check for items as well

Signed-off-by: Thiago Perrotta <thiago@perrotta.dev>

pkg/lint/rules/template.go

@@ -162,7 +162,7 @@ func TemplatesWithSkipSchemaValidation(linter *support.Linter, values map[string
 					// Refs https://github.com/helm/helm/issues/8596
 					// Skip metadata name validation for List resources as they don't require meaningful names
 					// Refs https://github.com/helm/helm/issues/13192
-					if !isListResource(yamlStruct) {
+					if !isListResource(yamlStruct, renderedContent) {
 						linter.RunLinterRule(support.WarningSev, fpath, validateMetadataName(yamlStruct))
 					}
 					linter.RunLinterRule(support.WarningSev, fpath, validateNoDeprecations(yamlStruct, kubeVersion))
@@ -240,9 +240,30 @@ func validateYamlContent(err error) error {
 }
 
 // isListResource returns true if the resource is a Kubernetes List type
-// (e.g. ConfigMapList, SecretList).
-func isListResource(obj *k8sYamlStruct) bool {
-	return strings.HasSuffix(obj.Kind, "List")
+// (e.g. ConfigMapList, SecretList). It checks both that the Kind ends with
+// "List" and that the resource has an "items" field that is an array.
+// This avoids incorrectly treating custom resources that happen to end with
+// "List" but aren't actually list containers.
+func isListResource(obj *k8sYamlStruct, manifest string) bool {
+	if !strings.HasSuffix(obj.Kind, "List") {
+		return false
+	}
+
+	// For the special case of Kind == "List", we can be sure it's a list
+	if obj.Kind == "List" {
+		return true
+	}
+
+	// For other kinds ending with "List", verify they have an items field
+	var listStruct struct {
+		Items []interface{} `json:"items"`
+	}
+	if err := yaml.Unmarshal([]byte(manifest), &listStruct); err != nil {
+		return false
+	}
+
+	// Check if the items field exists and is an array (even if empty)
+	return listStruct.Items != nil
 }
 
 // validateMetadataName uses the correct validation function for the object

pkg/lint/rules/template_test.go

@@ -442,21 +442,71 @@ items:
 func TestIsListResource(t *testing.T) {
 	tests := []struct {
 		kind     string
+		manifest string
 		expected bool
 	}{
-		{"ConfigMap", false},
-		{"ConfigMapList", true},
-		{"Secret", false},
-		{"SecretList", true},
-		{"List", true},
-		{"", false},
-		{"SomethingListExtra", false},
+		{"ConfigMap", `apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: test
+data:
+  key: value`, false},
+		{"ConfigMapList", `apiVersion: v1
+kind: ConfigMapList
+items:
+- apiVersion: v1
+  kind: ConfigMap
+  metadata:
+    name: test1
+- apiVersion: v1
+  kind: ConfigMap
+  metadata:
+    name: test2`, true},
+		{"Secret", `apiVersion: v1
+kind: Secret
+metadata:
+  name: test
+data:
+  key: value`, false},
+		{"SecretList", `apiVersion: v1
+kind: SecretList
+items:
+- apiVersion: v1
+  kind: Secret
+  metadata:
+    name: test1
+- apiVersion: v1
+  kind: Secret
+  metadata:
+    name: test2`, true},
+		{"List", `apiVersion: v1
+kind: List
+items:
+- apiVersion: v1
+  kind: ConfigMap
+  metadata:
+    name: test`, true},
+		{"", `apiVersion: v1
+kind: ""
+metadata:
+  name: test`, false},
+		{"SomethingListExtra", `apiVersion: v1
+kind: SomethingListExtra
+metadata:
+  name: test`, false},
+		// Test case for a custom resource ending in "List" but without items field (should be false)
+		{"AccessList", `apiVersion: example.com/v1
+kind: AccessList
+metadata:
+  name: test
+spec:
+  rules: []`, false},
 	}
 
 	for _, test := range tests {
 		t.Run(test.kind, func(t *testing.T) {
 			obj := &k8sYamlStruct{Kind: test.kind}
-			result := isListResource(obj)
+			result := isListResource(obj, test.manifest)
 			if result != test.expected {
 				t.Errorf("isListResource(%q) = %v, expected %v", test.kind, result, test.expected)
 			}