Remove logic that moves models out of models directory once migration is complete (#54132)

* Initial plan

* Remove logic that moves models out of models directory

This removes the migration-specific logic that was added to the
NamespaceVisitor to move model files out of the Models directory
when model-namespace was set to false. This logic was originally
added to make GitHub diffs easier to review during the migration
to the new generator. Since diffs are now easy to understand,
this logic is no longer needed.

Fixes #50286

Co-authored-by: JoshLove-msft <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: JoshLove-msft <[email protected]>

Author: Copilot

eng/packages/http-client-csharp/generator/Azure.Generator/src/Visitors/NamespaceVisitor.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
-using System.IO;
 using Azure.Generator.Extensions;
 using Microsoft.TypeSpec.Generator;
 using Microsoft.TypeSpec.Generator.ClientModel;
@@ -72,20 +71,6 @@ private static void UpdateModelsNamespace(TypeProvider type)
                             $"{CodeModelGenerator.Instance.TypeFactory.PrimaryNamespace}.Models"));
                 }
             }
-            else
-            {
-                // TODO - remove this once all libraries have been migrated to the new generator. Leaving this
-                // here to make diffs easier to review while migrating. Calculate the fileName as it won't always match the Name
-                // property, e.g. for serialization providers.
-                // https://github.com/Azure/azure-sdk-for-net/issues/50286
-                var separator = Path.DirectorySeparatorChar;
-                if (type.RelativeFilePath.Contains($"Generated{separator}Models{separator}"))
-                {
-                    var fileName = Path.GetRelativePath(Path.Combine("src", "Generated", "Models"),
-                        type.RelativeFilePath);
-                    type.Update(relativeFilePath: Path.Combine("src", "Generated", fileName));
-                }
-            }
         }
     }
 }

eng/packages/http-client-csharp/generator/Azure.Generator/test/Visitors/NamespaceVisitorTests.cs

@@ -1,8 +1,6 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
-using System;
-using System.IO;
 using Microsoft.TypeSpec.Generator.Input;
 using Microsoft.TypeSpec.Generator.Providers;
 using NUnit.Framework;
@@ -41,38 +39,6 @@ public void DoesNotUseModelsNamespaceIfConfigSetToFalse()
             Assert.AreEqual("Samples", updatedModel!.Type.Namespace);
         }
 
-        [Test]
-        public void MovesModelsOutOfModelsDirectory()
-        {
-            MockHelpers.LoadMockGenerator(configurationJson: "{ \"package-name\": \"TestLibrary\", \"model-namespace\": false }");
-            var visitor = new TestNamespaceVisitor();
-            var inputType = InputFactory.Model("TestModel", "Samples");
-            var model = new ModelProvider(inputType);
-            var updatedModel = visitor.InvokePreVisitModel(inputType, model);
-
-            Assert.IsNotNull(updatedModel);
-            Assert.AreEqual(
-                $"src{Path.DirectorySeparatorChar}Generated{Path.DirectorySeparatorChar}{updatedModel!.Name}.cs",
-                updatedModel.RelativeFilePath);
-        }
-
-        [Test]
-        public void DoesNotMoveModelIfNotInModelsDirectory()
-        {
-            MockHelpers.LoadMockGenerator(configurationJson: "{ \"package-name\": \"TestLibrary\", \"model-namespace\": false }");
-            var visitor = new TestNamespaceVisitor();
-            var inputType = InputFactory.Model("TestModels", "Samples");
-            var model = new ModelProvider(inputType);
-
-            model.Update(relativeFilePath: $"src{Path.DirectorySeparatorChar}Generated{Path.DirectorySeparatorChar}{model.Name}.cs");
-            var updatedModel = visitor.InvokePreVisitModel(inputType, model);
-
-            Assert.IsNotNull(updatedModel);
-            Assert.AreEqual(
-                $"src{Path.DirectorySeparatorChar}Generated{Path.DirectorySeparatorChar}{updatedModel!.Name}.cs",
-                updatedModel.RelativeFilePath);
-        }
-
         [Test]
         public void DoesNotChangeNamespaceOfFormatEnum()
         {