diff --git a/eng/MSBuild/LegacySupport.props b/eng/MSBuild/LegacySupport.props
index 9e83541b0d8..1f0f22c7aa8 100644
--- a/eng/MSBuild/LegacySupport.props
+++ b/eng/MSBuild/LegacySupport.props
@@ -74,4 +74,8 @@
+
+
+
+
diff --git a/src/LegacySupport/NullabilityInfoContext/NullabilityInfo.cs b/src/LegacySupport/NullabilityInfoContext/NullabilityInfo.cs
new file mode 100644
index 00000000000..bd9b132cd0f
--- /dev/null
+++ b/src/LegacySupport/NullabilityInfoContext/NullabilityInfo.cs
@@ -0,0 +1,75 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#if !NET6_0_OR_GREATER
+using System.Diagnostics.CodeAnalysis;
+
+#pragma warning disable SA1623 // Property summary documentation should match accessors
+
+namespace System.Reflection
+{
+ ///
+ /// A class that represents nullability info.
+ ///
+ [ExcludeFromCodeCoverage]
+ internal sealed class NullabilityInfo
+ {
+ internal NullabilityInfo(Type type, NullabilityState readState, NullabilityState writeState,
+ NullabilityInfo? elementType, NullabilityInfo[] typeArguments)
+ {
+ Type = type;
+ ReadState = readState;
+ WriteState = writeState;
+ ElementType = elementType;
+ GenericTypeArguments = typeArguments;
+ }
+
+ ///
+ /// The of the member or generic parameter
+ /// to which this NullabilityInfo belongs.
+ ///
+ public Type Type { get; }
+
+ ///
+ /// The nullability read state of the member.
+ ///
+ public NullabilityState ReadState { get; internal set; }
+
+ ///
+ /// The nullability write state of the member.
+ ///
+ public NullabilityState WriteState { get; internal set; }
+
+ ///
+ /// If the member type is an array, gives the of the elements of the array, null otherwise.
+ ///
+ public NullabilityInfo? ElementType { get; }
+
+ ///
+ /// If the member type is a generic type, gives the array of for each type parameter.
+ ///
+ public NullabilityInfo[] GenericTypeArguments { get; }
+ }
+
+ ///
+ /// An enum that represents nullability state.
+ ///
+ internal enum NullabilityState
+ {
+ ///
+ /// Nullability context not enabled (oblivious).
+ ///
+ Unknown,
+
+ ///
+ /// Non nullable value or reference type.
+ ///
+ NotNull,
+
+ ///
+ /// Nullable value or reference type.
+ ///
+ Nullable,
+ }
+}
+#endif
diff --git a/src/LegacySupport/NullabilityInfoContext/NullabilityInfoContext.cs b/src/LegacySupport/NullabilityInfoContext/NullabilityInfoContext.cs
new file mode 100644
index 00000000000..33f13a56164
--- /dev/null
+++ b/src/LegacySupport/NullabilityInfoContext/NullabilityInfoContext.cs
@@ -0,0 +1,661 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#if !NET6_0_OR_GREATER
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+
+#pragma warning disable SA1204 // Static elements should appear before instance elements
+#pragma warning disable S109 // Magic numbers should not be used
+#pragma warning disable S1067 // Expressions should not be too complex
+#pragma warning disable S4136 // Method overloads should be grouped together
+#pragma warning disable SA1202 // Elements should be ordered by access
+#pragma warning disable IDE1006 // Naming Styles
+
+namespace System.Reflection
+{
+ ///
+ /// Provides APIs for populating nullability information/context from reflection members:
+ /// , , and .
+ ///
+ [ExcludeFromCodeCoverage]
+ internal sealed class NullabilityInfoContext
+ {
+ private const string CompilerServicesNameSpace = "System.Runtime.CompilerServices";
+ private readonly Dictionary _publicOnlyModules = new();
+ private readonly Dictionary _context = new();
+
+ [Flags]
+ private enum NotAnnotatedStatus
+ {
+ None = 0x0, // no restriction, all members annotated
+ Private = 0x1, // private members not annotated
+ Internal = 0x2, // internal members not annotated
+ }
+
+ private NullabilityState? GetNullableContext(MemberInfo? memberInfo)
+ {
+ while (memberInfo != null)
+ {
+ if (_context.TryGetValue(memberInfo, out NullabilityState state))
+ {
+ return state;
+ }
+
+ foreach (CustomAttributeData attribute in memberInfo.GetCustomAttributesData())
+ {
+ if (attribute.AttributeType.Name == "NullableContextAttribute" &&
+ attribute.AttributeType.Namespace == CompilerServicesNameSpace &&
+ attribute.ConstructorArguments.Count == 1)
+ {
+ state = TranslateByte(attribute.ConstructorArguments[0].Value);
+ _context.Add(memberInfo, state);
+ return state;
+ }
+ }
+
+ memberInfo = memberInfo.DeclaringType;
+ }
+
+ return null;
+ }
+
+ ///
+ /// Populates for the given .
+ /// If the nullablePublicOnly feature is set for an assembly, like it does in .NET SDK, the private and/or internal member's
+ /// nullability attributes are omitted, in this case the API will return NullabilityState.Unknown state.
+ ///
+ /// The parameter which nullability info gets populated.
+ /// If the parameterInfo parameter is null.
+ /// .
+ public NullabilityInfo Create(ParameterInfo parameterInfo)
+ {
+ IList attributes = parameterInfo.GetCustomAttributesData();
+ NullableAttributeStateParser parser = parameterInfo.Member is MethodBase method && IsPrivateOrInternalMethodAndAnnotationDisabled(method)
+ ? NullableAttributeStateParser.Unknown
+ : CreateParser(attributes);
+ NullabilityInfo nullability = GetNullabilityInfo(parameterInfo.Member, parameterInfo.ParameterType, parser);
+
+ if (nullability.ReadState != NullabilityState.Unknown)
+ {
+ CheckParameterMetadataType(parameterInfo, nullability);
+ }
+
+ CheckNullabilityAttributes(nullability, attributes);
+ return nullability;
+ }
+
+ private void CheckParameterMetadataType(ParameterInfo parameter, NullabilityInfo nullability)
+ {
+ ParameterInfo? metaParameter;
+ MemberInfo metaMember;
+
+ switch (parameter.Member)
+ {
+ case ConstructorInfo ctor:
+ var metaCtor = (ConstructorInfo)GetMemberMetadataDefinition(ctor);
+ metaMember = metaCtor;
+ metaParameter = GetMetaParameter(metaCtor, parameter);
+ break;
+
+ case MethodInfo method:
+ MethodInfo metaMethod = GetMethodMetadataDefinition(method);
+ metaMember = metaMethod;
+ metaParameter = string.IsNullOrEmpty(parameter.Name) ? metaMethod.ReturnParameter : GetMetaParameter(metaMethod, parameter);
+ break;
+
+ default:
+ return;
+ }
+
+ if (metaParameter != null)
+ {
+ CheckGenericParameters(nullability, metaMember, metaParameter.ParameterType, parameter.Member.ReflectedType);
+ }
+ }
+
+ private static ParameterInfo? GetMetaParameter(MethodBase metaMethod, ParameterInfo parameter)
+ {
+ var parameters = metaMethod.GetParameters();
+ for (int i = 0; i < parameters.Length; i++)
+ {
+ if (parameter.Position == i &&
+ parameter.Name == parameters[i].Name)
+ {
+ return parameters[i];
+ }
+ }
+
+ return null;
+ }
+
+ private static MethodInfo GetMethodMetadataDefinition(MethodInfo method)
+ {
+ if (method.IsGenericMethod && !method.IsGenericMethodDefinition)
+ {
+ method = method.GetGenericMethodDefinition();
+ }
+
+ return (MethodInfo)GetMemberMetadataDefinition(method);
+ }
+
+ private static void CheckNullabilityAttributes(NullabilityInfo nullability, IList attributes)
+ {
+ var codeAnalysisReadState = NullabilityState.Unknown;
+ var codeAnalysisWriteState = NullabilityState.Unknown;
+
+ foreach (CustomAttributeData attribute in attributes)
+ {
+ if (attribute.AttributeType.Namespace == "System.Diagnostics.CodeAnalysis")
+ {
+ if (attribute.AttributeType.Name == "NotNullAttribute")
+ {
+ codeAnalysisReadState = NullabilityState.NotNull;
+ }
+ else if ((attribute.AttributeType.Name == "MaybeNullAttribute" ||
+ attribute.AttributeType.Name == "MaybeNullWhenAttribute") &&
+ codeAnalysisReadState == NullabilityState.Unknown &&
+ !IsValueTypeOrValueTypeByRef(nullability.Type))
+ {
+ codeAnalysisReadState = NullabilityState.Nullable;
+ }
+ else if (attribute.AttributeType.Name == "DisallowNullAttribute")
+ {
+ codeAnalysisWriteState = NullabilityState.NotNull;
+ }
+ else if (attribute.AttributeType.Name == "AllowNullAttribute" &&
+ codeAnalysisWriteState == NullabilityState.Unknown &&
+ !IsValueTypeOrValueTypeByRef(nullability.Type))
+ {
+ codeAnalysisWriteState = NullabilityState.Nullable;
+ }
+ }
+ }
+
+ if (codeAnalysisReadState != NullabilityState.Unknown)
+ {
+ nullability.ReadState = codeAnalysisReadState;
+ }
+
+ if (codeAnalysisWriteState != NullabilityState.Unknown)
+ {
+ nullability.WriteState = codeAnalysisWriteState;
+ }
+ }
+
+ ///
+ /// Populates for the given .
+ /// If the nullablePublicOnly feature is set for an assembly, like it does in .NET SDK, the private and/or internal member's
+ /// nullability attributes are omitted, in this case the API will return NullabilityState.Unknown state.
+ ///
+ /// The parameter which nullability info gets populated.
+ /// If the propertyInfo parameter is null.
+ /// .
+ public NullabilityInfo Create(PropertyInfo propertyInfo)
+ {
+ MethodInfo? getter = propertyInfo.GetGetMethod(true);
+ MethodInfo? setter = propertyInfo.GetSetMethod(true);
+ bool annotationsDisabled = (getter == null || IsPrivateOrInternalMethodAndAnnotationDisabled(getter))
+ && (setter == null || IsPrivateOrInternalMethodAndAnnotationDisabled(setter));
+ NullableAttributeStateParser parser = annotationsDisabled ? NullableAttributeStateParser.Unknown : CreateParser(propertyInfo.GetCustomAttributesData());
+ NullabilityInfo nullability = GetNullabilityInfo(propertyInfo, propertyInfo.PropertyType, parser);
+
+ if (getter != null)
+ {
+ CheckNullabilityAttributes(nullability, getter.ReturnParameter.GetCustomAttributesData());
+ }
+ else
+ {
+ nullability.ReadState = NullabilityState.Unknown;
+ }
+
+ if (setter != null)
+ {
+ var setterParams = setter.GetParameters();
+ CheckNullabilityAttributes(nullability, setterParams[setterParams.Length - 1].GetCustomAttributesData());
+ }
+ else
+ {
+ nullability.WriteState = NullabilityState.Unknown;
+ }
+
+ return nullability;
+ }
+
+ private bool IsPrivateOrInternalMethodAndAnnotationDisabled(MethodBase method)
+ {
+ if ((method.IsPrivate || method.IsFamilyAndAssembly || method.IsAssembly) &&
+ IsPublicOnly(method.IsPrivate, method.IsFamilyAndAssembly, method.IsAssembly, method.Module))
+ {
+ return true;
+ }
+
+ return false;
+ }
+
+ ///
+ /// Populates for the given .
+ /// If the nullablePublicOnly feature is set for an assembly, like it does in .NET SDK, the private and/or internal member's
+ /// nullability attributes are omitted, in this case the API will return NullabilityState.Unknown state.
+ ///
+ /// The parameter which nullability info gets populated.
+ /// If the eventInfo parameter is null.
+ /// .
+ public NullabilityInfo Create(EventInfo eventInfo)
+ {
+ return GetNullabilityInfo(eventInfo, eventInfo.EventHandlerType!, CreateParser(eventInfo.GetCustomAttributesData()));
+ }
+
+ ///
+ /// Populates for the given
+ /// If the nullablePublicOnly feature is set for an assembly, like it does in .NET SDK, the private and/or internal member's
+ /// nullability attributes are omitted, in this case the API will return NullabilityState.Unknown state.
+ ///
+ /// The parameter which nullability info gets populated.
+ /// If the fieldInfo parameter is null.
+ /// .
+ public NullabilityInfo Create(FieldInfo fieldInfo)
+ {
+ IList attributes = fieldInfo.GetCustomAttributesData();
+ NullableAttributeStateParser parser = IsPrivateOrInternalFieldAndAnnotationDisabled(fieldInfo) ? NullableAttributeStateParser.Unknown : CreateParser(attributes);
+ NullabilityInfo nullability = GetNullabilityInfo(fieldInfo, fieldInfo.FieldType, parser);
+ CheckNullabilityAttributes(nullability, attributes);
+ return nullability;
+ }
+
+ private bool IsPrivateOrInternalFieldAndAnnotationDisabled(FieldInfo fieldInfo)
+ {
+ if ((fieldInfo.IsPrivate || fieldInfo.IsFamilyAndAssembly || fieldInfo.IsAssembly) &&
+ IsPublicOnly(fieldInfo.IsPrivate, fieldInfo.IsFamilyAndAssembly, fieldInfo.IsAssembly, fieldInfo.Module))
+ {
+ return true;
+ }
+
+ return false;
+ }
+
+ private bool IsPublicOnly(bool isPrivate, bool isFamilyAndAssembly, bool isAssembly, Module module)
+ {
+ if (!_publicOnlyModules.TryGetValue(module, out NotAnnotatedStatus value))
+ {
+ value = PopulateAnnotationInfo(module.GetCustomAttributesData());
+ _publicOnlyModules.Add(module, value);
+ }
+
+ if (value == NotAnnotatedStatus.None)
+ {
+ return false;
+ }
+
+ if (((isPrivate || isFamilyAndAssembly) && value.HasFlag(NotAnnotatedStatus.Private)) ||
+ (isAssembly && value.HasFlag(NotAnnotatedStatus.Internal)))
+ {
+ return true;
+ }
+
+ return false;
+ }
+
+ private static NotAnnotatedStatus PopulateAnnotationInfo(IList customAttributes)
+ {
+ foreach (CustomAttributeData attribute in customAttributes)
+ {
+ if (attribute.AttributeType.Name == "NullablePublicOnlyAttribute" &&
+ attribute.AttributeType.Namespace == CompilerServicesNameSpace &&
+ attribute.ConstructorArguments.Count == 1)
+ {
+ if (attribute.ConstructorArguments[0].Value is bool boolValue && boolValue)
+ {
+ return NotAnnotatedStatus.Internal | NotAnnotatedStatus.Private;
+ }
+ else
+ {
+ return NotAnnotatedStatus.Private;
+ }
+ }
+ }
+
+ return NotAnnotatedStatus.None;
+ }
+
+ private NullabilityInfo GetNullabilityInfo(MemberInfo memberInfo, Type type, NullableAttributeStateParser parser)
+ {
+ int index = 0;
+ NullabilityInfo nullability = GetNullabilityInfo(memberInfo, type, parser, ref index);
+
+ if (nullability.ReadState != NullabilityState.Unknown)
+ {
+ TryLoadGenericMetaTypeNullability(memberInfo, nullability);
+ }
+
+ return nullability;
+ }
+
+ private NullabilityInfo GetNullabilityInfo(MemberInfo memberInfo, Type type, NullableAttributeStateParser parser, ref int index)
+ {
+ NullabilityState state = NullabilityState.Unknown;
+ NullabilityInfo? elementState = null;
+ NullabilityInfo[] genericArgumentsState = Array.Empty();
+ Type underlyingType = type;
+
+ if (underlyingType.IsByRef || underlyingType.IsPointer)
+ {
+ underlyingType = underlyingType.GetElementType()!;
+ }
+
+ if (underlyingType.IsValueType)
+ {
+ if (Nullable.GetUnderlyingType(underlyingType) is { } nullableUnderlyingType)
+ {
+ underlyingType = nullableUnderlyingType;
+ state = NullabilityState.Nullable;
+ }
+ else
+ {
+ state = NullabilityState.NotNull;
+ }
+
+ if (underlyingType.IsGenericType)
+ {
+ ++index;
+ }
+ }
+ else
+ {
+ if (!parser.ParseNullableState(index++, ref state)
+ && GetNullableContext(memberInfo) is { } contextState)
+ {
+ state = contextState;
+ }
+
+ if (underlyingType.IsArray)
+ {
+ elementState = GetNullabilityInfo(memberInfo, underlyingType.GetElementType()!, parser, ref index);
+ }
+ }
+
+ if (underlyingType.IsGenericType)
+ {
+ Type[] genericArguments = underlyingType.GetGenericArguments();
+ genericArgumentsState = new NullabilityInfo[genericArguments.Length];
+
+ for (int i = 0; i < genericArguments.Length; i++)
+ {
+ genericArgumentsState[i] = GetNullabilityInfo(memberInfo, genericArguments[i], parser, ref index);
+ }
+ }
+
+ return new NullabilityInfo(type, state, state, elementState, genericArgumentsState);
+ }
+
+ private static NullableAttributeStateParser CreateParser(IList customAttributes)
+ {
+ foreach (CustomAttributeData attribute in customAttributes)
+ {
+ if (attribute.AttributeType.Name == "NullableAttribute" &&
+ attribute.AttributeType.Namespace == CompilerServicesNameSpace &&
+ attribute.ConstructorArguments.Count == 1)
+ {
+ return new NullableAttributeStateParser(attribute.ConstructorArguments[0].Value);
+ }
+ }
+
+ return new NullableAttributeStateParser(null);
+ }
+
+ private void TryLoadGenericMetaTypeNullability(MemberInfo memberInfo, NullabilityInfo nullability)
+ {
+ MemberInfo? metaMember = GetMemberMetadataDefinition(memberInfo);
+ Type? metaType = null;
+ if (metaMember is FieldInfo field)
+ {
+ metaType = field.FieldType;
+ }
+ else if (metaMember is PropertyInfo property)
+ {
+ metaType = GetPropertyMetaType(property);
+ }
+
+ if (metaType != null)
+ {
+ CheckGenericParameters(nullability, metaMember!, metaType, memberInfo.ReflectedType);
+ }
+ }
+
+ private static MemberInfo GetMemberMetadataDefinition(MemberInfo member)
+ {
+ Type? type = member.DeclaringType;
+ if ((type != null) && type.IsGenericType && !type.IsGenericTypeDefinition)
+ {
+ return NullabilityInfoHelpers.GetMemberWithSameMetadataDefinitionAs(type.GetGenericTypeDefinition(), member);
+ }
+
+ return member;
+ }
+
+ private static Type GetPropertyMetaType(PropertyInfo property)
+ {
+ if (property.GetGetMethod(true) is MethodInfo method)
+ {
+ return method.ReturnType;
+ }
+
+ return property.GetSetMethod(true)!.GetParameters()[0].ParameterType;
+ }
+
+ private void CheckGenericParameters(NullabilityInfo nullability, MemberInfo metaMember, Type metaType, Type? reflectedType)
+ {
+ if (metaType.IsGenericParameter)
+ {
+ if (nullability.ReadState == NullabilityState.NotNull)
+ {
+ _ = TryUpdateGenericParameterNullability(nullability, metaType, reflectedType);
+ }
+ }
+ else if (metaType.ContainsGenericParameters)
+ {
+ if (nullability.GenericTypeArguments.Length > 0)
+ {
+ Type[] genericArguments = metaType.GetGenericArguments();
+
+ for (int i = 0; i < genericArguments.Length; i++)
+ {
+ CheckGenericParameters(nullability.GenericTypeArguments[i], metaMember, genericArguments[i], reflectedType);
+ }
+ }
+ else if (nullability.ElementType is { } elementNullability && metaType.IsArray)
+ {
+ CheckGenericParameters(elementNullability, metaMember, metaType.GetElementType()!, reflectedType);
+ }
+
+ // We could also follow this branch for metaType.IsPointer, but since pointers must be unmanaged this
+ // will be a no-op regardless
+ else if (metaType.IsByRef)
+ {
+ CheckGenericParameters(nullability, metaMember, metaType.GetElementType()!, reflectedType);
+ }
+ }
+ }
+
+ private bool TryUpdateGenericParameterNullability(NullabilityInfo nullability, Type genericParameter, Type? reflectedType)
+ {
+ Debug.Assert(genericParameter.IsGenericParameter, "must be generic parameter");
+
+ if (reflectedType is not null
+ && !genericParameter.IsGenericMethodParameter()
+ && TryUpdateGenericTypeParameterNullabilityFromReflectedType(nullability, genericParameter, reflectedType, reflectedType))
+ {
+ return true;
+ }
+
+ if (IsValueTypeOrValueTypeByRef(nullability.Type))
+ {
+ return true;
+ }
+
+ var state = NullabilityState.Unknown;
+ if (CreateParser(genericParameter.GetCustomAttributesData()).ParseNullableState(0, ref state))
+ {
+ nullability.ReadState = state;
+ nullability.WriteState = state;
+ return true;
+ }
+
+ if (GetNullableContext(genericParameter) is { } contextState)
+ {
+ nullability.ReadState = contextState;
+ nullability.WriteState = contextState;
+ return true;
+ }
+
+ return false;
+ }
+
+ private bool TryUpdateGenericTypeParameterNullabilityFromReflectedType(NullabilityInfo nullability, Type genericParameter, Type context, Type reflectedType)
+ {
+ Debug.Assert(genericParameter.IsGenericParameter && !genericParameter.IsGenericMethodParameter(), "must be generic parameter");
+
+ Type contextTypeDefinition = context.IsGenericType && !context.IsGenericTypeDefinition ? context.GetGenericTypeDefinition() : context;
+ if (genericParameter.DeclaringType == contextTypeDefinition)
+ {
+ return false;
+ }
+
+ Type? baseType = contextTypeDefinition.BaseType;
+ if (baseType is null)
+ {
+ return false;
+ }
+
+ if (!baseType.IsGenericType
+ || (baseType.IsGenericTypeDefinition ? baseType : baseType.GetGenericTypeDefinition()) != genericParameter.DeclaringType)
+ {
+ return TryUpdateGenericTypeParameterNullabilityFromReflectedType(nullability, genericParameter, baseType, reflectedType);
+ }
+
+ Type[] genericArguments = baseType.GetGenericArguments();
+ Type genericArgument = genericArguments[genericParameter.GenericParameterPosition];
+ if (genericArgument.IsGenericParameter)
+ {
+ return TryUpdateGenericParameterNullability(nullability, genericArgument, reflectedType);
+ }
+
+ NullableAttributeStateParser parser = CreateParser(contextTypeDefinition.GetCustomAttributesData());
+ int nullabilityStateIndex = 1; // start at 1 since index 0 is the type itself
+ for (int i = 0; i < genericParameter.GenericParameterPosition; i++)
+ {
+ nullabilityStateIndex += CountNullabilityStates(genericArguments[i]);
+ }
+
+ return TryPopulateNullabilityInfo(nullability, parser, ref nullabilityStateIndex);
+
+ static int CountNullabilityStates(Type type)
+ {
+ Type underlyingType = Nullable.GetUnderlyingType(type) ?? type;
+ if (underlyingType.IsGenericType)
+ {
+ int count = 1;
+ foreach (Type genericArgument in underlyingType.GetGenericArguments())
+ {
+ count += CountNullabilityStates(genericArgument);
+ }
+
+ return count;
+ }
+
+ if (underlyingType.HasElementType)
+ {
+ return (underlyingType.IsArray ? 1 : 0) + CountNullabilityStates(underlyingType.GetElementType()!);
+ }
+
+ return type.IsValueType ? 0 : 1;
+ }
+ }
+
+#pragma warning disable SA1204 // Static elements should appear before instance elements
+ private static bool TryPopulateNullabilityInfo(NullabilityInfo nullability, NullableAttributeStateParser parser, ref int index)
+#pragma warning restore SA1204 // Static elements should appear before instance elements
+ {
+ bool isValueType = IsValueTypeOrValueTypeByRef(nullability.Type);
+ if (!isValueType)
+ {
+ var state = NullabilityState.Unknown;
+ if (!parser.ParseNullableState(index, ref state))
+ {
+ return false;
+ }
+
+ nullability.ReadState = state;
+ nullability.WriteState = state;
+ }
+
+ if (!isValueType || (Nullable.GetUnderlyingType(nullability.Type) ?? nullability.Type).IsGenericType)
+ {
+ index++;
+ }
+
+ if (nullability.GenericTypeArguments.Length > 0)
+ {
+ foreach (NullabilityInfo genericTypeArgumentNullability in nullability.GenericTypeArguments)
+ {
+ _ = TryPopulateNullabilityInfo(genericTypeArgumentNullability, parser, ref index);
+ }
+ }
+ else if (nullability.ElementType is { } elementTypeNullability)
+ {
+ _ = TryPopulateNullabilityInfo(elementTypeNullability, parser, ref index);
+ }
+
+ return true;
+ }
+
+ private static NullabilityState TranslateByte(object? value)
+ {
+ return value is byte b ? TranslateByte(b) : NullabilityState.Unknown;
+ }
+
+ private static NullabilityState TranslateByte(byte b) =>
+ b switch
+ {
+ 1 => NullabilityState.NotNull,
+ 2 => NullabilityState.Nullable,
+ _ => NullabilityState.Unknown
+ };
+
+ private static bool IsValueTypeOrValueTypeByRef(Type type) =>
+ type.IsValueType || ((type.IsByRef || type.IsPointer) && type.GetElementType()!.IsValueType);
+
+ private readonly struct NullableAttributeStateParser
+ {
+ private static readonly object UnknownByte = (byte)0;
+
+ private readonly object? _nullableAttributeArgument;
+
+ public NullableAttributeStateParser(object? nullableAttributeArgument)
+ {
+ _nullableAttributeArgument = nullableAttributeArgument;
+ }
+
+ public static NullableAttributeStateParser Unknown => new(UnknownByte);
+
+ public bool ParseNullableState(int index, ref NullabilityState state)
+ {
+ switch (_nullableAttributeArgument)
+ {
+ case byte b:
+ state = TranslateByte(b);
+ return true;
+ case ReadOnlyCollection args
+ when index < args.Count && args[index].Value is byte elementB:
+ state = TranslateByte(elementB);
+ return true;
+ default:
+ return false;
+ }
+ }
+ }
+ }
+}
+#endif
diff --git a/src/LegacySupport/NullabilityInfoContext/NullabilityInfoHelpers.cs b/src/LegacySupport/NullabilityInfoContext/NullabilityInfoHelpers.cs
new file mode 100644
index 00000000000..1ee573a0020
--- /dev/null
+++ b/src/LegacySupport/NullabilityInfoContext/NullabilityInfoHelpers.cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#if !NET6_0_OR_GREATER
+using System.Diagnostics.CodeAnalysis;
+
+#pragma warning disable IDE1006 // Naming Styles
+#pragma warning disable S3011 // Reflection should not be used to increase accessibility of classes, methods, or fields
+
+namespace System.Reflection
+{
+ ///
+ /// Polyfills for System.Private.CoreLib internals.
+ ///
+ [ExcludeFromCodeCoverage]
+ internal static class NullabilityInfoHelpers
+ {
+ public static MemberInfo GetMemberWithSameMetadataDefinitionAs(Type type, MemberInfo member)
+ {
+ const BindingFlags all = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance;
+ foreach (var info in type.GetMembers(all))
+ {
+ if (info.HasSameMetadataDefinitionAs(member))
+ {
+ return info;
+ }
+ }
+
+ throw new MissingMemberException(type.FullName, member.Name);
+ }
+
+ // https://github.com/dotnet/runtime/blob/main/src/coreclr/System.Private.CoreLib/src/System/Reflection/MemberInfo.Internal.cs
+ public static bool HasSameMetadataDefinitionAs(this MemberInfo target, MemberInfo other)
+ {
+ return target.MetadataToken == other.MetadataToken &&
+ target.Module.Equals(other.Module);
+ }
+
+ // https://github.com/dotnet/runtime/issues/23493
+ public static bool IsGenericMethodParameter(this Type target)
+ {
+ return target.IsGenericParameter &&
+ target.DeclaringMethod != null;
+ }
+ }
+}
+#endif
diff --git a/src/Libraries/Microsoft.Extensions.AI.Abstractions/Microsoft.Extensions.AI.Abstractions.csproj b/src/Libraries/Microsoft.Extensions.AI.Abstractions/Microsoft.Extensions.AI.Abstractions.csproj
index 72c354ccb97..15cf9aeecc4 100644
--- a/src/Libraries/Microsoft.Extensions.AI.Abstractions/Microsoft.Extensions.AI.Abstractions.csproj
+++ b/src/Libraries/Microsoft.Extensions.AI.Abstractions/Microsoft.Extensions.AI.Abstractions.csproj
@@ -22,6 +22,7 @@
true
+ true
true
true
true
diff --git a/src/Libraries/Microsoft.Extensions.AI.Abstractions/Utilities/AIJsonUtilities.Schema.Create.cs b/src/Libraries/Microsoft.Extensions.AI.Abstractions/Utilities/AIJsonUtilities.Schema.Create.cs
index 200b470d4d8..c2b81817d79 100644
--- a/src/Libraries/Microsoft.Extensions.AI.Abstractions/Utilities/AIJsonUtilities.Schema.Create.cs
+++ b/src/Libraries/Microsoft.Extensions.AI.Abstractions/Utilities/AIJsonUtilities.Schema.Create.cs
@@ -83,6 +83,7 @@ public static JsonElement CreateFunctionJsonSchema(
title ??= method.GetCustomAttribute()?.DisplayName ?? method.Name;
description ??= method.GetCustomAttribute()?.Description;
+ NullabilityInfoContext nullabilityContext = new();
JsonObject parameterSchemas = new();
JsonArray? requiredProperties = null;
foreach (ParameterInfo parameter in method.GetParameters())
@@ -118,6 +119,7 @@ public static JsonElement CreateFunctionJsonSchema(
JsonNode parameterSchema = CreateJsonSchemaCore(
type: parameter.ParameterType,
parameter: parameter,
+ nullabilityContext: nullabilityContext,
description: parameterDescription,
hasDefaultValue: hasDefaultValue,
defaultValue: defaultValue,
@@ -182,7 +184,7 @@ public static JsonElement CreateJsonSchema(
{
serializerOptions ??= DefaultOptions;
inferenceOptions ??= AIJsonSchemaCreateOptions.Default;
- JsonNode schema = CreateJsonSchemaCore(type, parameter: null, description, hasDefaultValue, defaultValue, serializerOptions, inferenceOptions);
+ JsonNode schema = CreateJsonSchemaCore(type, parameter: null, nullabilityContext: null, description, hasDefaultValue, defaultValue, serializerOptions, inferenceOptions);
// Finally, apply any schema transformations if specified.
if (inferenceOptions.TransformOptions is { } options)
@@ -208,6 +210,7 @@ internal static void ValidateSchemaDocument(JsonElement document, [CallerArgumen
private static JsonNode CreateJsonSchemaCore(
Type? type,
ParameterInfo? parameter,
+ NullabilityInfoContext? nullabilityContext,
string? description,
bool hasDefaultValue,
object? defaultValue,
@@ -338,6 +341,21 @@ JsonNode TransformSchemaNode(JsonSchemaExporterContext schemaExporterContext, Js
objSchema.InsertAtStart(TypePropertyName, new JsonArray { (JsonNode)"string", (JsonNode)"null" });
}
}
+ else if (parameter is not null &&
+ !ctx.TypeInfo.Type.IsValueType &&
+ nullabilityContext?.Create(parameter).WriteState is NullabilityState.Nullable)
+ {
+ // Handle nullable reference type parameters (e.g., object?).
+ if (objSchema.TryGetPropertyValue(TypePropertyName, out JsonNode? typeKeyWord) &&
+ typeKeyWord?.GetValueKind() is JsonValueKind.String)
+ {
+ string typeValue = typeKeyWord.GetValue()!;
+ if (typeValue is not "null")
+ {
+ objSchema[TypePropertyName] = new JsonArray { (JsonNode)typeValue, (JsonNode)"null" };
+ }
+ }
+ }
}
if (ctx.Path.IsEmpty && hasDefaultValue)
diff --git a/test/Libraries/Microsoft.Extensions.AI.Tests/Functions/AIFunctionFactoryTest.cs b/test/Libraries/Microsoft.Extensions.AI.Tests/Functions/AIFunctionFactoryTest.cs
index deea4cbcf13..0b40c67d5d9 100644
--- a/test/Libraries/Microsoft.Extensions.AI.Tests/Functions/AIFunctionFactoryTest.cs
+++ b/test/Libraries/Microsoft.Extensions.AI.Tests/Functions/AIFunctionFactoryTest.cs
@@ -1314,6 +1314,110 @@ public void RegularStaticMethod_NameUnchanged()
Assert.Equal("TestStaticMethod", tool.Name);
}
+ [Fact]
+ public void JsonSchema_NullableValueTypeParameters_AllowNull()
+ {
+ // Test that nullable value type parameters (e.g., int?) generate JSON schemas that allow null values.
+ // This should work on all target frameworks.
+ AIFunction func = AIFunctionFactory.Create(
+ (int? nullableInt, int? nullableIntWithDefault = null) => { });
+
+ JsonElement schema = func.JsonSchema;
+ JsonElement properties = schema.GetProperty("properties");
+
+ // nullableInt should have type ["integer", "null"]
+ JsonElement nullableIntSchema = properties.GetProperty("nullableInt");
+ Assert.True(
+ nullableIntSchema.TryGetProperty("type", out JsonElement nullableIntType),
+ "nullableInt schema should have a 'type' property");
+ Assert.Equal(JsonValueKind.Array, nullableIntType.ValueKind);
+ Assert.Contains("integer", nullableIntType.EnumerateArray().Select(e => e.GetString()));
+ Assert.Contains("null", nullableIntType.EnumerateArray().Select(e => e.GetString()));
+
+ // nullableIntWithDefault should have type ["integer", "null"] and default: null
+ JsonElement nullableIntWithDefaultSchema = properties.GetProperty("nullableIntWithDefault");
+ Assert.True(
+ nullableIntWithDefaultSchema.TryGetProperty("type", out JsonElement nullableIntWithDefaultType),
+ "nullableIntWithDefault schema should have a 'type' property");
+ Assert.Equal(JsonValueKind.Array, nullableIntWithDefaultType.ValueKind);
+ Assert.Contains("integer", nullableIntWithDefaultType.EnumerateArray().Select(e => e.GetString()));
+ Assert.Contains("null", nullableIntWithDefaultType.EnumerateArray().Select(e => e.GetString()));
+ Assert.True(
+ nullableIntWithDefaultSchema.TryGetProperty("default", out JsonElement nullableIntWithDefaultDefault),
+ "nullableIntWithDefault schema should have a 'default' property");
+ Assert.Equal(JsonValueKind.Null, nullableIntWithDefaultDefault.ValueKind);
+
+ // Required array should contain only parameters without default values
+ JsonElement required = schema.GetProperty("required");
+ List requiredParams = required.EnumerateArray().Select(e => e.GetString()!).ToList();
+ Assert.Contains("nullableInt", requiredParams);
+ Assert.DoesNotContain("nullableIntWithDefault", requiredParams);
+ }
+
+ [Fact]
+ public void JsonSchema_NullableReferenceTypeParameters_AllowNull()
+ {
+ // Regression test for https://github.com/dotnet/extensions/issues/7182
+ // Nullable reference type parameters (e.g., string?) should generate JSON schemas that allow null values.
+ AIFunction func = AIFunctionFactory.Create(
+ (string? nullableString, int? nullableInt, string? nullableStringWithDefault = null, int? nullableIntWithDefault = null) => { });
+
+ JsonElement schema = func.JsonSchema;
+ JsonElement properties = schema.GetProperty("properties");
+
+ // nullableString should have type ["string", "null"]
+ JsonElement nullableStringSchema = properties.GetProperty("nullableString");
+ Assert.True(
+ nullableStringSchema.TryGetProperty("type", out JsonElement nullableStringType),
+ "nullableString schema should have a 'type' property");
+ Assert.Equal(JsonValueKind.Array, nullableStringType.ValueKind);
+ Assert.Contains("string", nullableStringType.EnumerateArray().Select(e => e.GetString()));
+ Assert.Contains("null", nullableStringType.EnumerateArray().Select(e => e.GetString()));
+
+ // nullableInt should have type ["integer", "null"]
+ JsonElement nullableIntSchema = properties.GetProperty("nullableInt");
+ Assert.True(
+ nullableIntSchema.TryGetProperty("type", out JsonElement nullableIntType),
+ "nullableInt schema should have a 'type' property");
+ Assert.Equal(JsonValueKind.Array, nullableIntType.ValueKind);
+ Assert.Contains("integer", nullableIntType.EnumerateArray().Select(e => e.GetString()));
+ Assert.Contains("null", nullableIntType.EnumerateArray().Select(e => e.GetString()));
+
+ // nullableStringWithDefault should have type ["string", "null"] and default: null
+ JsonElement nullableStringWithDefaultSchema = properties.GetProperty("nullableStringWithDefault");
+ Assert.True(
+ nullableStringWithDefaultSchema.TryGetProperty("type", out JsonElement nullableStringWithDefaultType),
+ "nullableStringWithDefault schema should have a 'type' property");
+ Assert.Equal(JsonValueKind.Array, nullableStringWithDefaultType.ValueKind);
+ Assert.Contains("string", nullableStringWithDefaultType.EnumerateArray().Select(e => e.GetString()));
+ Assert.Contains("null", nullableStringWithDefaultType.EnumerateArray().Select(e => e.GetString()));
+ Assert.True(
+ nullableStringWithDefaultSchema.TryGetProperty("default", out JsonElement nullableStringWithDefaultDefault),
+ "nullableStringWithDefault schema should have a 'default' property");
+ Assert.Equal(JsonValueKind.Null, nullableStringWithDefaultDefault.ValueKind);
+
+ // nullableIntWithDefault should have type ["integer", "null"] and default: null
+ JsonElement nullableIntWithDefaultSchema = properties.GetProperty("nullableIntWithDefault");
+ Assert.True(
+ nullableIntWithDefaultSchema.TryGetProperty("type", out JsonElement nullableIntWithDefaultType),
+ "nullableIntWithDefault schema should have a 'type' property");
+ Assert.Equal(JsonValueKind.Array, nullableIntWithDefaultType.ValueKind);
+ Assert.Contains("integer", nullableIntWithDefaultType.EnumerateArray().Select(e => e.GetString()));
+ Assert.Contains("null", nullableIntWithDefaultType.EnumerateArray().Select(e => e.GetString()));
+ Assert.True(
+ nullableIntWithDefaultSchema.TryGetProperty("default", out JsonElement nullableIntWithDefaultDefault),
+ "nullableIntWithDefault schema should have a 'default' property");
+ Assert.Equal(JsonValueKind.Null, nullableIntWithDefaultDefault.ValueKind);
+
+ // Required array should contain only parameters without default values
+ JsonElement required = schema.GetProperty("required");
+ List requiredParams = required.EnumerateArray().Select(e => e.GetString()!).ToList();
+ Assert.Contains("nullableString", requiredParams);
+ Assert.Contains("nullableInt", requiredParams);
+ Assert.DoesNotContain("nullableStringWithDefault", requiredParams);
+ Assert.DoesNotContain("nullableIntWithDefault", requiredParams);
+ }
+
[JsonSerializable(typeof(IAsyncEnumerable))]
[JsonSerializable(typeof(int[]))]
[JsonSerializable(typeof(string))]