Implement new metadata knobs as internal APIs

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

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Runtime.InteropServices;
 using System.Collections.Generic;
 
 namespace System.Text.Json
@@ -22,6 +23,42 @@ public static bool TryAdd<TKey, TValue>(this Dictionary<TKey, TValue> dictionary
             return false;
 #else
             return dictionary.TryAdd(key, value);
+#endif
+        }
+
+        /// <summary>
+        /// Provides an in-place, stable sorting implementation for List.
+        /// </summary>
+        internal static void StableSortByKey<T, TKey>(this List<T> items, Func<T, TKey> keySelector)
+            where TKey : unmanaged, IComparable<TKey>
+        {
+#if NET6_0_OR_GREATER
+            Span<T> span = CollectionsMarshal.AsSpan(items);
+
+            // Tuples implement lexical ordering OOTB which can be used to encode stable sorting
+            // using the actual key as the first element and index as the second element.
+            const int StackallocThreshold = 32;
+            Span<(TKey, int)> keys = span.Length <= StackallocThreshold
+                ? (stackalloc (TKey, int)[StackallocThreshold]).Slice(0, span.Length)
+                : new (TKey, int)[span.Length];
+
+            for (int i = 0; i < keys.Length; i++)
+            {
+                keys[i] = (keySelector(span[i]), i);
+            }
+
+            MemoryExtensions.Sort(keys, span);
+#else
+            T[] arrayCopy = items.ToArray();
+            (TKey, int)[] keys = new (TKey, int)[arrayCopy.Length];
+            for (int i = 0; i < keys.Length; i++)
+            {
+                keys[i] = (keySelector(arrayCopy[i]), i);
+            }
+
+            Array.Sort(keys, arrayCopy);
+            items.Clear();
+            items.AddRange(arrayCopy);
 #endif
         }
     }

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

@@ -4,7 +4,6 @@
 using System.Collections;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
@@ -16,7 +15,6 @@
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.DotnetRuntime.Extensions;
-using Microsoft.CodeAnalysis.Text;
 
 namespace System.Text.Json.SourceGeneration
 {

src/libraries/System.Text.Json/src/Resources/Strings.resx

@@ -668,4 +668,7 @@
   <data name="JsonPolymorphismOptionsAssociatedWithDifferentJsonTypeInfo" xml:space="preserve">
     <value>Parameter already associated with a different JsonTypeInfo instance.</value>
   </data>
+  <data name="SerializationCallbacksNotSupported" xml:space="preserve">
+    <value>Serialization callbacks are not supported in metadata kind '{0}'.</value>
+  </data>
 </root>

src/libraries/System.Text.Json/src/System.Text.Json.csproj

@@ -364,6 +364,7 @@ The System.Text.Json library is built-in as part of the shared framework in .NET
     <Reference Include="System.Reflection.Emit.Lightweight" />
     <Reference Include="System.Reflection.Primitives" />
     <Reference Include="System.Runtime" />
+    <Reference Include="System.Runtime.InteropServices" />
     <Reference Include="System.Runtime.Loader" />
     <Reference Include="System.Text.Encoding.Extensions" />
     <Reference Include="System.Threading" />

src/libraries/System.Text.Json/src/System/Text/Json/JsonPropertyDictionary.KeyCollection.cs

@@ -30,7 +30,7 @@ public KeyCollection(JsonPropertyDictionary<T> jsonObject)
 
             IEnumerator IEnumerable.GetEnumerator()
             {
-                foreach (KeyValuePair<string, T?> item in _parent)
+                foreach (KeyValuePair<string, T> item in _parent)
                 {
                     yield return item.Key;
                 }
@@ -49,7 +49,7 @@ public void CopyTo(string[] propertyNameArray, int index)
                     ThrowHelper.ThrowArgumentOutOfRangeException_ArrayIndexNegative(nameof(index));
                 }
 
-                foreach (KeyValuePair<string, T?> item in _parent)
+                foreach (KeyValuePair<string, T> item in _parent)
                 {
                     if (index >= propertyNameArray.Length)
                     {
@@ -62,7 +62,7 @@ public void CopyTo(string[] propertyNameArray, int index)
 
             public IEnumerator<string> GetEnumerator()
             {
-                foreach (KeyValuePair<string, T?> item in _parent)
+                foreach (KeyValuePair<string, T> item in _parent)
                 {
                     yield return item.Key;
                 }

src/libraries/System.Text.Json/src/System/Text/Json/JsonPropertyDictionary.ValueCollection.cs

@@ -10,12 +10,12 @@ internal sealed partial class JsonPropertyDictionary<T>
     {
         private ValueCollection? _valueCollection;
 
-        public ICollection<T?> GetValueCollection()
+        public ICollection<T> GetValueCollection()
         {
             return _valueCollection ??= new ValueCollection(this);
         }
 
-        private sealed class ValueCollection : ICollection<T?>
+        private sealed class ValueCollection : ICollection<T>
         {
             private readonly JsonPropertyDictionary<T> _parent;
 
@@ -30,26 +30,26 @@ public ValueCollection(JsonPropertyDictionary<T> jsonObject)
 
             IEnumerator IEnumerable.GetEnumerator()
             {
-                foreach (KeyValuePair<string, T?> item in _parent)
+                foreach (KeyValuePair<string, T> item in _parent)
                 {
                     yield return item.Value;
                 }
             }
 
-            public void Add(T? jsonNode) => ThrowHelper.ThrowNotSupportedException_CollectionIsReadOnly();
+            public void Add(T jsonNode) => ThrowHelper.ThrowNotSupportedException_CollectionIsReadOnly();
 
             public void Clear() => ThrowHelper.ThrowNotSupportedException_CollectionIsReadOnly();
 
-            public bool Contains(T? jsonNode) => _parent.ContainsValue(jsonNode);
+            public bool Contains(T jsonNode) => _parent.ContainsValue(jsonNode);
 
-            public void CopyTo(T?[] nodeArray, int index)
+            public void CopyTo(T[] nodeArray, int index)
             {
                 if (index < 0)
                 {
                     ThrowHelper.ThrowArgumentOutOfRangeException_ArrayIndexNegative(nameof(index));
                 }
 
-                foreach (KeyValuePair<string, T?> item in _parent)
+                foreach (KeyValuePair<string, T> item in _parent)
                 {
                     if (index >= nodeArray.Length)
                     {
@@ -60,15 +60,15 @@ public void CopyTo(T?[] nodeArray, int index)
                 }
             }
 
-            public IEnumerator<T?> GetEnumerator()
+            public IEnumerator<T> GetEnumerator()
             {
-                foreach (KeyValuePair<string, T?> item in _parent)
+                foreach (KeyValuePair<string, T> item in _parent)
                 {
                     yield return item.Value;
                 }
             }
 
-            bool ICollection<T?>.Remove(T? node) => throw ThrowHelper.GetNotSupportedException_CollectionIsReadOnly();
+            bool ICollection<T>.Remove(T node) => throw ThrowHelper.GetNotSupportedException_CollectionIsReadOnly();
         }
     }
 }