Implement JsonSerializerOptions.RespectRequiredConstructorParameters

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

@@ -120,6 +120,11 @@ public JsonSourceGenerationOptionsAttribute(JsonSerializerDefaults defaults)
  /// </summary>
  public bool RespectNullableAnnotations { get; set; }
 
+ /// <summary>
+ /// Specifies the default value of <see cref="JsonSerializerOptions.RespectRequiredConstructorParameters"/> when set.
+ /// </summary>
+ public bool RespectRequiredConstructorParameters { get; set; }
+
  /// <summary>
  /// Specifies the default value of <see cref="JsonSerializerOptions.UnknownTypeHandling"/> when set.
  /// </summary>

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

@@ -1207,6 +1207,9 @@ private static void GetLogicForDefaultSerializerOptionsInit(SourceGenerationOpti
  if (optionsSpec.RespectNullableAnnotations is bool respectNullableAnnotations)
  writer.WriteLine($"RespectNullableAnnotations = {FormatBoolLiteral(respectNullableAnnotations)},");
 
+ if (optionsSpec.RespectRequiredConstructorParameters is bool respectRequiredConstructorParameters)
+ writer.WriteLine($"RespectRequiredConstructorParameters = {FormatBoolLiteral(respectRequiredConstructorParameters)},");
+
  if (optionsSpec.IgnoreReadOnlyFields is bool ignoreReadOnlyFields)
  writer.WriteLine($"IgnoreReadOnlyFields = {FormatBoolLiteral(ignoreReadOnlyFields)},");
 

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

@@ -270,6 +270,7 @@ private SourceGenerationOptionsSpec ParseJsonSourceGenerationOptionsAttribute(IN
  JsonKnownNamingPolicy? dictionaryKeyPolicy = null;
  bool? respectNullableAnnotations = null;
  bool? ignoreReadOnlyFields = null;
+ bool? respectRequiredConstructorParameters = null;
  bool? ignoreReadOnlyProperties = null;
  bool? includeFields = null;
  int? maxDepth = null;
@@ -334,6 +335,10 @@ private SourceGenerationOptionsSpec ParseJsonSourceGenerationOptionsAttribute(IN
  respectNullableAnnotations = (bool)namedArg.Value.Value!;
  break;
 
+ case nameof(JsonSourceGenerationOptionsAttribute.RespectRequiredConstructorParameters):
+ respectRequiredConstructorParameters = (bool)namedArg.Value.Value!;
+ break;
+
  case nameof(JsonSourceGenerationOptionsAttribute.IgnoreReadOnlyFields):
  ignoreReadOnlyFields = (bool)namedArg.Value.Value!;
  break;
@@ -418,6 +423,7 @@ private SourceGenerationOptionsSpec ParseJsonSourceGenerationOptionsAttribute(IN
  DefaultIgnoreCondition = defaultIgnoreCondition,
  DictionaryKeyPolicy = dictionaryKeyPolicy,
  RespectNullableAnnotations = respectNullableAnnotations,
+ RespectRequiredConstructorParameters = respectRequiredConstructorParameters,
  IgnoreReadOnlyFields = ignoreReadOnlyFields,
  IgnoreReadOnlyProperties = ignoreReadOnlyProperties,
  IncludeFields = includeFields,

src/libraries/System.Text.Json/gen/Model/SourceGenerationOptionsSpec.cs

@@ -30,6 +30,8 @@ public sealed record SourceGenerationOptionsSpec
 
  public required bool? RespectNullableAnnotations { get; init; }
 
+ public required bool? RespectRequiredConstructorParameters { get; init; }
+
  public required bool? IgnoreReadOnlyFields { get; init; }
 
  public required bool? IgnoreReadOnlyProperties { get; init; }

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

@@ -402,6 +402,7 @@ public JsonSerializerOptions(System.Text.Json.JsonSerializerOptions options) { }
  public System.Text.Json.JsonCommentHandling ReadCommentHandling { get { throw null; } set { } }
  public System.Text.Json.Serialization.ReferenceHandler? ReferenceHandler { get { throw null; } set { } }
  public bool RespectNullableAnnotations { get { throw null; } set { } }
+ public bool RespectRequiredConstructorParameters { get { throw null; } set { } }
  public System.Text.Json.Serialization.Metadata.IJsonTypeInfoResolver? TypeInfoResolver { get { throw null; } set { } }
  public System.Collections.Generic.IList<System.Text.Json.Serialization.Metadata.IJsonTypeInfoResolver> TypeInfoResolverChain { get { throw null; } }
  public System.Text.Json.Serialization.JsonUnknownTypeHandling UnknownTypeHandling { get { throw null; } set { } }
@@ -1093,6 +1094,7 @@ public JsonSourceGenerationOptionsAttribute(System.Text.Json.JsonSerializerDefau
  public System.Text.Json.Serialization.JsonKnownNamingPolicy PropertyNamingPolicy { get { throw null; } set { } }
  public System.Text.Json.JsonCommentHandling ReadCommentHandling { get { throw null; } set { } }
  public bool RespectNullableAnnotations { get { throw null; } set { } }
+ public bool RespectRequiredConstructorParameters { get { throw null; } set { } }
  public System.Text.Json.Serialization.JsonUnknownTypeHandling UnknownTypeHandling { get { throw null; } set { } }
  public System.Text.Json.Serialization.JsonUnmappedMemberHandling UnmappedMemberHandling { get { throw null; } set { } }
  public bool UseStringEnumConverter { get { throw null; } set { } }

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

@@ -693,7 +693,7 @@
  <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>
+ <value>JSON deserialization for type '{0}' was missing required properties including: {1}.</value>
  </data>
  <data name="ObjectCreationHandlingPopulateNotSupportedByConverter" xml:space="preserve">
  <value>Property '{0}' on type '{1}' is marked with JsonObjectCreationHandling.Populate but it doesn't support populating. This can be either because the property type is immutable or it could use a custom converter.</value>

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

@@ -16,5 +16,11 @@ internal static class AppContextSwitchHelper
  switchName: "System.Text.Json.Serialization.RespectNullableAnnotationsDefault",
  isEnabled: out bool value)
  ? value : false;
+
+ public static bool RespectRequiredConstructorParametersDefault { get; } =
+ AppContext.TryGetSwitch(
+ switchName: "System.Text.Json.Serialization.RespectRequiredConstructorParametersDefault",
+ isEnabled: out bool value)
+ ? value : false;
  }
 }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.Caching.cs

@@ -508,6 +508,7 @@ public bool Equals(JsonSerializerOptions? left, JsonSerializerOptions? right)
  left._allowOutOfOrderMetadataProperties == right._allowOutOfOrderMetadataProperties &&
  left._allowTrailingCommas == right._allowTrailingCommas &&
  left._respectNullableAnnotations == right._respectNullableAnnotations &&
+ left._respectRequiredConstructorParameters == right._respectRequiredConstructorParameters &&
  left._ignoreNullValues == right._ignoreNullValues &&
  left._ignoreReadOnlyProperties == right._ignoreReadOnlyProperties &&
  left._ignoreReadonlyFields == right._ignoreReadonlyFields &&
@@ -567,6 +568,7 @@ public int GetHashCode(JsonSerializerOptions options)
  AddHashCode(ref hc, options._allowOutOfOrderMetadataProperties);
  AddHashCode(ref hc, options._allowTrailingCommas);
  AddHashCode(ref hc, options._respectNullableAnnotations);
+ AddHashCode(ref hc, options._respectRequiredConstructorParameters);
  AddHashCode(ref hc, options._ignoreNullValues);
  AddHashCode(ref hc, options._ignoreReadOnlyProperties);
  AddHashCode(ref hc, options._ignoreReadonlyFields);

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.cs

@@ -87,6 +87,7 @@ public static JsonSerializerOptions Web
  private bool _allowOutOfOrderMetadataProperties;
  private bool _allowTrailingCommas;
  private bool _respectNullableAnnotations = AppContextSwitchHelper.RespectNullableAnnotationsDefault;
+ private bool _respectRequiredConstructorParameters = AppContextSwitchHelper.RespectRequiredConstructorParametersDefault;
  private bool _ignoreNullValues;
  private bool _ignoreReadOnlyProperties;
  private bool _ignoreReadonlyFields;
@@ -141,6 +142,7 @@ public JsonSerializerOptions(JsonSerializerOptions options)
  _allowOutOfOrderMetadataProperties = options._allowOutOfOrderMetadataProperties;
  _allowTrailingCommas = options._allowTrailingCommas;
  _respectNullableAnnotations = options._respectNullableAnnotations;
+ _respectRequiredConstructorParameters = options._respectRequiredConstructorParameters;
  _ignoreNullValues = options._ignoreNullValues;
  _ignoreReadOnlyProperties = options._ignoreReadOnlyProperties;
  _ignoreReadonlyFields = options._ignoreReadonlyFields;
@@ -797,6 +799,9 @@ public string NewLine
  /// Due to restrictions in how nullable reference types are represented at run time,
  /// this setting only governs nullability annotations of non-generic properties and fields.
  /// It cannot be used to enforce nullability annotations of root-level types or generic parameters.
+ ///
+ /// The default setting for this property can be toggled application-wide using the
+ /// "System.Text.Json.Serialization.RespectNullableAnnotationsDefault" feature switch.
  /// </remarks>
  public bool RespectNullableAnnotations
  {
@@ -808,6 +813,29 @@ public bool RespectNullableAnnotations
  }
  }
 
+ /// <summary>
+ /// Gets or sets a value that indicates whether non-optional constructor parameters should be specified during deserialization.
+ /// </summary>
+ /// <exception cref="InvalidOperationException">
+ /// Thrown if this property is set after serialization or deserialization has occurred.
+ /// </exception>
+ /// <remarks>
+ /// For historical reasons constructor-based deserialization treats all constructor parameters as optional by default.
+ /// This flag allows users to toggle that behavior as necessary for each <see cref="JsonSerializerOptions"/> instance.
+ ///
+ /// The default setting for this property can be toggled application-wide using the
+ /// "System.Text.Json.Serialization.RespectRequiredConstructorParametersDefault" feature switch.
+ /// </remarks>
+ public bool RespectRequiredConstructorParameters
+ {
+ get => _respectRequiredConstructorParameters;
+ set
+ {
+ VerifyMutable();
+ _respectRequiredConstructorParameters = value;
+ }
+ }
+
  /// <summary>
  /// Returns true if options uses compatible built-in resolvers or a combination of compatible built-in resolvers.
  /// </summary>

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

@@ -123,5 +123,9 @@ public ICustomAttributeProvider? AttributeProvider
  internal JsonNumberHandling? NumberHandling => MatchingProperty.EffectiveNumberHandling;
  internal JsonTypeInfo JsonTypeInfo => MatchingProperty.JsonTypeInfo;
  internal bool ShouldDeserialize => !MatchingProperty.IsIgnored;
+ internal bool IsRequiredParameter =>
+ Options.RespectRequiredConstructorParameters &&
+ !HasDefaultValue &&
+ !IsMemberInitializer;
  }
 }

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

@@ -356,7 +356,7 @@ public bool IsRequired
  }
  }
 
- private bool _isRequired;
+ private protected bool _isRequired;
 
  /// <summary>
  /// Gets the constructor parameter associated with the current property.
@@ -448,7 +448,7 @@ internal void Configure()
 
  if (IsRequired)
  {
- if (!CanDeserialize)
+ if (!CanDeserialize && AssociatedParameter?.IsRequiredParameter != true)
  {
  ThrowHelper.ThrowInvalidOperationException_JsonPropertyRequiredAndNotDeserializable(this);
  }

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

@@ -120,6 +120,8 @@ internal override void AddJsonParameterInfo(JsonParameterInfoValues parameterInf
  AssociatedParameter = new JsonParameterInfo<T>(parameterInfoValues, this);
  // Overwrite the nullability annotation of property setter with the parameter.
  _isSetNullable = parameterInfoValues.IsNullable;
+ // If the property has been associated with a non-optional parameter, mark it as required.
+ _isRequired |= AssociatedParameter.IsRequiredParameter;
  }
 
  internal new JsonConverter<T> EffectiveConverter

src/libraries/System.Text.Json/src/System/Text/Json/ThrowHelper.Serialization.cs

@@ -296,7 +296,7 @@ public static void ThrowJsonException_JsonRequiredPropertyMissing(JsonTypeInfo p
  Debug.Assert(parent.PropertyCache != null);
 
  // Soft cut-off length - once message becomes longer than that we won't be adding more elements
- const int CutOffLength = 50;
+ const int CutOffLength = 60;
 
  foreach (KeyValuePair<string, JsonPropertyInfo> kvp in parent.PropertyCache.List)
  {
@@ -313,7 +313,9 @@ public static void ThrowJsonException_JsonRequiredPropertyMissing(JsonTypeInfo p
  listOfMissingPropertiesBuilder.Append(' ');
  }
 
+ listOfMissingPropertiesBuilder.Append('\'');
  listOfMissingPropertiesBuilder.Append(property.Name);
+ listOfMissingPropertiesBuilder.Append('\'');
  first = false;
 
  if (listOfMissingPropertiesBuilder.Length >= CutOffLength)

src/libraries/System.Text.Json/tests/Common/ConstructorTests/ConstructorTests.ParameterMatching.cs

@@ -12,6 +12,8 @@ namespace System.Text.Json.Serialization.Tests
 {
  public abstract partial class ConstructorTests : SerializerTests
  {
+ private static readonly JsonSerializerOptions s_respectRequiredParamsOptions = new() { RespectRequiredConstructorParameters = true };
+
  public ConstructorTests(JsonSerializerWrapper stringSerializer)
  : base(stringSerializer)
  {
@@ -1636,5 +1638,35 @@ public class CustomCtorParameterConverter : JsonConverter<string>
  public override void Write(Utf8JsonWriter writer, string value, JsonSerializerOptions options)
  => writer.WriteStringValue(value);
  }
+
+ [Fact]
+ public async Task RespectRequiredConstructorParameters_RequiredParameterMissing_ThrowsJsonException()
+ {
+ string json = """{"X":1,"Z":3}""";
+ JsonException ex = await Assert.ThrowsAsync<JsonException>(() => Serializer.DeserializeWrapper<Point_3D>(json, s_respectRequiredParamsOptions));
+ Assert.DoesNotContain("'X'", ex.Message);
+ Assert.Contains("'Y'", ex.Message);
+ Assert.DoesNotContain("'Z'", ex.Message);
+ }
+
+ [Fact]
+ public async Task RespectRequiredConstructorParameters_OptionalParameterMissing_Succeeds()
+ {
+ string json = """{"X":1,"Y":2}""";
+ Point_3D result = await Serializer.DeserializeWrapper<Point_3D>(json, s_respectRequiredParamsOptions);
+ Assert.Equal(1, result.X);
+ Assert.Equal(2, result.Y);
+ Assert.Equal(50, result.Z);
+ }
+
+ [Fact]
+ public async Task RespectRequiredConstructorParameters_NoParameterMissing_Succeeds()
+ {
+ string json = """{"X":1,"Y":2,"Z":3}""";
+ Point_3D result = await Serializer.DeserializeWrapper<Point_3D>(json, s_respectRequiredParamsOptions);
+ Assert.Equal(1, result.X);
+ Assert.Equal(2, result.Y);
+ Assert.Equal(3, result.Z);
+ }
  }
 }

src/libraries/System.Text.Json/tests/Common/MetadataTests.cs

@@ -271,6 +271,39 @@ public void JsonTypeInfo_ElementType_ReturnsExpectedValue(Type type, Type? expec
  Assert.Equal(expectedKeyType, typeInfo.ElementType);
  }
 
+ [Theory]
+ [InlineData(typeof(ClassWithParameterizedCtor))]
+ [InlineData(typeof(StructWithParameterizedCtor))]
+ [InlineData(typeof(ClassWithRequiredAndOptionalConstructorParameters))]
+ public void RespectRequiredConstructorParameters_false_ReportsCorrespondingPropertiesAsNotRequired(Type type)
+ {
+ var options = new JsonSerializerOptions { RespectRequiredConstructorParameters = false };
+ JsonTypeInfo typeInfo = Serializer.GetTypeInfo(type, options);
+
+ Assert.NotEmpty(typeInfo.Properties);
+ Assert.All(typeInfo.Properties, property =>
+ {
+ Assert.False(property.IsRequired);
+ });
+ }
+
+ [Theory]
+ [InlineData(typeof(ClassWithParameterizedCtor))]
+ [InlineData(typeof(StructWithParameterizedCtor))]
+ [InlineData(typeof(ClassWithRequiredAndOptionalConstructorParameters))]
+ public void RespectRequiredConstructorParameters_true_ReportsCorrespondingPropertiesAsRequired(Type type)
+ {
+ var options = new JsonSerializerOptions { RespectRequiredConstructorParameters = true };
+ JsonTypeInfo typeInfo = Serializer.GetTypeInfo(type, options);
+
+ Assert.NotEmpty(typeInfo.Properties);
+ Assert.All(typeInfo.Properties, property =>
+ {
+ bool isRequiredParam = property.AssociatedParameter is { HasDefaultValue: false, IsMemberInitializer: false };
+ Assert.Equal(isRequiredParam, property.IsRequired);
+ });
+ }
+
  private static object? GetDefaultValue(ParameterInfo parameterInfo)
  {
  Type parameterType = parameterInfo.ParameterType;
@@ -506,6 +539,18 @@ public sealed class CustomConverter : JsonConverter<DerivedDictionaryWithCustomC
  public override void Write(Utf8JsonWriter writer, DerivedDictionaryWithCustomConverter value, JsonSerializerOptions options) => throw new NotImplementedException();
  }
  }
+
+ internal class ClassWithRequiredAndOptionalConstructorParameters
+ {
+ [JsonConstructor]
+ public ClassWithRequiredAndOptionalConstructorParameters(string? x, string? y = null)
+ {
+ X = x;
+ Y = y;
+ }
+ public string? X { get; }
+ public string? Y { get; }
+ }
  }
 
  internal class WeatherForecastWithPOCOs

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/Serialization/MetadataTests.cs

@@ -39,6 +39,7 @@ public partial class MetadataTests_SourceGen() : MetadataTests(new StringSeriali
  [JsonSerializable(typeof(ClassWithMultipleConstructors))]
  [JsonSerializable(typeof(DerivedClassWithShadowingProperties))]
  [JsonSerializable(typeof(IDerivedInterface))]
+ [JsonSerializable(typeof(ClassWithRequiredAndOptionalConstructorParameters))]
  partial class Context : JsonSerializerContext;
  }
 }

src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CacheTests.cs

@@ -374,6 +374,7 @@ public static void JsonSerializerOptions_EqualityComparer_ChangingAnySettingShou
  yield return (GetProp(nameof(JsonSerializerOptions.UnknownTypeHandling)), JsonUnknownTypeHandling.JsonNode);
  yield return (GetProp(nameof(JsonSerializerOptions.WriteIndented)), true);
  yield return (GetProp(nameof(JsonSerializerOptions.RespectNullableAnnotations)), !JsonSerializerOptions.Default.RespectNullableAnnotations);
+ yield return (GetProp(nameof(JsonSerializerOptions.RespectRequiredConstructorParameters)), !JsonSerializerOptions.Default.RespectRequiredConstructorParameters);
  yield return (GetProp(nameof(JsonSerializerOptions.IndentCharacter)), '\t');
  yield return (GetProp(nameof(JsonSerializerOptions.IndentSize)), 1);
  yield return (GetProp(nameof(JsonSerializerOptions.ReferenceHandler)), ReferenceHandler.Preserve);