Fix missing constructor parameters in model factory nested UpdateProperties generation

eng/packages/http-client-csharp-mgmt/generator/Azure.Generator.Management/src/Visitors/FlattenPropertyVisitor.cs

@@ -306,11 +306,28 @@ private ValueExpression[] BuildConstructorParameters(CSharpType propertyType, Li
                                     var innerParameters = BuildConstructorParameters(constructorParameterType, innerFlattenedProperties, parameterMap);
                                     parameters.Add(New.Instance(constructorParameterType, innerParameters));
                                 }
-                                // Note: If innerFlattenedProperties is empty, we skip adding this parameter.
-                                // This can happen when the nested model has no required properties, and all
-                                // flattened properties are optional. In such cases, the model factory will
-                                // not include this nested object in the constructor call.
+                                else
+                                {
+                                    // If innerFlattenedProperties is empty, we still need to add a parameter
+                                    // to maintain the correct parameter count for the constructor.
+                                    // This can happen when the nested model has no required properties, and all
+                                    // flattened properties are optional.
+                                    // Use Default.CastTo to handle both value types and reference types correctly.
+                                    parameters.Add(Default.CastTo(constructorParameterType));
+                                }
                             }
+                            else
+                            {
+                                // Constructor parameter not found in propertyNameMap, add default as parameter
+                                // Use Default.CastTo to handle both value types and reference types correctly.
+                                parameters.Add(Default.CastTo(constructorParameterType));
+                            }
+                        }
+                        else
+                        {
+                            // propertyType not found in _flattenedModelTypes, add default as parameter
+                            // Use Default.CastTo to handle both value types and reference types correctly.
+                            parameters.Add(Default.CastTo(constructorParameterType));
                         }
                     }
                 }

eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/main.tsp

@@ -21,6 +21,7 @@ import "./resourcedata.tsp";
 import "./scheduledaction.tsp";
 import "./vmgroup.tsp";
 import "./chaos.tsp";
+import "./redisenterprise.tsp";
 import "./propertyoverride.tsp";
 import "./sitemanager.tsp";
 import "./flatten-with-customized-property.tsp";

eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/redisenterprise.tsp

@@ -0,0 +1,247 @@
+import "@typespec/http";
+import "@typespec/rest";
+import "@azure-tools/typespec-azure-core";
+import "@azure-tools/typespec-azure-resource-manager";
+import "@azure-tools/typespec-client-generator-core";
+
+using TypeSpec.Http;
+using TypeSpec.Rest;
+using Azure.Core;
+using Azure.ResourceManager;
+using Azure.ClientGenerator.Core;
+
+namespace MgmtTypeSpec {
+
+  @armResourceOperations
+  interface Clusters {
+    get is ArmResourceRead<Cluster>;
+    createOrUpdate is ArmResourceCreateOrReplaceAsync<Cluster>;
+    update is ArmResourcePatchAsync<Cluster, ClusterUpdate>;
+    delete is ArmResourceDeleteAsync<Cluster>;
+    listByResourceGroup is ArmResourceListByParent<Cluster>;
+    listBySubscription is ArmListBySubscription<Cluster>;
+  }
+
+  model Cluster is TrackedResource<ClusterProperties> {
+    ...ResourceNameParameter<Cluster>;
+  }
+
+  /**
+   * Patch model that has properties flattened - this is the key pattern from
+   * the original issue where the factory method was missing constructor parameters.
+   */
+  model ClusterUpdate {
+    /**
+     * The SKU to create, which affects price, performance, and features.
+     */
+    sku?: Sku;
+
+    /**
+     * Other properties of the cluster - this gets flattened via decorator.
+     */
+    properties?: ClusterUpdateProperties;
+
+    /**
+     * The identity of the resource.
+     */
+    identity?: ManagedServiceIdentityProperty;
+
+    /**
+     * Resource tags.
+     */
+    @visibility(Lifecycle.Read, Lifecycle.Create, Lifecycle.Update)
+    tags?: Record<string>;
+  }
+
+  /**
+   * Extended properties model - extends ClusterProperties which has nested
+   * complex objects (encryption, maintenanceConfiguration). The original issue
+   * was that the factory method for ClusterUpdate was calling
+   * new ClusterUpdateProperties(...) with missing parameters for these nested objects.
+   */
+  model ClusterUpdateProperties extends ClusterProperties {
+    /**
+     * Whether or not public network traffic can access the Redis cluster.
+     */
+    publicNetworkAccess?: PublicNetworkAccess | null;
+  }
+
+  model ClusterProperties {
+    /**
+     * Enabled by default. If highAvailability is disabled, the data set is not replicated.
+     */
+    highAvailability?: HighAvailability;
+
+    /**
+     * The minimum TLS version for the cluster to support, e.g. '1.2'.
+     */
+    minimumTlsVersion?: TlsVersion;
+
+    /**
+     * Encryption-at-rest configuration for the cluster.
+     * This nested object was missing in the factory constructor call.
+     */
+    encryption?: ClusterPropertiesEncryption;
+
+    /**
+     * Cluster-level maintenance configuration.
+     * This nested object was missing in the factory constructor call.
+     */
+    @visibility(Lifecycle.Read, Lifecycle.Create, Lifecycle.Update)
+    maintenanceConfiguration?: MaintenanceConfiguration;
+
+    /**
+     * DNS name of the cluster endpoint
+     */
+    @visibility(Lifecycle.Read)
+    hostName?: string;
+
+    /**
+     * Current provisioning status of the cluster
+     */
+    @visibility(Lifecycle.Read)
+    provisioningState?: ProvisioningState;
+
+    /**
+     * Explains the current redundancy strategy of the cluster.
+     */
+    @visibility(Lifecycle.Read)
+    redundancyMode?: RedundancyMode;
+
+    /**
+     * Current resource status of the cluster
+     */
+    @visibility(Lifecycle.Read)
+    resourceState?: ResourceState;
+
+    /**
+     * Version of redis the cluster supports, e.g. '6'
+     */
+    @visibility(Lifecycle.Read)
+    redisVersion?: string;
+
+    /**
+     * List of private endpoint connections
+     */
+    @visibility(Lifecycle.Read)
+    privateEndpointConnections?: RedisPrivateEndpointConnection[];
+  }
+
+  model Sku {
+    name: SkuName;
+    capacity?: int32;
+  }
+
+  model ClusterPropertiesEncryption {
+    customerManagedKeyEncryption?: CustomerManagedKeyEncryption;
+  }
+
+  model CustomerManagedKeyEncryption {
+    keyEncryptionKeyIdentity?: KeyEncryptionKeyIdentity;
+    keyEncryptionKeyUrl?: string;
+  }
+
+  model KeyEncryptionKeyIdentity {
+    userAssignedIdentityResourceId?: string;
+    identityType?: CmkIdentityType;
+  }
+
+  model MaintenanceConfiguration {
+    maintenanceWindows?: MaintenanceWindow[];
+  }
+
+  model MaintenanceWindow {
+    dayOfWeek?: DayOfWeek;
+    startHour?: int32;
+    duration?: int32;
+  }
+
+  enum SkuName {
+    Standard,
+    Premium,
+  }
+
+  enum HighAvailability {
+    Enabled,
+    Disabled,
+  }
+
+  enum TlsVersion {
+    "1.0",
+    "1.1",
+    "1.2",
+  }
+
+  enum PublicNetworkAccess {
+    Enabled,
+    Disabled,
+  }
+
+  enum ProvisioningState {
+    Succeeded,
+    Failed,
+    Canceled,
+    Creating,
+    Updating,
+    Deleting,
+  }
+
+  enum RedundancyMode {
+    Disabled,
+    GeoReplicated,
+    ZoneReplicated,
+  }
+
+  enum ResourceState {
+    Running,
+    Creating,
+    Updating,
+    Deleting,
+    Disabled,
+  }
+
+  enum CmkIdentityType {
+    SystemAssignedIdentity,
+    UserAssignedIdentity,
+  }
+
+  enum DayOfWeek {
+    Monday,
+    Tuesday,
+    Wednesday,
+    Thursday,
+    Friday,
+    Saturday,
+    Sunday,
+  }
+
+  model RedisPrivateEndpointConnection is ProxyResource<RedisPrivateEndpointConnectionProperties> {
+    ...ResourceNameParameter<RedisPrivateEndpointConnection>;
+  }
+
+  model RedisPrivateEndpointConnectionProperties {
+    privateEndpoint?: RedisPrivateEndpoint;
+    privateLinkServiceConnectionState: RedisPrivateLinkServiceConnectionState;
+    provisioningState?: ProvisioningState;
+  }
+
+  model RedisPrivateEndpoint {
+    id?: string;
+  }
+
+  model RedisPrivateLinkServiceConnectionState {
+    status?: RedisPrivateEndpointServiceConnectionStatus;
+    description?: string;
+    actionsRequired?: string;
+  }
+
+  enum RedisPrivateEndpointServiceConnectionStatus {
+    Pending,
+    Approved,
+    Rejected,
+  }
+
+  // Apply property flattening to ClusterUpdate.properties - this triggers the bug
+  #suppress "deprecated"
+  @@Azure.ClientGenerator.Core.Legacy.flattenProperty(ClusterUpdate.properties);
+}