Fixes some wrong method names, invalid enum values and correct deprec…

…ation annotation

src/Kiota.Builder/Writers/Dart/CodeEnumWriter.cs

@@ -1,9 +1,11 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 
 using Kiota.Builder.CodeDOM;
 using Kiota.Builder.Extensions;
 using Kiota.Builder.Refiners;
+using Microsoft.OpenApi.Any;
 
 namespace Kiota.Builder.Writers.Dart;
 public class CodeEnumWriter : BaseElementWriter<CodeEnum, DartConventionService>
@@ -23,20 +25,31 @@ public override void WriteCodeElement(CodeEnum codeElement, LanguageWriter write
         writer.StartBlock($"enum {enumName} {{");
         var lastOption = codeElement.Options.Last();
 
+        HashSet<String> usedNames = new HashSet<string>();
         foreach (var option in codeElement.Options)
         {
             conventions.WriteShortDescription(option, writer);
             var correctedName = getCorrectedName(option.Name);
-            if (reservedNamesProvider.ReservedNames.Contains(correctedName))
+            if (reservedNamesProvider.ReservedNames.Contains(correctedName) || IllegalEnumValue(correctedName))
             {
                 correctedName += "Escaped";
             }
+            if (!usedNames.Add(correctedName))
+            {
+                correctedName = option.Name;
+                usedNames.Add(correctedName);
+            }
             writer.WriteLine($"{correctedName}(\"{option.Name}\"){(option == lastOption ? ";" : ",")}");
         }
         writer.WriteLine($"const {enumName}(this.value);");
         writer.WriteLine("final String value;");
     }
 
+    private bool IllegalEnumValue(string correctedName)
+    {
+        return correctedName.EqualsIgnoreCase("string") || correctedName.EqualsIgnoreCase("index");
+    }
+
     private string getCorrectedName(string name)
     {
         if (name.Contains('_', StringComparison.Ordinal))

src/Kiota.Builder/Writers/Dart/CodeMethodWriter.cs

@@ -447,7 +447,7 @@ protected void WriteRequestExecutorBody(CodeMethod codeElement, RequestParams re
         };
         writer.WriteLine($"{prefix}await requestAdapter.{GetSendRequestMethodName(isVoid, codeElement, codeElement.ReturnType)}(requestInfo{returnTypeFactory}, {errorMappingVarName});");
         if (codeElement.ReturnType.IsCollection)
-            writer.WriteLine("return collectionResult?.ToList();");
+            writer.WriteLine("return collectionResult?.toList();");
     }
     private const string RequestInfoVarName = "requestInfo";
     private void WriteRequestGeneratorBody(CodeMethod codeElement, RequestParams requestParams, CodeClass currentClass, LanguageWriter writer)
@@ -479,7 +479,7 @@ private void WriteRequestGeneratorBody(CodeMethod codeElement, RequestParams req
             }
             else if (currentClass.GetPropertyOfKind(CodePropertyKind.RequestAdapter) is CodeProperty requestAdapterProperty)
                 if (requestParams.requestBody.Type is CodeType bodyType && (bodyType.TypeDefinition is CodeClass || bodyType.Name.Equals("MultipartBody", StringComparison.OrdinalIgnoreCase)))
-                    writer.WriteLine($"{RequestInfoVarName}.setContentFromParsable({requestAdapterProperty.Name.ToFirstCharacterLowerCase()}, \"{codeElement.RequestBodyContentType}\", {requestParams.requestBody.Name});");
+                    writer.WriteLine($"{RequestInfoVarName}.setContentFromParsable{suffix}({requestAdapterProperty.Name.ToFirstCharacterLowerCase()}, \"{codeElement.RequestBodyContentType}\", {requestParams.requestBody.Name});");
                 else
                     writer.WriteLine($"{RequestInfoVarName}.setContentFromScalar{suffix}({requestAdapterProperty.Name.ToFirstCharacterLowerCase()}, \"{codeElement.RequestBodyContentType}\", {requestParams.requestBody.Name});");
         }

src/Kiota.Builder/Writers/Dart/DartConventionService.cs

@@ -16,7 +16,7 @@ public class DartConventionService : CommonLanguageConventionService
     public override string StreamTypeName => "stream";
     public override string VoidTypeName => "void";
     public override string DocCommentPrefix => "/// ";
-    private static readonly HashSet<string> NullableTypes = new(StringComparer.OrdinalIgnoreCase) { "int", "bool", "double", "string", "datetime" };
+    private static readonly HashSet<string> NullableTypes = new(StringComparer.OrdinalIgnoreCase) { "int", "bool", "double", "string", "datetime", "dateonly", "timeonly" };
     public const char NullableMarker = '?';
     public static string NullableMarkerAsString => "?";
     public override string ParseNodeInterfaceName => "ParseNode";
@@ -313,14 +313,14 @@ _ when nameof(String).Equals(parameterType, StringComparison.OrdinalIgnoreCase)
         var close = !string.IsNullOrEmpty(defaultValue) ? "}" : "";
         return $"{GetDeprecationInformation(parameter)}{open}{parameterType} {parameter.Name.ToFirstCharacterLowerCase()}{defaultValue}{close}";
     }
-    private static string GetDeprecationInformation(IDeprecableElement element)
+    private string GetDeprecationInformation(IDeprecableElement element)
     {
         if (element.Deprecation is null || !element.Deprecation.IsDeprecated) return string.Empty;
 
         var versionComment = string.IsNullOrEmpty(element.Deprecation.Version) ? string.Empty : $" as of {element.Deprecation.Version}";
         var dateComment = element.Deprecation.Date is null ? string.Empty : $" on {element.Deprecation.Date.Value.Date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)}";
         var removalComment = element.Deprecation.RemovalDate is null ? string.Empty : $" and will be removed {element.Deprecation.RemovalDate.Value.Date.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)}";
-        return $"@obsolete(\"{element.Deprecation.GetDescription}{versionComment}{dateComment}{removalComment}\")";
+        return $"@Deprecated(\"{element.Deprecation.GetDescription(type => GetTypeString(type, (element as CodeElement)!))}{versionComment}{dateComment}{removalComment}\")";
     }
     internal void WriteDeprecationAttribute(IDeprecableElement element, LanguageWriter writer)
     {