Make source generated JsonTypeInfo properties nullable-oblivious

src/libraries/System.Text.Json/gen/JsonSourceGenerator.Emitter.cs

@@ -3,12 +3,10 @@
 
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Globalization;
 using System.Linq;
 using System.Reflection;
 using System.Text.Json.Serialization;
 using Microsoft.CodeAnalysis;
-using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.Text;
 using SourceGenerators;
 
@@ -1009,7 +1007,9 @@ private static void GenerateTypeInfoFactoryHeader(SourceWriter writer, TypeGener
                     /// <summary>
                     /// Defines the source generated JSON serialization contract metadata for a given type.
                     /// </summary>
+                    #nullable disable annotations // Marking the property type as nullable-oblivious.
                     public {{typeInfoFQN}} {{typeInfoPropertyName}}
+                    #nullable enable annotations
                     {
                         get => _{{typeInfoPropertyName}} ??= ({{typeInfoFQN}}){{OptionsInstanceVariableName}}.GetTypeInfo(typeof({{typeFQN}}));
                     }

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Unit.Tests/JsonSourceGeneratorTests.cs

@@ -737,5 +737,36 @@ public class MyClass
             Compilation compilation = CompilationHelper.CreateCompilation(source, parseOptions: CompilationHelper.CreateParseOptions(languageVersion));
             CompilationHelper.RunJsonSourceGenerator(compilation);
         }
+
+        [Fact]
+        public void DoesNotWarnOnNullabilityMismatch()
+        {
+            string source = $$"""
+                using System.Collections.Generic;
+                using System.Text.Json;
+                using System.Text.Json.Serialization;
+                #nullable enable
+
+                namespace HelloWorld
+                {
+                    public static class MyClass
+                    {
+                        public static string Test()
+                        {
+                            Dictionary<int, string?> values = new();
+                            return JsonSerializer.Serialize(values, JsonContext.Default.DictionaryInt32String);
+                        }
+                    }
+
+                    [JsonSerializable(typeof(Dictionary<int, string>))]
+                    internal partial class JsonContext : JsonSerializerContext
+                    {
+                    }
+                }
+                """;
+
+            Compilation compilation = CompilationHelper.CreateCompilation(source);
+            CompilationHelper.RunJsonSourceGenerator(compilation);
+        }
     }
 }