Check if maxpagesize should be reinjected

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/RestClientProvider.cs

@@ -23,6 +23,7 @@ public class RestClientProvider : TypeProvider
     {
         private const string RepeatabilityRequestIdHeader = "Repeatability-Request-ID";
         private const string RepeatabilityFirstSentHeader = "Repeatability-First-Sent";
+        private const string MaxPageSizeParameterName = "maxpagesize";
 
         private static readonly Dictionary<string, ParameterProvider> _knownSpecialHeaderParams = new(StringComparer.OrdinalIgnoreCase)
         {
@@ -222,7 +223,7 @@ private MethodBodyStatements BuildMessage(
 
                 if (reinjectedParamsMap.Count > 0)
                 {
-                    statements.AddRange(AppendQueryParameters(uri, operation, reinjectedParamsMap));
+                    statements.AddRange(AppendQueryParameters(uri, operation, reinjectedParamsMap, isNextLinkRequest: true));
                 }
             }
             else
@@ -417,7 +418,7 @@ private IEnumerable<MethodBodyStatement> AppendHeaderParameters(HttpRequestApi r
             return statements;
         }
 
-        private static List<MethodBodyStatement> AppendQueryParameters(ScopedApi uri, InputOperation operation, Dictionary<string, ParameterProvider> paramMap)
+        private static List<MethodBodyStatement> AppendQueryParameters(ScopedApi uri, InputOperation operation, Dictionary<string, ParameterProvider> paramMap, bool isNextLinkRequest = false)
         {
             List<MethodBodyStatement> statements = new(operation.Parameters.Count);
 
@@ -426,7 +427,7 @@ private static List<MethodBodyStatement> AppendQueryParameters(ScopedApi uri, In
                 if (inputParameter is not InputQueryParameter inputQueryParameter)
                     continue;
 
-                var queryStatement = BuildQueryParameterStatement(uri, inputQueryParameter, paramMap, operation);
+                var queryStatement = BuildQueryParameterStatement(uri, inputQueryParameter, paramMap, operation, isNextLinkRequest);
                 if (queryStatement != null)
                 {
                     statements.Add(queryStatement);
@@ -440,7 +441,8 @@ private static List<MethodBodyStatement> AppendQueryParameters(ScopedApi uri, In
             ScopedApi uri,
             InputQueryParameter inputQueryParameter,
             Dictionary<string, ParameterProvider> paramMap,
-            InputOperation operation)
+            InputOperation operation,
+            bool isNextLinkRequest = false)
         {
             GetParamInfo(paramMap, operation, inputQueryParameter, out var paramType, out var serializationFormat, out var valueExpression);
             if (valueExpression == null)
@@ -450,6 +452,14 @@ private static List<MethodBodyStatement> AppendQueryParameters(ScopedApi uri, In
 
             var statement = BuildAppendQueryStatement(uri, inputQueryParameter, paramType, valueExpression, serializationFormat);
 
+            // Runtime check to avoid duplicate pagination parameters
+            if (isNextLinkRequest && ShouldSkipReinjectedParameter(inputQueryParameter.SerializedName))
+            {
+                var parameterExistsCheck = uri.Property("Query").Invoke("Contains", Literal($"{inputQueryParameter.SerializedName}="));
+                var conditionalStatement = new IfStatement(Not(parameterExistsCheck)) { statement };
+                statement = conditionalStatement;
+            }
+
             // Apply null check if needed
             if (!inputQueryParameter.IsRequired || paramType?.IsNullable == true ||
                 (paramType is { IsValueType: false, IsFrameworkType: true } && paramType.FrameworkType != typeof(string)))
@@ -802,6 +812,12 @@ private static bool TryGetSpecialHeaderParam(InputParameter inputParameter, [Not
             return false;
         }
 
+        private static bool ShouldSkipReinjectedParameter(string parameterName)
+        {
+            return parameterName.Equals(MaxPageSizeParameterName, StringComparison.OrdinalIgnoreCase);
+            // In the future, we can extend this to check multiple parameters
+        }
+
         private static List<int> GetSuccessStatusCodes(InputOperation operation)
         {
             HashSet<int> statusCodes = [];

packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/RestClientProviders/TestData/RestClientProviderTests/TestPageSizeParameterReinjectedInCreateNextRequestMethod.cs

@@ -34,7 +34,10 @@ public partial class TestClient
             uri.AppendQuery("p1", p1, true);
             if ((maxPageSize != null))
             {
-                uri.AppendQuery("maxPageSize", global::Sample.TypeFormatters.ConvertToString(maxPageSize), true);
+                if (!uri.Query.Contains("maxPageSize="))
+                {
+                    uri.AppendQuery("maxPageSize", global::Sample.TypeFormatters.ConvertToString(maxPageSize), true);
+                }
             }
             global::System.ClientModel.Primitives.PipelineMessage message = Pipeline.CreateMessage(uri.ToUri(), "GET", PipelineMessageClassifier200);
             global::System.ClientModel.Primitives.PipelineRequest request = message.Request;