Enable property visibility tests in source-gen mode (#54526)

* Enable property visibility tests in source-gen mode

* Address feedback

* Fix S.N.H.Json tests

* Fix S.T.J tests

* Fix S.N.H.J tests ii

Author: layomia

src/libraries/System.Net.Http.Json/tests/FunctionalTests/JsonContext/Person.cs

@@ -47,51 +47,63 @@ private static JsonPropertyInfo[] PersonPropInitFunc(JsonSerializerContext conte
             properties[0] = JsonMetadataServices.CreatePropertyInfo(
                 options,
                 isProperty: true,
+                isPublic: true,
+                isVirtual: false,
                 declaringType: typeof(Person),
                 propertyTypeInfo: jsonContext.Int32,
                 converter: null,
                 getter: static (obj) => { return ((Person)obj).Age; },
                 setter: static (obj, value) => { ((Person)obj).Age = value; },
                 ignoreCondition: default,
+                hasJsonInclude: false,
                 numberHandling: default,
                 propertyName: nameof(Tests.Person.Age),
                 jsonPropertyName: null);
 
             properties[1] = JsonMetadataServices.CreatePropertyInfo(
                 options,
                 isProperty: true,
+                isPublic: true,
+                isVirtual: false,
                 declaringType: typeof(Person),
                 propertyTypeInfo: jsonContext.String,
                 converter: null,
                 getter: static (obj) => { return ((Person)obj).Name; },
                 setter: static (obj, value) => { ((Person)obj).Name = value; },
                 ignoreCondition: default,
+                hasJsonInclude: false,
                 numberHandling: default,
                 propertyName: nameof(Tests.Person.Name),
                 jsonPropertyName: null);
 
             properties[2] = JsonMetadataServices.CreatePropertyInfo(
                 options,
                 isProperty: true,
+                isPublic: true,
+                isVirtual: false,
                 declaringType: typeof(Person),
                 propertyTypeInfo: jsonContext.Person,
                 converter: null,
                 getter: static (obj) => { return ((Person)obj).Parent; },
                 setter: static (obj, value) => { ((Person)obj).Parent = value; },
                 ignoreCondition: default,
+                hasJsonInclude: false,
                 numberHandling: default,
                 propertyName: nameof(Tests.Person.Parent),
                 jsonPropertyName: null);
 
             properties[3] = JsonMetadataServices.CreatePropertyInfo(
                 options,
                 isProperty: true,
+                isPublic: true,
+                isVirtual: false,
                 declaringType: typeof(Person),
                 propertyTypeInfo: jsonContext.String,
                 converter: null,
                 getter: static (obj) => { return ((Person)obj).PlaceOfBirth; },
                 setter: static (obj, value) => { ((Person)obj).PlaceOfBirth = value; },
                 ignoreCondition: default,
+                hasJsonInclude: false,
                 numberHandling: default,
                 propertyName: nameof(Tests.Person.PlaceOfBirth),
                 jsonPropertyName: null);

src/libraries/System.Text.Json/Common/JsonHelpers.cs

@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Generic;
+
+namespace System.Text.Json
+{
+    internal static partial class JsonHelpers
+    {
+        /// <summary>
+        /// Emulates Dictionary.TryAdd on netstandard.
+        /// </summary>
+        public static bool TryAdd<TKey, TValue>(this Dictionary<TKey, TValue> dictionary, in TKey key, in TValue value) where TKey : notnull
+        {
+#if NETSTANDARD2_0 || NETFRAMEWORK
+            if (!dictionary.ContainsKey(key))
+            {
+                dictionary[key] = value;
+                return true;
+            }
+
+            return false;
+#else
+            return dictionary.TryAdd(key, value);
+#endif
+        }
+    }
+}

src/libraries/System.Text.Json/Common/ReflectionExtensions.cs

@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics;
+using System.Reflection;
+
+namespace System.Text.Json.Reflection
+{
+    internal static partial class ReflectionExtensions
+    {
+        public static bool IsVirtual(this PropertyInfo? propertyInfo)
+        {
+            Debug.Assert(propertyInfo != null);
+            return propertyInfo != null && (propertyInfo.GetMethod?.IsVirtual == true || propertyInfo.SetMethod?.IsVirtual == true);
+        }
+    }
+}

src/libraries/System.Text.Json/gen/ContextGenerationSpec.cs

@@ -3,7 +3,7 @@
 
 using System.Collections.Generic;
 using System.Text.Json.Serialization;
-using System.Text.Json.SourceGeneration.Reflection;
+using System.Text.Json.Reflection;
 
 namespace System.Text.Json.SourceGeneration
 {
@@ -19,6 +19,8 @@ internal sealed class ContextGenerationSpec
 
         public List<TypeGenerationSpec> RootSerializableTypes { get; } = new();
 
+        public HashSet<TypeGenerationSpec>? NullableUnderlyingTypes { get; } = new();
+
         public List<string> ContextClassDeclarationList { get; init; }
 
         /// <summary>