Make JSON support required properties

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

@@ -659,4 +659,13 @@
   <data name="JsonPolymorphismOptionsAssociatedWithDifferentJsonTypeInfo" xml:space="preserve">
     <value>Parameter already associated with a different JsonTypeInfo instance.</value>
   </data>
+  <data name="JsonPropertyRequiredAndNotDeserializable" xml:space="preserve">
+    <value>JsonPropertyInfo '{0}' defined in type '{1}' is marked required but does not specify a setter.</value>
+  </data>
+  <data name="JsonPropertyRequiredAndExtensionData" xml:space="preserve">
+    <value>JsonPropertyInfo '{0}' defined in type '{1}' is marked both as required and as an extension data property. This combination is not supported.</value>
+  </data>
+  <data name="JsonRequiredPropertiesMissing" xml:space="preserve">
+    <value>JSON deserialization for type '{0}' was missing required properties, including the following: {1}</value>
+  </data>
 </root>

src/libraries/System.Text.Json/src/System/ReflectionExtensions.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.Diagnostics.CodeAnalysis;
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Runtime.ExceptionServices;
@@ -42,6 +43,39 @@ public static bool IsInSubtypeRelationshipWith(this Type type, Type other) =>
         private static bool HasJsonConstructorAttribute(ConstructorInfo constructorInfo)
             => constructorInfo.GetCustomAttribute<JsonConstructorAttribute>() != null;
 
+        public static bool HasRequiredMemberAttribute(this ICustomAttributeProvider memberInfo)
+        {
+#if NET7_0_OR_GREATER
+            return memberInfo.IsDefined(typeof(RequiredMemberAttribute), inherit: true);
+#else
+            return memberInfo.HasCustomAttributeWithName("System.Runtime.CompilerServices.RequiredMemberAttribute", inherit: true);
+#endif
+        }
+
+        public static bool HasSetsRequiredMembersAttribute(this ICustomAttributeProvider memberInfo)
+        {
+#if NET7_0_OR_GREATER
+            return memberInfo.IsDefined(typeof(SetsRequiredMembersAttribute), inherit: true);
+#else
+            return memberInfo.HasCustomAttributeWithName("System.Diagnostics.CodeAnalysis.SetsRequiredMembersAttribute", inherit: true);
+#endif
+        }
+
+#if !NET7_0_OR_GREATER
+        private static bool HasCustomAttributeWithName(this ICustomAttributeProvider memberInfo, string fullName, bool inherit)
+        {
+            foreach (object attribute in memberInfo.GetCustomAttributes(inherit))
+            {
+                if (attribute.GetType().FullName == fullName)
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+#endif
+
         public static TAttribute? GetUniqueCustomAttribute<TAttribute>(this MemberInfo memberInfo, bool inherit)
             where TAttribute : Attribute
         {

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

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Buffers;
+using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Runtime.CompilerServices;
@@ -147,5 +148,19 @@ public static void ValidateInt32MaxArrayLength(uint length)
                 ThrowHelper.ThrowOutOfMemoryException(length);
             }
         }
+
+        public static bool AllBitsEqual(this BitArray bitArray, bool value)
+        {
+            // Optimize this when https://github.com/dotnet/runtime/issues/72999 is fixed
+            for (int i = 0; i < bitArray.Count; i++)
+            {
+                if (bitArray[i] != value)
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
     }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Object/ObjectDefaultConverter.cs

@@ -39,6 +39,7 @@ internal override bool OnTryRead(ref Utf8JsonReader reader, Type typeToConvert,
                 obj = jsonTypeInfo.CreateObject()!;
 
                 jsonTypeInfo.OnDeserializing?.Invoke(obj);
+                state.Current.InitializeRequiredPropertiesValidationState(jsonTypeInfo);
 
                 // Process all properties.
                 while (true)
@@ -143,6 +144,7 @@ internal override bool OnTryRead(ref Utf8JsonReader reader, Type typeToConvert,
 
                     state.Current.ReturnValue = obj;
                     state.Current.ObjectState = StackFrameObjectState.CreatedObject;
+                    state.Current.InitializeRequiredPropertiesValidationState(jsonTypeInfo);
                 }
                 else
                 {
@@ -250,6 +252,7 @@ internal override bool OnTryRead(ref Utf8JsonReader reader, Type typeToConvert,
             }
 
             jsonTypeInfo.OnDeserialized?.Invoke(obj);
+            state.Current.ValidateAllRequiredPropertiesAreRead(jsonTypeInfo);
 
             // Unbox
             Debug.Assert(obj != null);

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Object/ObjectWithParameterizedConstructorConverter.Large.cs

@@ -24,6 +24,9 @@ protected sealed override bool ReadAndCacheConstructorArgument(ref ReadStack sta
             if (success && !(arg == null && jsonParameterInfo.IgnoreNullTokensOnRead))
             {
                 ((object[])state.Current.CtorArgumentState!.Arguments)[jsonParameterInfo.ClrInfo.Position] = arg!;
+
+                // if this is required property IgnoreNullTokensOnRead will always be false because we don't allow for both to be true
+                state.Current.MarkRequiredPropertyAsRead(jsonParameterInfo.MatchingProperty);
             }
 
             return success;

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Object/ObjectWithParameterizedConstructorConverter.Small.cs

@@ -71,6 +71,11 @@ private static bool TryRead<TArg>(
                 ? (TArg?)info.DefaultValue! // Use default value specified on parameter, if any.
                 : value!;
 
+            if (success)
+            {
+                state.Current.MarkRequiredPropertyAsRead(jsonParameterInfo.MatchingProperty);
+            }
+
             return success;
         }
 

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Object/ObjectWithParameterizedConstructorConverter.cs

@@ -184,7 +184,15 @@ internal sealed override bool OnTryRead(ref Utf8JsonReader reader, Type typeToCo
 
                         if (dataExtKey == null)
                         {
-                            jsonPropertyInfo.SetExtensionDictionaryAsObject(obj, propValue);
+                            Debug.Assert(jsonPropertyInfo.Set != null);
+
+                            if (propValue is not null || !jsonPropertyInfo.IgnoreNullTokensOnRead || default(T) is not null)
+                            {
+                                jsonPropertyInfo.Set(obj, propValue);
+
+                                // if this is required property IgnoreNullTokensOnRead will always be false because we don't allow for both to be true
+                                state.Current.MarkRequiredPropertyAsRead(jsonPropertyInfo);
+                            }
                         }
                         else
                         {
@@ -211,6 +219,7 @@ internal sealed override bool OnTryRead(ref Utf8JsonReader reader, Type typeToCo
             }
 
             jsonTypeInfo.OnDeserialized?.Invoke(obj);
+            state.Current.ValidateAllRequiredPropertiesAreRead(jsonTypeInfo);
 
             // Unbox
             Debug.Assert(obj != null);
@@ -272,6 +281,7 @@ private void ReadConstructorArguments(ref ReadStack state, ref Utf8JsonReader re
                         continue;
                     }
 
+                    Debug.Assert(jsonParameterInfo.MatchingProperty != null);
                     ReadAndCacheConstructorArgument(ref state, ref reader, jsonParameterInfo);
 
                     state.Current.EndConstructorParameter();
@@ -532,6 +542,8 @@ private void BeginRead(ref ReadStack state, ref Utf8JsonReader reader, JsonSeria
                 ThrowHelper.ThrowInvalidOperationException_ConstructorParameterIncompleteBinding(TypeToConvert);
             }
 
+            state.Current.InitializeRequiredPropertiesValidationState(jsonTypeInfo);
+
             // Set current JsonPropertyInfo to null to avoid conflicts on push.
             state.Current.JsonPropertyInfo = null;
 

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializer.Read.HandlePropertyName.cs

@@ -139,7 +139,8 @@ internal static void CreateExtensionDataProperty(
                 }
 
                 extensionData = createObjectForExtensionDataProp();
-                jsonPropertyInfo.SetExtensionDictionaryAsObject(obj, extensionData);
+                Debug.Assert(jsonPropertyInfo.Set != null);
+                jsonPropertyInfo.Set(obj, extensionData);
             }
 
             // We don't add the value to the dictionary here because we need to support the read-ahead functionality for Streams.

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonParameterInfo.cs

@@ -53,8 +53,11 @@ public JsonTypeInfo JsonTypeInfo
 
         public bool ShouldDeserialize { get; private set; }
 
+        public JsonPropertyInfo MatchingProperty { get; private set; } = null!;
+
         public virtual void Initialize(JsonParameterInfoValues parameterInfo, JsonPropertyInfo matchingProperty, JsonSerializerOptions options)
         {
+            MatchingProperty = matchingProperty;
             ClrInfo = parameterInfo;
             Options = options;
             ShouldDeserialize = true;

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonPropertyInfo.cs

@@ -203,6 +203,18 @@ public bool IsExtensionData
 
         private bool _isExtensionDataProperty;
 
+        internal bool IsRequired
+        {
+            get => _isRequired;
+            set
+            {
+                VerifyMutable();
+                _isRequired = value;
+            }
+        }
+
+        private bool _isRequired;
+
         internal JsonPropertyInfo(Type declaringType, Type propertyType, JsonTypeInfo? declaringTypeInfo, JsonSerializerOptions options)
         {
             Debug.Assert(declaringTypeInfo is null || declaringTypeInfo.Type == declaringType);
@@ -279,6 +291,21 @@ internal void Configure()
                 DetermineIgnoreCondition();
                 DetermineSerializationCapabilities();
             }
+
+            if (IsRequired)
+            {
+                if (!CanDeserialize)
+                {
+                    ThrowHelper.ThrowInvalidOperationException_JsonPropertyRequiredAndNotDeserializable(this);
+                }
+
+                if (IsExtensionData)
+                {
+                    ThrowHelper.ThrowInvalidOperationException_JsonPropertyRequiredAndExtensionData(this);
+                }
+
+                Debug.Assert(!IgnoreNullTokensOnRead);
+            }
         }
 
         private protected abstract void DetermineEffectiveConverter(JsonTypeInfo jsonTypeInfo);
@@ -341,7 +368,7 @@ private void DetermineIgnoreCondition()
                 Debug.Assert(Options.DefaultIgnoreCondition == JsonIgnoreCondition.Never);
                 if (PropertyTypeCanBeNull)
                 {
-                    IgnoreNullTokensOnRead = !_isUserSpecifiedSetter;
+                    IgnoreNullTokensOnRead = !_isUserSpecifiedSetter && !IsRequired;
                     IgnoreDefaultValuesOnWrite = ShouldSerialize is null;
                 }
             }
@@ -477,6 +504,14 @@ private bool NumberHandingIsApplicable()
                 potentialNumberType == JsonTypeInfo.ObjectType;
         }
 
+        private void DetermineIsRequired(MemberInfo memberInfo, bool shouldCheckForRequiredKeyword)
+        {
+            if (shouldCheckForRequiredKeyword && memberInfo.HasRequiredMemberAttribute())
+            {
+                IsRequired = true;
+            }
+        }
+
         internal abstract bool GetMemberAndWriteJson(object obj, ref WriteStack state, Utf8JsonWriter writer);
         internal abstract bool GetMemberAndWriteJsonExtensionData(object obj, ref WriteStack state, Utf8JsonWriter writer);
 
@@ -504,7 +539,7 @@ internal string GetDebugInfo(int indent = 0)
         internal bool HasGetter => _untypedGet is not null;
         internal bool HasSetter => _untypedSet is not null;
 
-        internal void InitializeUsingMemberReflection(MemberInfo memberInfo, JsonConverter? customConverter, JsonIgnoreCondition? ignoreCondition)
+        internal void InitializeUsingMemberReflection(MemberInfo memberInfo, JsonConverter? customConverter, JsonIgnoreCondition? ignoreCondition, bool shouldCheckForRequiredKeyword)
         {
             Debug.Assert(AttributeProvider == null);
 
@@ -531,6 +566,7 @@ internal void InitializeUsingMemberReflection(MemberInfo memberInfo, JsonConvert
             CustomConverter = customConverter;
             DeterminePoliciesFromMember(memberInfo);
             DeterminePropertyNameFromMember(memberInfo);
+            DetermineIsRequired(memberInfo, shouldCheckForRequiredKeyword);
 
             if (ignoreCondition != JsonIgnoreCondition.Always)
             {
@@ -760,8 +796,6 @@ internal JsonTypeInfo JsonTypeInfo
             }
         }
 
-        internal abstract void SetExtensionDictionaryAsObject(object obj, object? extensionDict);
-
         internal bool IsIgnored => _ignoreCondition == JsonIgnoreCondition.Always;
 
         /// <summary>
@@ -823,6 +857,29 @@ public JsonNumberHandling? NumberHandling
         /// </summary>
         internal abstract object? DefaultValue { get; }
 
+        /// <summary>
+        /// Required property index on the list of JsonTypeInfo properties.
+        /// It is used as a unique identifier for required properties.
+        /// It is set just before property is configured and does not change afterward.
+        /// It is not equivalent to index on the properties list
+        /// </summary>
+        internal int RequiredPropertyIndex
+        {
+            get
+            {
+                Debug.Assert(_isConfigured);
+                Debug.Assert(IsRequired);
+                return _index;
+            }
+            set
+            {
+                Debug.Assert(!_isConfigured);
+                _index = value;
+            }
+        }
+
+        private int _index;
+
         [DebuggerBrowsable(DebuggerBrowsableState.Never)]
         private string DebuggerDisplay => $"PropertyType = {PropertyType}, Name = {Name}, DeclaringType = {DeclaringType}";
     }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonPropertyInfoOfT.cs

@@ -342,6 +342,7 @@ internal override bool ReadJsonAndSetMember(object obj, ref ReadStack state, ref
                 }
 
                 success = true;
+                state.Current.MarkRequiredPropertyAsRead(this);
             }
             else if (TypedEffectiveConverter.CanUseDirectReadOrWrite && state.Current.NumberHandling == null)
             {
@@ -356,6 +357,7 @@ internal override bool ReadJsonAndSetMember(object obj, ref ReadStack state, ref
                 }
 
                 success = true;
+                state.Current.MarkRequiredPropertyAsRead(this);
             }
             else
             {
@@ -366,6 +368,7 @@ internal override bool ReadJsonAndSetMember(object obj, ref ReadStack state, ref
                     if (success)
                     {
                         Set!(obj, value!);
+                        state.Current.MarkRequiredPropertyAsRead(this);
                     }
                 }
             }
@@ -408,13 +411,6 @@ internal override bool ReadJsonAsObject(ref ReadStack state, ref Utf8JsonReader
             return success;
         }
 
-        internal override void SetExtensionDictionaryAsObject(object obj, object? extensionDict)
-        {
-            Debug.Assert(HasSetter);
-            T typedValue = (T)extensionDict!;
-            Set!(obj, typedValue);
-        }
-
         private protected override void ConfigureIgnoreCondition(JsonIgnoreCondition? ignoreCondition)
         {
             switch (ignoreCondition)

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonTypeInfo.cs

@@ -26,6 +26,11 @@ public abstract partial class JsonTypeInfo
 
         private JsonPropertyInfoList? _properties;
 
+        /// <summary>
+        /// Indices of required properties.
+        /// </summary>
+        internal int NumberOfRequiredProperties { get; private set; }
+
         private Action<object>? _onSerializing;
         private Action<object>? _onSerialized;
         private Action<object>? _onDeserializing;
@@ -878,13 +883,21 @@ internal void InitializePropertyCache()
                 ExtensionDataProperty.EnsureConfigured();
             }
 
+            int numberOfRequiredProperties = 0;
             foreach (KeyValuePair<string, JsonPropertyInfo> jsonPropertyInfoKv in PropertyCache.List)
             {
                 JsonPropertyInfo jsonPropertyInfo = jsonPropertyInfoKv.Value;
 
+                if (jsonPropertyInfo.IsRequired)
+                {
+                    jsonPropertyInfo.RequiredPropertyIndex = numberOfRequiredProperties++;
+                }
+
                 jsonPropertyInfo.EnsureChildOf(this);
                 jsonPropertyInfo.EnsureConfigured();
             }
+
+            NumberOfRequiredProperties = numberOfRequiredProperties;
         }
 
         internal void InitializeConstructorParameters(JsonParameterInfoValues[] jsonParameters, bool sourceGenMode = false)