+	// Create a test CRD
+	crd := &apiextensionsv1.CustomResourceDefinition{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "clusters.cockroach.cloud",
+		},
+		Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+			Group: "cockroach.cloud",
+			Names: apiextensionsv1.CustomResourceDefinitionNames{
+				Kind:     "Cluster",
+				Plural:   "clusters",
+				Singular: "cluster",
+			},
+			Scope: apiextensionsv1.NamespaceScoped,
+			Versions: []apiextensionsv1.CustomResourceDefinitionVersion{
+				{
+					Name:    "v1alpha1",
+					Served:  true,
+					Storage: true,
+					Schema: &apiextensionsv1.CustomResourceValidation{
+						OpenAPIV3Schema: &apiextensionsv1.JSONSchemaProps{
+							Type: "object",
+							Properties: map[string]apiextensionsv1.JSONSchemaProps{
+								"apiVersion": {Type: "string"},
+								"kind":       {Type: "string"},
+								"metadata":   {Type: "object"},
+								"spec": {
+									Type: "object",
+									Properties: map[string]apiextensionsv1.JSONSchemaProps{
+										"name": {Type: "string"},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+
+	// Create scheme
+	scheme := runtime.NewScheme()
+	if err := kscheme.AddToScheme(scheme); err != nil {
+		panic(err)
+	}
+
+	// Pre-register the same GVK that the CRD will try to register
+	// This simulates the case where a consuming application has already
+	// registered types in the scheme before creating the fake client
+	gvk := schema.GroupVersionKind{
+		Group:   "cockroach.cloud",
+		Version: "v1alpha1",
+		Kind:    "Cluster",
+	}
+	listGVK := schema.GroupVersionKind{
+		Group:   "cockroach.cloud",
+		Version: "v1alpha1",
+		Kind:    "ClusterList",
+	}
+
+	// Register as unstructured types first (simulating pre-registration)
+	scheme.AddKnownTypeWithName(gvk, &unstructured.Unstructured{})
+	scheme.AddKnownTypeWithName(listGVK, &unstructured.UnstructuredList{})
+
+	// This should NOT panic due to double registration
+	// Our fix should prevent the fake client from trying to register the same GVK
+	// again when it's already registered in the scheme
+	client := NewFakeDynamicClientWithCRDs(scheme, []*apiextensionsv1.CustomResourceDefinition{crd})
+
+	// Test that the client works correctly
+	clusterGVR := schema.GroupVersionResource{
+		Group:    "cockroach.cloud",
+		Version:  "v1alpha1",
+		Resource: "clusters",
+	}
+
+	cluster := &unstructured.Unstructured{
+		Object: map[string]interface{}{
+			"apiVersion": "cockroach.cloud/v1alpha1",
+			"kind":       "Cluster",
+			"metadata": map[string]interface{}{
+				"name":      "test-cluster",
+				"namespace": "default",
+			},
+			"spec": map[string]interface{}{
+				"name": "my-cluster",
+			},
+		},
+	}
+
+	// Test Create operation
+	created, err := client.Resource(clusterGVR).Namespace("default").Create(
+		t.Context(), cluster, metav1.CreateOptions{},
+	)
+	require.NoError(t, err)
+	require.NotNil(t, created)
+
+	// Test Get operation
+	retrieved, err := client.Resource(clusterGVR).Namespace("default").Get(
+		t.Context(), "test-cluster", metav1.GetOptions{},
+	)
+	require.NoError(t, err)
+	require.NotNil(t, retrieved)
+	require.Equal(t, "test-cluster", retrieved.GetName())
+}