chore: address review feedback

add integration test to wait for json without value
refactor JSON condition value parsing and validating
adjusting test to reflect the error message refactoring

staging/src/k8s.io/kubectl/pkg/cmd/wait/wait.go

@@ -250,15 +250,15 @@ func processJSONPathInput(jsonPathInput []string) (string, string, error) {
 	if err != nil {
 		return "", "", err
 	}
-	if len(jsonPathInput) > 1 {
+	if len(jsonPathInput) == 1 {
-		jsonPathValue := jsonPathInput[1]
-		if jsonPathValue == "" {
-			return "", "", errors.New("jsonpath wait value cannot be empty")
-		}
-		return relaxedJSONPathExp, strings.Trim(jsonPathValue, `'"`), nil
-	}
 		return relaxedJSONPathExp, "", nil
 	}
+	jsonPathValue := strings.Trim(jsonPathInput[1], `'"`)
+	if jsonPathValue == "" {
+		return "", "", errors.New("jsonpath wait has to have a value after equal sign, like --for=jsonpath='{.status.readyReplicas}'=3")
+	}
+	return relaxedJSONPathExp, jsonPathValue, nil
+}
 
 // ResourceLocation holds the location of a resource
 type ResourceLocation struct {

staging/src/k8s.io/kubectl/pkg/cmd/wait/wait_test.go

@@ -1556,13 +1556,13 @@ func TestWaitForJSONPathBadConditionParsing(t *testing.T) {
 		{
 			name:        "undefined value",
 			condition:   "jsonpath={.metadata.name}=",
-			expectedErr: "jsonpath wait value cannot be empty",
+			expectedErr: "jsonpath wait has to have a value after equal sign, like --for=jsonpath='{.status.readyReplicas}'=3",
 		},
 	}
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			_, err := conditionFuncFor(test.condition, io.Discard)
-			if err == nil {
+			if err == nil && test.expectedErr != "" {
 				t.Fatalf("expected %q, got empty", test.expectedErr)
 			}
 			if !strings.Contains(err.Error(), test.expectedErr) {

test/cmd/wait.sh

@@ -94,6 +94,21 @@ EOF
     # Clean deployment
     kubectl delete deployment dtest
 
+    # create test data
+    kubectl create deployment test-3 --image=busybox
+
+    # wait with jsonpath without value to succeed
+    set +o errexit
+    # Command: Wait with jsonpath without value
+    output_message=$(kubectl wait --for=jsonpath='{.status.replicas}' deploy/test-3 2>&1)
+    set -o errexit
+
+    # Post-Condition: Wait succeed
+    kube::test::if_has_string "${output_message}" 'deployment.apps/test-3 condition met'
+
+    # Clean deployment
+    kubectl delete deployment test-3
+
     set +o nounset
     set +o errexit
 }