Fix unexpected additional parameter validation in model factory (#53465)

* Initial plan

* Fix ArgumentNullException in model factory methods

Remove incorrect ArgumentNullException XML documentation from model factory methods.
Model factory methods are designed for mocking and should allow all parameters to be null.
The implementation handles null parameters gracefully using ternary operators.

Co-authored-by: live1206 <[email protected]>

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

Co-authored-by: Copilot <[email protected]>

* Use Array.Empty instead of Enumerable.Empty to fix build issue

Co-authored-by: live1206 <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: live1206 <[email protected]>
Co-authored-by: Wei Hu <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: 3 people

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

@@ -3,7 +3,10 @@
 
 using Microsoft.TypeSpec.Generator.ClientModel;
 using Microsoft.TypeSpec.Generator.Providers;
+using Microsoft.TypeSpec.Generator.Statements;
+using System;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Azure.Generator.Management.Visitors
 {
@@ -19,6 +22,9 @@ internal class ModelFactoryVisitor : ScmLibraryVisitor
                     var returnType = method.Signature.ReturnType;
                     if (returnType is not null && ManagementClientGenerator.Instance.OutputLibrary.IsModelFactoryModelType(returnType))
                     {
+                        // Fix ArgumentNullException XML documentation for parameters that are nullable
+                        // Model factory methods should allow all parameters to be null for mocking purposes
+                        FixArgumentNullExceptionXmlDoc(method);
                         updatedMethods.Add(method);
                     }
                 }
@@ -27,5 +33,17 @@ internal class ModelFactoryVisitor : ScmLibraryVisitor
             }
             return base.VisitType(type);
         }
+
+        private void FixArgumentNullExceptionXmlDoc(MethodProvider method)
+        {
+            // Model factory methods are for mocking and should not have ArgumentNullException validation
+            // The method implementation uses ternary operators to handle null values gracefully
+            // Remove any ArgumentNullException documentation by clearing the exceptions list
+            if (method.XmlDocs != null)
+            {
+                // Clear exceptions to remove ArgumentNullException documentation
+                method.XmlDocs.Update(exceptions: Array.Empty<XmlDocExceptionStatement>());
+            }
+        }
     }
 }