For a non-single resource, if there is no update method, use create as update method (Azure#53456)

* For a non-single resource, if there is no update method, we should use create as update method

* refine

Author: live1206

eng/packages/http-client-csharp-mgmt/generator/Azure.Generator.Management/src/Providers/ResourceClientProvider.cs

@@ -414,11 +414,6 @@ protected override MethodProvider[] BuildMethods()
                 var methodKind = resourceMethod.Kind;
                 var method = resourceMethod.InputMethod;
                 var inputClient = resourceMethod.InputClient;
-                // exclude the List operations for resource and Create operations for non-singleton resources (they will be in ResourceCollection)
-                if (methodKind == ResourceOperationKind.List || (!IsSingleton && methodKind == ResourceOperationKind.Create))
-                {
-                    continue;
-                }
 
                 var isFakeLro = ResourceHelpers.ShouldMakeLro(methodKind);
 

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

@@ -48,6 +48,9 @@ public static ResourceMethodCategory CategorizeMethods(this ResourceMetadata res
             var methodsInResource = new List<ResourceMethod>();
             var methodsInCollection = new List<ResourceMethod>();
             var methodsInExtension = new List<ResourceMethod>();
+            bool hasUpdateMethod = false;
+            ResourceMethod? createMethod = null;
+
             foreach (var method in resourceMetadata.Methods)
             {
                 var isSingleton = resourceMetadata.SingletonResourceName is not null;
@@ -63,13 +66,17 @@ public static ResourceMethodCategory CategorizeMethods(this ResourceMetadata res
                         {
                             methodsInCollection.Add(method);
                         }
+                        createMethod = method;
                         break;
                     case ResourceOperationKind.Get:
                         // both resource and collection should have get method
                         methodsInResource.Add(method);
                         methodsInCollection.Add(method);
                         break;
                     case ResourceOperationKind.Update:
+                        hasUpdateMethod = true;
+                        methodsInResource.Add(method);
+                        break;
                     case ResourceOperationKind.Delete:
                         // only resource has get
                         methodsInResource.Add(method);
@@ -114,6 +121,12 @@ public static ResourceMethodCategory CategorizeMethods(this ResourceMetadata res
                 }
             }
 
+            // For non-singleton resource, if there is no update method, we will add the create method as update to the resource methods.
+            if (resourceMetadata.SingletonResourceName is null && !hasUpdateMethod && createMethod is not null)
+            {
+                methodsInResource.Add(createMethod);
+            }
+
             return new(methodsInResource, methodsInCollection, methodsInExtension);
         }
     }

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

@@ -51,8 +51,6 @@ interface Foos {
 
   delete is ArmResourceDeleteWithoutOkAsync<Foo>;
 
-  update is ArmCustomPatchAsync<Foo, Foo>;
-
   list is ArmResourceListByParent<Foo>;
 
   listBySubscription is ArmListBySubscription<Foo>;