docs: add comment to the override examples (#1058)

Author: zhiying-lin

examples/test-cro1.yaml

@@ -19,5 +19,9 @@ spec:
                   env: canary
         jsonPatchOverrides:
           - op: add
+            # Note: the override will fail if there are no labels on the resource.
+            # To add a new label to an empty map or overwrite the existing labels, please use /metadata/labels.
+            # Path: /metadata/labels
+            # value: {"new-label": "new-value"}
             path: /metadata/labels/new-label
-            value: "new-value"
+            value: "new-value"

examples/test-ro1.yaml

@@ -24,6 +24,9 @@ spec:
                   test-key: test-value2
         jsonPatchOverrides:
           - op: add
-            path: /metadata/labels
-            value:
-              new-label: new-value
+            # Note: the override will fail if there are no labels on the resource.
+            # To add a new label to an empty map or overwrite the existing labels, please use /metadata/labels.
+            # Path: /metadata/labels
+            # value: {"new-label": "new-value"}
+            path: /metadata/labels/new-label
+            value: "new-value"

pkg/controllers/workgenerator/override_test.go

@@ -2114,6 +2114,68 @@ func TestApplyJSONPatchOverride(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "reset the labels using add operation",
+			deployment: appsv1.Deployment{
+				TypeMeta: deploymentType,
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "deployment-name",
+					Namespace: "deployment-namespace",
+					Labels: map[string]string{
+						"app": "nginx-1",
+						"key": "value",
+					},
+				},
+			},
+			overrides: []placementv1alpha1.JSONPatchOverride{
+				{
+					Operator: placementv1alpha1.JSONPatchOverrideOpAdd,
+					Path:     "/metadata/labels",
+					Value:    apiextensionsv1.JSON{Raw: []byte(`{"app": "nginx"}`)},
+				},
+			},
+			wantDeployment: appsv1.Deployment{
+				TypeMeta: deploymentType,
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "deployment-name",
+					Namespace: "deployment-namespace",
+					Labels: map[string]string{
+						"app": "nginx",
+					},
+				},
+			},
+		},
+		{
+			name: "reset the labels using replace operation",
+			deployment: appsv1.Deployment{
+				TypeMeta: deploymentType,
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "deployment-name",
+					Namespace: "deployment-namespace",
+					Labels: map[string]string{
+						"app": "nginx-1",
+						"key": "value",
+					},
+				},
+			},
+			overrides: []placementv1alpha1.JSONPatchOverride{
+				{
+					Operator: placementv1alpha1.JSONPatchOverrideOpReplace,
+					Path:     "/metadata/labels",
+					Value:    apiextensionsv1.JSON{Raw: []byte(`{"app": "nginx"}`)},
+				},
+			},
+			wantDeployment: appsv1.Deployment{
+				TypeMeta: deploymentType,
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "deployment-name",
+					Namespace: "deployment-namespace",
+					Labels: map[string]string{
+						"app": "nginx",
+					},
+				},
+			},
+		},
 		{
 			name: "add the first label key value",
 			deployment: appsv1.Deployment{
@@ -2125,6 +2187,7 @@ func TestApplyJSONPatchOverride(t *testing.T) {
 			},
 			overrides: []placementv1alpha1.JSONPatchOverride{
 				{
+					// To add the first key, it cannot use "replace" as the path is missing.
 					Operator: placementv1alpha1.JSONPatchOverrideOpAdd,
 					Path:     "/metadata/labels",
 					Value:    apiextensionsv1.JSON{Raw: []byte(`{"app": "nginx"}`)},