From d0c258efc02f5eaa4e34848dc8563eb217b2c034 Mon Sep 17 00:00:00 2001
From: Wei Hu <live1206@gmail.com>
Date: Thu, 7 Nov 2024 11:12:16 +0800
Subject: [PATCH] Update rest client and serialization generation for Azure
 plugin  (#46835)

---
 eng/Packages.Data.props                       |   2 +-
 .../Abstraction/HttpMessageProvider.cs        |  12 +-
 .../Abstraction/HttpPipelineProvider.cs       |  14 +-
 .../Abstraction/HttpRequestProvider.cs        |  79 +++++++++-
 .../BasicTypeSpecClient.RestClient.cs         | 149 ++++++++----------
 .../Generated/BasicTypeSpecModelFactory.cs    |  12 +-
 .../Internal/ClientPipelineExtensions.cs      |  16 +-
 .../Generated/Models/Friend.Serialization.cs  |   4 +
 ...equiredNullableProperties.Serialization.cs |   4 +
 .../Models/ProjectedModel.Serialization.cs    |   4 +
 ...rnsAnonymousModelResponse.Serialization.cs |   4 +
 .../Models/RoundTripModel.Serialization.cs    |  12 +-
 .../Generated/Models/Thing.Serialization.cs   |   8 +-
 eng/scripts/typespec/Generate-Code.ps1        |   4 +
 14 files changed, 194 insertions(+), 130 deletions(-)

diff --git a/eng/Packages.Data.props b/eng/Packages.Data.props
index 7ce470988218..1d290bfe1109 100644
--- a/eng/Packages.Data.props
+++ b/eng/Packages.Data.props
@@ -252,7 +252,7 @@
   </ItemGroup>
 
   <ItemGroup Condition="'$(IsGeneratorLibrary)' == 'true'">
-    <PackageReference Update="Microsoft.Generator.CSharp.ClientModel" Version="1.0.0-alpha.20241022.3" />
+    <PackageReference Update="Microsoft.Generator.CSharp.ClientModel" Version="1.0.0-alpha.20241030.4" />
   </ItemGroup>
 
   <!--
diff --git a/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpMessageProvider.cs b/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpMessageProvider.cs
index 43391c5ca039..95ffb0b02cd2 100644
--- a/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpMessageProvider.cs
+++ b/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpMessageProvider.cs
@@ -21,9 +21,6 @@ public HttpMessageProvider(ValueExpression original) : base(typeof(HttpMessage),
 
         public override CSharpType HttpMessageType => typeof(HttpMessage);
 
-        public override MethodBodyStatement Apply(ValueExpression options)
-            => MethodBodyStatement.Empty;
-
         public override ValueExpression BufferResponse()
             => Original.Property(nameof(HttpMessage.BufferResponse));
 
@@ -39,9 +36,12 @@ public override HttpRequestApi Request()
         public override HttpResponseApi Response()
             => new AzureResponseProvider(Original.Property(nameof(HttpMessage.Response)));
 
-        public override ValueExpression ResponseClassifier()
-            => Original.Property(nameof(HttpMessage.ResponseClassifier));
-
         public override HttpMessageApi ToExpression() => this;
+
+        public override MethodBodyStatement ApplyResponseClassifier(StatusCodeClassifierApi statusCodeClassifier)
+            => MethodBodyStatement.Empty;
+
+        public override MethodBodyStatement ApplyRequestOptions(HttpRequestOptionsApi options)
+            => MethodBodyStatement.Empty;
     }
 }
diff --git a/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpPipelineProvider.cs b/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpPipelineProvider.cs
index 5a1c2e40553c..05d90170eea4 100644
--- a/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpPipelineProvider.cs
+++ b/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpPipelineProvider.cs
@@ -6,6 +6,7 @@
 using Microsoft.Generator.CSharp.ClientModel.Providers;
 using Microsoft.Generator.CSharp.Expressions;
 using Microsoft.Generator.CSharp.Primitives;
+using Microsoft.Generator.CSharp.Statements;
 using static Microsoft.Generator.CSharp.Snippets.Snippet;
 
 namespace Azure.Generator.Providers.Abstraction
@@ -28,9 +29,6 @@ public HttpPipelineProvider(ValueExpression original) : base(typeof(HttpPipeline
         public override ValueExpression Create(ValueExpression options, ValueExpression perRetryPolicies)
             => Static(typeof(HttpPipelineBuilder)).Invoke(nameof(HttpPipelineBuilder.Build), [options, perRetryPolicies]);
 
-        public override HttpMessageApi CreateMessage()
-            => new HttpMessageProvider(Original.Invoke(nameof(HttpPipeline.CreateMessage)));
-
         public override ValueExpression CreateMessage(HttpRequestOptionsApi requestOptions, ValueExpression responseClassifier)
             => Original.Invoke(nameof(HttpPipeline.CreateMessage), requestOptions, responseClassifier).As<HttpMessage>();
 
@@ -40,12 +38,12 @@ public override ClientPipelineApi FromExpression(ValueExpression expression)
         public override ValueExpression PerRetryPolicy(params ValueExpression[] arguments)
             => Empty; // TODO: implement with default retry policy for Azure
 
-        public override InvokeMethodExpression Send(HttpMessageApi message)
-            => Original.Invoke(nameof(HttpPipeline.Send), [message, Default]);
+        public override ClientPipelineApi ToExpression() => this;
 
-        public override InvokeMethodExpression SendAsync(HttpMessageApi message)
-            => Original.Invoke(nameof(HttpPipeline.SendAsync), [message, Default], true);
+        public override MethodBodyStatement Send(HttpMessageApi message, HttpRequestOptionsApi options)
+            => Original.Invoke(nameof(HttpPipeline.Send), [message, Default]).Terminate();
 
-        public override ClientPipelineApi ToExpression() => this;
+        public override MethodBodyStatement SendAsync(HttpMessageApi message, HttpRequestOptionsApi options)
+            => Original.Invoke(nameof(HttpPipeline.SendAsync), [message, Default], true).Terminate();
     }
 }
diff --git a/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpRequestProvider.cs b/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpRequestProvider.cs
index 060ae8050a73..37f0f6278f65 100644
--- a/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpRequestProvider.cs
+++ b/eng/packages/http-client-csharp/generator/Azure.Generator/src/Providers/Abstraction/HttpRequestProvider.cs
@@ -4,7 +4,8 @@
 using Azure.Core;
 using Microsoft.Generator.CSharp.ClientModel.Providers;
 using Microsoft.Generator.CSharp.Expressions;
-using Microsoft.Generator.CSharp.Snippets;
+using Microsoft.Generator.CSharp.Statements;
+using System;
 using System.ClientModel.Primitives;
 using System.Collections.Generic;
 using static Microsoft.Generator.CSharp.Snippets.Snippet;
@@ -26,15 +27,79 @@ public override ValueExpression Content()
         public override HttpRequestApi FromExpression(ValueExpression original)
             => new HttpRequestProvider(original);
 
-        public override InvokeMethodExpression SetHeaders(IReadOnlyList<ValueExpression> arguments)
-            => Original.Property(nameof(PipelineRequest.Headers)).Invoke(nameof(RequestHeaders.Add), arguments);
+        public override MethodBodyStatement SetHeaders(IReadOnlyList<ValueExpression> arguments)
+            => Original.Property(nameof(PipelineRequest.Headers)).Invoke(nameof(RequestHeaders.SetValue), arguments).Terminate();
 
-        public override AssignmentExpression SetMethod(string httpMethod)
-            => Original.Property(nameof(PipelineRequest.Method)).Assign(New.Instance(typeof(RequestMethod), [Literal(httpMethod)]));
+        public override MethodBodyStatement SetMethod(string httpMethod)
+            => Original.Property(nameof(PipelineRequest.Method)).Assign(CreateRequestMethod(httpMethod)).Terminate();
 
-        public override AssignmentExpression SetUri(ValueExpression value)
-            => Original.Property("Uri").Assign(value);
+        public override MethodBodyStatement SetUri(ValueExpression value)
+            => Original.Property("Uri").Assign(value).Terminate();
 
         public override HttpRequestApi ToExpression() => this;
+
+        private ValueExpression CreateRequestMethod(string httpMethod)
+        {
+            var httpMethodString = ParseHttpMethodString(httpMethod);
+            return httpMethodString is null
+                ? New.Instance(typeof(RequestMethod), [Literal(httpMethod)])
+                : Static<RequestMethod>().Property(httpMethodString);
+        }
+
+        private string? ParseHttpMethodString(string method)
+        {
+            if (method == null)
+            {
+                throw new ArgumentNullException(nameof(method));
+            }
+            if (method.Length == 3)
+            {
+                if (string.Equals(method, "GET", StringComparison.OrdinalIgnoreCase))
+                {
+                    return "Get";
+                }
+
+                if (string.Equals(method, "PUT", StringComparison.OrdinalIgnoreCase))
+                {
+                    return "Put";
+                }
+            }
+            else if (method.Length == 4)
+            {
+                if (string.Equals(method, "POST", StringComparison.OrdinalIgnoreCase))
+                {
+                    return "Post";
+                }
+
+                if (string.Equals(method, "HEAD", StringComparison.OrdinalIgnoreCase))
+                {
+                    return "Head";
+                }
+            }
+            else
+            {
+                if (string.Equals(method, "PATCH", StringComparison.OrdinalIgnoreCase))
+                {
+                    return "Patch";
+                }
+
+                if (string.Equals(method, "DELETE", StringComparison.OrdinalIgnoreCase))
+                {
+                    return "Delete";
+                }
+
+                if (string.Equals(method, "OPTIONS", StringComparison.OrdinalIgnoreCase))
+                {
+                    return "Options";
+                }
+
+                if (string.Equals(method, "TRACE", StringComparison.OrdinalIgnoreCase))
+                {
+                    return "Trace";
+                }
+            }
+
+            return null;
+        }
     }
 }
diff --git a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/BasicTypeSpecClient.RestClient.cs b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/BasicTypeSpecClient.RestClient.cs
index 8f3177cdbe6a..eb6682ff07e3 100644
--- a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/BasicTypeSpecClient.RestClient.cs
+++ b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/BasicTypeSpecClient.RestClient.cs
@@ -15,21 +15,23 @@ namespace BasicTypeSpec
     public partial class BasicTypeSpecClient
     {
         private static ResponseClassifier _pipelineMessageClassifier200;
+        private static ResponseClassifier _pipelineMessageClassifier201;
         private static ResponseClassifier _pipelineMessageClassifier204;
         private static Classifier2xxAnd4xx _pipelineMessageClassifier2xxAnd4xx;
 
         private static ResponseClassifier PipelineMessageClassifier200 => _pipelineMessageClassifier200 = new StatusCodeClassifier(stackalloc ushort[] { 200 });
 
+        private static ResponseClassifier PipelineMessageClassifier201 => _pipelineMessageClassifier201 = new StatusCodeClassifier(stackalloc ushort[] { 201 });
+
         private static ResponseClassifier PipelineMessageClassifier204 => _pipelineMessageClassifier204 = new StatusCodeClassifier(stackalloc ushort[] { 204 });
 
         private static Classifier2xxAnd4xx PipelineMessageClassifier2xxAnd4xx => _pipelineMessageClassifier2xxAnd4xx ??= new Classifier2xxAnd4xx();
 
         internal HttpMessage CreateSayHiRequest(string headParameter, string queryParameter, string optionalQuery, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("GET");
+            request.Method = RequestMethod.Get;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/hello", false);
@@ -39,251 +41,235 @@ internal HttpMessage CreateSayHiRequest(string headParameter, string queryParame
                 uri.AppendQuery("optionalQuery", optionalQuery, true);
             }
             request.Uri = uri;
-            request.Headers.Add("head-parameter", headParameter);
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("head-parameter", headParameter);
+            request.Headers.SetValue("Accept", "application/json");
             return message;
         }
 
         internal HttpMessage CreateHelloAgainRequest(string p2, string p1, RequestContent content, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("GET");
+            request.Method = RequestMethod.Get;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/againHi/", false);
             uri.AppendPath(p2, true);
             request.Uri = uri;
-            request.Headers.Add("p1", p1);
-            request.Headers.Add("Content-Type", "text/plain");
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("p1", p1);
+            request.Headers.SetValue("Content-Type", "text/plain");
+            request.Headers.SetValue("Accept", "application/json");
             request.Content = content;
             return message;
         }
 
         internal HttpMessage CreateNoContentTypeRequest(string p2, string p1, RequestContent content, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("GET");
+            request.Method = RequestMethod.Get;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/noContentType/", false);
             uri.AppendPath(p2, true);
             request.Uri = uri;
-            request.Headers.Add("p1", p1);
-            request.Headers.Add("Content-Type", "application/json");
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("p1", p1);
+            request.Headers.SetValue("Content-Type", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             request.Content = content;
             return message;
         }
 
         internal HttpMessage CreateHelloDemo2Request(RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("GET");
+            request.Method = RequestMethod.Get;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/demoHi", false);
             request.Uri = uri;
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             return message;
         }
 
         internal HttpMessage CreateCreateLiteralRequest(RequestContent content, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("POST");
+            request.Method = RequestMethod.Post;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/literal", false);
             request.Uri = uri;
-            request.Headers.Add("Content-Type", "application/json");
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("Content-Type", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             request.Content = content;
             return message;
         }
 
         internal HttpMessage CreateHelloLiteralRequest(RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("GET");
+            request.Method = RequestMethod.Get;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/helloLiteral/", false);
             uri.AppendPath(123.ToString(), true);
             uri.AppendQuery("p3", TypeFormatters.ConvertToString(true, null), true);
             request.Uri = uri;
-            request.Headers.Add("p1", "test");
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("p1", "test");
+            request.Headers.SetValue("Accept", "application/json");
             return message;
         }
 
         internal HttpMessage CreateTopActionRequest(DateTimeOffset action, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("GET");
+            request.Method = RequestMethod.Get;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/top/", false);
             uri.AppendPath(action.ToString("O"), true);
             request.Uri = uri;
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             return message;
         }
 
         internal HttpMessage CreateTopAction2Request(RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("GET");
+            request.Method = RequestMethod.Get;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/top2", false);
             request.Uri = uri;
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             return message;
         }
 
         internal HttpMessage CreatePatchActionRequest(RequestContent content, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("PATCH");
+            request.Method = RequestMethod.Patch;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/patch", false);
             request.Uri = uri;
-            request.Headers.Add("Content-Type", "application/json");
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("Content-Type", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             request.Content = content;
             return message;
         }
 
         internal HttpMessage CreateAnonymousBodyRequest(RequestContent content, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("POST");
+            request.Method = RequestMethod.Post;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/anonymousBody", false);
             request.Uri = uri;
-            request.Headers.Add("Content-Type", "application/json");
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("Content-Type", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             request.Content = content;
             return message;
         }
 
         internal HttpMessage CreateFriendlyModelRequest(RequestContent content, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("POST");
+            request.Method = RequestMethod.Post;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/friendlyName", false);
             request.Uri = uri;
-            request.Headers.Add("Content-Type", "application/json");
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("Content-Type", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             request.Content = content;
             return message;
         }
 
         internal HttpMessage CreateAddTimeHeaderRequest(RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier204;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier204);
             Request request = message.Request;
-            request.Method = new RequestMethod("GET");
+            request.Method = RequestMethod.Get;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/", false);
             request.Uri = uri;
-            request.Headers.Add("Repeatability-First-Sent", TypeFormatters.ConvertToString(DateTimeOffset.Now, "R"));
+            request.Headers.SetValue("Repeatability-First-Sent", TypeFormatters.ConvertToString(DateTimeOffset.Now, "R"));
             return message;
         }
 
         internal HttpMessage CreateProjectedNameModelRequest(RequestContent content, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("POST");
+            request.Method = RequestMethod.Post;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/projectedName", false);
             request.Uri = uri;
-            request.Headers.Add("Content-Type", "application/json");
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("Content-Type", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             request.Content = content;
             return message;
         }
 
         internal HttpMessage CreateReturnsAnonymousModelRequest(RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("POST");
+            request.Method = RequestMethod.Post;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/returnsAnonymousModel", false);
             request.Uri = uri;
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             return message;
         }
 
         internal HttpMessage CreateGetUnknownValueRequest(string accept, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("GET");
+            request.Method = RequestMethod.Get;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/unknown-value", false);
             request.Uri = uri;
-            request.Headers.Add("Accept", accept);
+            request.Headers.SetValue("Accept", accept);
             return message;
         }
 
         internal HttpMessage CreateInternalProtocolRequest(RequestContent content, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier200;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier200);
             Request request = message.Request;
-            request.Method = new RequestMethod("POST");
+            request.Method = RequestMethod.Post;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/internalProtocol", false);
             request.Uri = uri;
-            request.Headers.Add("Content-Type", "application/json");
-            request.Headers.Add("Accept", "application/json");
+            request.Headers.SetValue("Content-Type", "application/json");
+            request.Headers.SetValue("Accept", "application/json");
             request.Content = content;
             return message;
         }
 
         internal HttpMessage CreateStillConvenientRequest(RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier204;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier204);
             Request request = message.Request;
-            request.Method = new RequestMethod("GET");
+            request.Method = RequestMethod.Get;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/stillConvenient", false);
@@ -293,10 +279,9 @@ internal HttpMessage CreateStillConvenientRequest(RequestContext context)
 
         internal HttpMessage CreateHeadAsBooleanRequest(string id, RequestContext context)
         {
-            HttpMessage message = Pipeline.CreateMessage();
-            message.ResponseClassifier = PipelineMessageClassifier2xxAnd4xx;
+            HttpMessage message = Pipeline.CreateMessage(context, PipelineMessageClassifier2xxAnd4xx);
             Request request = message.Request;
-            request.Method = new RequestMethod("HEAD");
+            request.Method = RequestMethod.Head;
             ClientUriBuilder uri = new ClientUriBuilder();
             uri.Reset(_endpoint);
             uri.AppendPath("/headAsBoolean/", false);
diff --git a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/BasicTypeSpecModelFactory.cs b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/BasicTypeSpecModelFactory.cs
index b52d06da39c9..c14a249fd60e 100644
--- a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/BasicTypeSpecModelFactory.cs
+++ b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/BasicTypeSpecModelFactory.cs
@@ -49,7 +49,7 @@ public static Thing Thing(string name = default, BinaryData requiredUnion = defa
                 requiredBadDescription,
                 optionalNullableList?.ToList(),
                 requiredNullableList?.ToList(),
-                null);
+                additionalBinaryDataProperties: null);
         }
 
         /// <summary> this is a roundtrip model. </summary>
@@ -116,7 +116,7 @@ public static RoundTripModel RoundTripModel(string requiredString = default, int
                 readOnlyOptionalRecordUnknown,
                 modelWithRequiredNullable,
                 requiredBytes,
-                null);
+                additionalBinaryDataProperties: null);
         }
 
         /// <summary> A model with a few required nullable properties. </summary>
@@ -127,7 +127,7 @@ public static RoundTripModel RoundTripModel(string requiredString = default, int
         public static ModelWithRequiredNullableProperties ModelWithRequiredNullableProperties(int? requiredNullablePrimitive = default, StringExtensibleEnum? requiredExtensibleEnum = default, StringFixedEnum? requiredFixedEnum = default)
         {
 
-            return new ModelWithRequiredNullableProperties(requiredNullablePrimitive, requiredExtensibleEnum, requiredFixedEnum, null);
+            return new ModelWithRequiredNullableProperties(requiredNullablePrimitive, requiredExtensibleEnum, requiredFixedEnum, additionalBinaryDataProperties: null);
         }
 
         /// <summary> this is not a friendly model but with a friendly name. </summary>
@@ -136,7 +136,7 @@ public static ModelWithRequiredNullableProperties ModelWithRequiredNullablePrope
         public static Friend Friend(string name = default)
         {
 
-            return new Friend(name, null);
+            return new Friend(name, additionalBinaryDataProperties: null);
         }
 
         /// <summary> this is a model with a projected name. </summary>
@@ -145,7 +145,7 @@ public static Friend Friend(string name = default)
         public static ProjectedModel ProjectedModel(string name = default)
         {
 
-            return new ProjectedModel(name, null);
+            return new ProjectedModel(name, additionalBinaryDataProperties: null);
         }
 
         /// <summary> The ReturnsAnonymousModelResponse. </summary>
@@ -153,7 +153,7 @@ public static ProjectedModel ProjectedModel(string name = default)
         public static ReturnsAnonymousModelResponse ReturnsAnonymousModelResponse()
         {
 
-            return new ReturnsAnonymousModelResponse(null);
+            return new ReturnsAnonymousModelResponse(additionalBinaryDataProperties: null);
         }
     }
 }
diff --git a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Internal/ClientPipelineExtensions.cs b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Internal/ClientPipelineExtensions.cs
index 82e2f9dcaead..0df6739148f7 100644
--- a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Internal/ClientPipelineExtensions.cs
+++ b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Internal/ClientPipelineExtensions.cs
@@ -14,11 +14,11 @@ namespace BasicTypeSpec
 {
     internal static partial class ClientPipelineExtensions
     {
-        public static async ValueTask<Response> ProcessMessageAsync(this HttpPipeline pipeline, HttpMessage message, RequestContext options)
+        public static async ValueTask<Response> ProcessMessageAsync(this HttpPipeline pipeline, HttpMessage message, RequestContext context)
         {
             await pipeline.SendAsync(message, default).ConfigureAwait(false);
 
-            if (message.Response.IsError && (options?.ErrorOptions & ErrorOptions.NoThrow) != ErrorOptions.NoThrow)
+            if (message.Response.IsError && (context?.ErrorOptions & ErrorOptions.NoThrow) != ErrorOptions.NoThrow)
             {
                 throw new RequestFailedException(message.Response);
             }
@@ -27,11 +27,11 @@ public static async ValueTask<Response> ProcessMessageAsync(this HttpPipeline pi
             return response;
         }
 
-        public static Response ProcessMessage(this HttpPipeline pipeline, HttpMessage message, RequestContext options)
+        public static Response ProcessMessage(this HttpPipeline pipeline, HttpMessage message, RequestContext context)
         {
             pipeline.Send(message, default);
 
-            if (message.Response.IsError && (options?.ErrorOptions & ErrorOptions.NoThrow) != ErrorOptions.NoThrow)
+            if (message.Response.IsError && (context?.ErrorOptions & ErrorOptions.NoThrow) != ErrorOptions.NoThrow)
             {
                 throw new RequestFailedException(message.Response);
             }
@@ -40,9 +40,9 @@ public static Response ProcessMessage(this HttpPipeline pipeline, HttpMessage me
             return response;
         }
 
-        public static async ValueTask<Response<bool>> ProcessHeadAsBoolMessageAsync(this HttpPipeline pipeline, HttpMessage message, RequestContext options)
+        public static async ValueTask<Response<bool>> ProcessHeadAsBoolMessageAsync(this HttpPipeline pipeline, HttpMessage message, RequestContext context)
         {
-            Response response = await pipeline.ProcessMessageAsync(message, options).ConfigureAwait(false);
+            Response response = await pipeline.ProcessMessageAsync(message, context).ConfigureAwait(false);
             switch (response.Status)
             {
                 case >= 200 and < 300:
@@ -54,9 +54,9 @@ public static async ValueTask<Response<bool>> ProcessHeadAsBoolMessageAsync(this
             }
         }
 
-        public static Response<bool> ProcessHeadAsBoolMessage(this HttpPipeline pipeline, HttpMessage message, RequestContext options)
+        public static Response<bool> ProcessHeadAsBoolMessage(this HttpPipeline pipeline, HttpMessage message, RequestContext context)
         {
-            Response response = pipeline.ProcessMessage(message, options);
+            Response response = pipeline.ProcessMessage(message, context);
             switch (response.Status)
             {
                 case >= 200 and < 300:
diff --git a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/Friend.Serialization.cs b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/Friend.Serialization.cs
index f92833ee37f3..4f53647f4410 100644
--- a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/Friend.Serialization.cs
+++ b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/Friend.Serialization.cs
@@ -134,6 +134,10 @@ protected virtual Friend PersistableModelCreateCore(BinaryData data, ModelReader
         /// <param name="friend"> The <see cref="Friend"/> to serialize into <see cref="RequestContent"/>. </param>
         public static implicit operator RequestContent(Friend friend)
         {
+            if (friend == null)
+            {
+                return null;
+            }
             Utf8JsonBinaryContent content = new Utf8JsonBinaryContent();
             content.JsonWriter.WriteObjectValue(friend, ModelSerializationExtensions.WireOptions);
             return content;
diff --git a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ModelWithRequiredNullableProperties.Serialization.cs b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ModelWithRequiredNullableProperties.Serialization.cs
index baa17dbaa1cb..b750c8647796 100644
--- a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ModelWithRequiredNullableProperties.Serialization.cs
+++ b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ModelWithRequiredNullableProperties.Serialization.cs
@@ -186,6 +186,10 @@ protected virtual ModelWithRequiredNullableProperties PersistableModelCreateCore
         /// <param name="modelWithRequiredNullableProperties"> The <see cref="ModelWithRequiredNullableProperties"/> to serialize into <see cref="RequestContent"/>. </param>
         public static implicit operator RequestContent(ModelWithRequiredNullableProperties modelWithRequiredNullableProperties)
         {
+            if (modelWithRequiredNullableProperties == null)
+            {
+                return null;
+            }
             Utf8JsonBinaryContent content = new Utf8JsonBinaryContent();
             content.JsonWriter.WriteObjectValue(modelWithRequiredNullableProperties, ModelSerializationExtensions.WireOptions);
             return content;
diff --git a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ProjectedModel.Serialization.cs b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ProjectedModel.Serialization.cs
index 75dc1aad68de..fc83f20f07aa 100644
--- a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ProjectedModel.Serialization.cs
+++ b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ProjectedModel.Serialization.cs
@@ -134,6 +134,10 @@ protected virtual ProjectedModel PersistableModelCreateCore(BinaryData data, Mod
         /// <param name="projectedModel"> The <see cref="ProjectedModel"/> to serialize into <see cref="RequestContent"/>. </param>
         public static implicit operator RequestContent(ProjectedModel projectedModel)
         {
+            if (projectedModel == null)
+            {
+                return null;
+            }
             Utf8JsonBinaryContent content = new Utf8JsonBinaryContent();
             content.JsonWriter.WriteObjectValue(projectedModel, ModelSerializationExtensions.WireOptions);
             return content;
diff --git a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ReturnsAnonymousModelResponse.Serialization.cs b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ReturnsAnonymousModelResponse.Serialization.cs
index 092802278552..999c8993fbf5 100644
--- a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ReturnsAnonymousModelResponse.Serialization.cs
+++ b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/ReturnsAnonymousModelResponse.Serialization.cs
@@ -122,6 +122,10 @@ protected virtual ReturnsAnonymousModelResponse PersistableModelCreateCore(Binar
         /// <param name="returnsAnonymousModelResponse"> The <see cref="ReturnsAnonymousModelResponse"/> to serialize into <see cref="RequestContent"/>. </param>
         public static implicit operator RequestContent(ReturnsAnonymousModelResponse returnsAnonymousModelResponse)
         {
+            if (returnsAnonymousModelResponse == null)
+            {
+                return null;
+            }
             Utf8JsonBinaryContent content = new Utf8JsonBinaryContent();
             content.JsonWriter.WriteObjectValue(returnsAnonymousModelResponse, ModelSerializationExtensions.WireOptions);
             return content;
diff --git a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/RoundTripModel.Serialization.cs b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/RoundTripModel.Serialization.cs
index 62467f32c0fe..d3c11e295c7e 100644
--- a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/RoundTripModel.Serialization.cs
+++ b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/RoundTripModel.Serialization.cs
@@ -352,7 +352,6 @@ internal static RoundTripModel DeserializeRoundTripModel(JsonElement element, Mo
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        intExtensibleEnum = null;
                         continue;
                     }
                     intExtensibleEnum = new IntExtensibleEnum(prop.Value.GetInt32());
@@ -376,7 +375,6 @@ internal static RoundTripModel DeserializeRoundTripModel(JsonElement element, Mo
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        floatExtensibleEnum = null;
                         continue;
                     }
                     floatExtensibleEnum = new FloatExtensibleEnum(prop.Value.GetSingle());
@@ -386,7 +384,6 @@ internal static RoundTripModel DeserializeRoundTripModel(JsonElement element, Mo
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        floatExtensibleEnumWithIntValue = null;
                         continue;
                     }
                     floatExtensibleEnumWithIntValue = new FloatExtensibleEnumWithIntValue(prop.Value.GetSingle());
@@ -410,7 +407,6 @@ internal static RoundTripModel DeserializeRoundTripModel(JsonElement element, Mo
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        floatFixedEnum = null;
                         continue;
                     }
                     floatFixedEnum = prop.Value.GetSingle().ToFloatFixedEnum();
@@ -420,7 +416,6 @@ internal static RoundTripModel DeserializeRoundTripModel(JsonElement element, Mo
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        floatFixedEnumWithIntValue = null;
                         continue;
                     }
                     floatFixedEnumWithIntValue = prop.Value.GetInt32().ToFloatFixedEnumWithIntValue();
@@ -444,7 +439,6 @@ internal static RoundTripModel DeserializeRoundTripModel(JsonElement element, Mo
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        intFixedEnum = null;
                         continue;
                     }
                     intFixedEnum = prop.Value.GetInt32().ToIntFixedEnum();
@@ -468,7 +462,6 @@ internal static RoundTripModel DeserializeRoundTripModel(JsonElement element, Mo
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        stringFixedEnum = null;
                         continue;
                     }
                     stringFixedEnum = prop.Value.GetString().ToStringFixedEnum();
@@ -483,7 +476,6 @@ internal static RoundTripModel DeserializeRoundTripModel(JsonElement element, Mo
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        optionalUnknown = null;
                         continue;
                     }
                     optionalUnknown = BinaryData.FromString(prop.Value.GetRawText());
@@ -647,6 +639,10 @@ protected virtual RoundTripModel PersistableModelCreateCore(BinaryData data, Mod
         /// <param name="roundTripModel"> The <see cref="RoundTripModel"/> to serialize into <see cref="RequestContent"/>. </param>
         public static implicit operator RequestContent(RoundTripModel roundTripModel)
         {
+            if (roundTripModel == null)
+            {
+                return null;
+            }
             Utf8JsonBinaryContent content = new Utf8JsonBinaryContent();
             content.JsonWriter.WriteObjectValue(roundTripModel, ModelSerializationExtensions.WireOptions);
             return content;
diff --git a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/Thing.Serialization.cs b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/Thing.Serialization.cs
index c473fa19a5fa..d67702d57298 100644
--- a/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/Thing.Serialization.cs
+++ b/eng/packages/http-client-csharp/generator/TestProjects/Local/Basic-TypeSpec/src/Generated/Models/Thing.Serialization.cs
@@ -198,7 +198,6 @@ internal static Thing DeserializeThing(JsonElement element, ModelReaderWriterOpt
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        optionalLiteralString = null;
                         continue;
                     }
                     optionalLiteralString = new ThingOptionalLiteralString(prop.Value.GetString());
@@ -208,7 +207,6 @@ internal static Thing DeserializeThing(JsonElement element, ModelReaderWriterOpt
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        optionalLiteralInt = null;
                         continue;
                     }
                     optionalLiteralInt = new ThingOptionalLiteralInt(prop.Value.GetInt32());
@@ -218,7 +216,6 @@ internal static Thing DeserializeThing(JsonElement element, ModelReaderWriterOpt
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        optionalLiteralFloat = null;
                         continue;
                     }
                     optionalLiteralFloat = new ThingOptionalLiteralFloat(prop.Value.GetSingle());
@@ -228,7 +225,6 @@ internal static Thing DeserializeThing(JsonElement element, ModelReaderWriterOpt
                 {
                     if (prop.Value.ValueKind == JsonValueKind.Null)
                     {
-                        optionalLiteralBool = null;
                         continue;
                     }
                     optionalLiteralBool = prop.Value.GetBoolean();
@@ -329,6 +325,10 @@ protected virtual Thing PersistableModelCreateCore(BinaryData data, ModelReaderW
         /// <param name="thing"> The <see cref="Thing"/> to serialize into <see cref="RequestContent"/>. </param>
         public static implicit operator RequestContent(Thing thing)
         {
+            if (thing == null)
+            {
+                return null;
+            }
             Utf8JsonBinaryContent content = new Utf8JsonBinaryContent();
             content.JsonWriter.WriteObjectValue(thing, ModelSerializationExtensions.WireOptions);
             return content;
diff --git a/eng/scripts/typespec/Generate-Code.ps1 b/eng/scripts/typespec/Generate-Code.ps1
index fd87c760daa1..b71faf54942a 100644
--- a/eng/scripts/typespec/Generate-Code.ps1
+++ b/eng/scripts/typespec/Generate-Code.ps1
@@ -36,6 +36,8 @@ function Refresh-Build {
 $testProjectsLocalDir = Join-Path $packageRoot 'generator' 'TestProjects' 'Local'
 $basicTypespecTestProject = Join-Path $testProjectsLocalDir "Basic-TypeSpec"
 
+Push-Location $packageRoot
+
 Write-Host "Generating test projects ..."
 Refresh-Build
 
@@ -45,4 +47,6 @@ Invoke-LoggedCommand (Get-TspCommand "$basicTypespecTestProject/Basic-TypeSpec.t
 Write-Host "Building BasicTypeSpec" -ForegroundColor Cyan
 Invoke-LoggedCommand "dotnet build $packageRoot/generator/TestProjects/Local/Basic-TypeSpec/src/BasicTypeSpec.csproj"
 
+Pop-Location
+
 Write-Host 'Code generation is completed.'