Remove setter for safeflatten collection-type property and handle nullability check (Azure#52574)

* Remove setter for safeflatten collection-type property and handle nullability check

* cleanup

* cleanup

Author: live1206

eng/packages/http-client-csharp-mgmt/generator/Azure.Generator.Management/src/Utilities/PropertyHelpers.cs

@@ -84,7 +84,7 @@ public static MethodBodyStatement BuildGetter(bool? includeGetterNullCheck, Prop
         {
             var checkNullExpression = This.Property(internalProperty.Name).Is(Null);
             // For collection types, we do not do null check and initialization in getter, they have been initialized in constructor.
-            if (innerProperty.Type.IsCollection)
+            if (innerProperty.Type.IsCollection && internalProperty.WireInfo?.IsRequired == true)
             {
                 return new List<MethodBodyStatement>() { Return(new MemberExpression(internalProperty, innerProperty.Name)) };
             }
@@ -113,8 +113,13 @@ public static MethodBodyStatement BuildGetter(bool? includeGetterNullCheck, Prop
             }
         }
 
-        public static MethodBodyStatement BuildSetterForPropertyFlatten(ModelProvider innerModel, PropertyProvider internalProperty, PropertyProvider innerProperty)
+        public static MethodBodyStatement? BuildSetterForPropertyFlatten(ModelProvider innerModel, PropertyProvider internalProperty, PropertyProvider innerProperty)
         {
+            if (innerProperty.Type.IsCollection)
+            {
+                return null;
+            }
+
             var isNullableValueType = innerProperty.Type.IsValueType && innerProperty.Type.IsNullable;
             var setter = new List<MethodBodyStatement>();
             var internalPropertyExpression = This.Property(internalProperty.Name);
@@ -128,8 +133,13 @@ public static MethodBodyStatement BuildSetterForPropertyFlatten(ModelProvider in
             return setter;
         }
 
-        public static MethodBodyStatement BuildSetterForSafeFlatten(bool includeSetterCheck, ModelProvider innerModel, PropertyProvider internalProperty, PropertyProvider innerProperty)
+        public static MethodBodyStatement? BuildSetterForSafeFlatten(bool includeSetterCheck, ModelProvider innerModel, PropertyProvider internalProperty, PropertyProvider innerProperty)
         {
+            if (innerProperty.Type.IsCollection)
+            {
+                return null;
+            }
+
             var isOverriddenValueType = IsOverriddenValueType(innerProperty);
             var setter = new List<MethodBodyStatement>();
             var internalPropertyExpression = This.Property(internalProperty.Name);

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

@@ -301,7 +301,7 @@ private void FlattenProperties(ModelProvider model)
                             var (_, includeGetterNullCheck, _) = PropertyHelpers.GetFlags(property, innerProperty);
                             var flattenPropertyName = innerProperty.Name; // TODO: handle name conflicts
                             var flattenPropertyBody = new MethodPropertyBody(
-                                PropertyHelpers.BuildGetter(includeGetterNullCheck == true && !innerProperty.Type.IsCollection, property, modelProvider, innerProperty),
+                                PropertyHelpers.BuildGetter(includeGetterNullCheck, property, modelProvider, innerProperty),
                                 !innerProperty.Body.HasSetter ? null : PropertyHelpers.BuildSetterForPropertyFlatten(modelProvider, property, innerProperty)
                             );
 

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

@@ -51,6 +51,7 @@ model BarSettingsResource is ProxyResource<BarSettingsProperties> {
   property: BarQuotaProperties;
   anotherProperty: BarQuotaProperties;
   flattenedNestedProperty: BarNestedQuotaProperties;
+  optionalFlattenProperty?: optionalFlattenPropertyType;
 }
 
 @parentResource(Bar)
@@ -68,6 +69,10 @@ model BarMiddleNestedQuotaProperties extends BarDeeplyNestedQuotaProperties {
   middleProp2: Record<string>;
 }
 
+model optionalFlattenPropertyType {
+  randomCollectionProp: string[];
+}
+
 model BarDeeplyNestedQuotaProperties {
   innerProp1?: int32;
   innerProp2: string;