Support NRT and MSV in required and nullable

.editorconfig

@@ -12,6 +12,10 @@ insert_final_newline = true
 [*.{csproj,json}]
 indent_size = 2
 
+[test/OpenApiClientTests/obj/*.{cs}]
+# Ignore compiler warnings triggered by code auto-generated by NSWag
+dotnet_diagnostic.CS8625.severity = suggestion
+
 [*.{cs}]
 #### .NET Coding Conventions ####
 

src/JsonApiDotNetCore.OpenApi/ResourceFieldAttributeExtensions.cs

@@ -1,21 +1,40 @@
 using System.ComponentModel.DataAnnotations;
+using System.Reflection;
 using JsonApiDotNetCore.Resources.Annotations;
 using Swashbuckle.AspNetCore.SwaggerGen;
 
 namespace JsonApiDotNetCore.OpenApi;
 
 internal static class ResourceFieldAttributeExtensions
 {
+    private static readonly NullabilityInfoContext NullabilityInfoContext = new();
+
     public static bool IsNullable(this ResourceFieldAttribute source)
     {
-        TypeCategory fieldTypeCategory = source.Property.GetTypeCategory();
         bool hasRequiredAttribute = source.Property.HasAttribute<RequiredAttribute>();
 
-        return fieldTypeCategory switch
+        if (hasRequiredAttribute)
         {
-            TypeCategory.NonNullableReferenceType or TypeCategory.ValueType => false,
-            TypeCategory.NullableReferenceType or TypeCategory.NullableValueType => !hasRequiredAttribute,
-            _ => throw new UnreachableCodeException()
-        };
+            // Reflects the following cases, independent of NRT setting
+            //      `[Required] int? Number` => not nullable
+            //      `[Required] int Number` => not nullable
+            //      `[Required] string Text` => not nullable
+            //      `[Required] string? Text` => not nullable
+            //      `[Required] string Text` => not nullable
+            return false;
+        }
+
+        NullabilityInfo nullabilityInfo = NullabilityInfoContext.Create(source.Property);
+
+        //  Reflects the following cases:
+        //    Independent of NRT:
+        //      `int? Number` => nullable
+        //      `int Number` => not nullable
+        //    If NRT is enabled:
+        //      `string? Text` => nullable
+        //      `string Text` => not nullable
+        //    If NRT is disabled:
+        //      `string Text` => nullable
+        return nullabilityInfo.ReadState is not NullabilityState.NotNull;
     }
 }

src/JsonApiDotNetCore.OpenApi/SwaggerComponents/JsonApiSchemaGenerator.cs

@@ -26,6 +26,13 @@ internal sealed class JsonApiSchemaGenerator : ISchemaGenerator
         typeof(NullableToOneRelationshipInRequest<>)
     };
 
+    private static readonly Type[] JsonApiDocumentWithNullableDataOpenTypes =
+    {
+        typeof(NullableSecondaryResourceResponseDocument<>),
+        typeof(NullableResourceIdentifierResponseDocument<>),
+        typeof(NullableToOneRelationshipInRequest<>)
+    };
+
     private readonly ISchemaGenerator _defaultSchemaGenerator;
     private readonly ResourceObjectSchemaGenerator _resourceObjectSchemaGenerator;
     private readonly NullableReferenceSchemaGenerator _nullableReferenceSchemaGenerator;
@@ -58,7 +65,7 @@ public OpenApiSchema GenerateSchema(Type type, SchemaRepository schemaRepository
         {
             OpenApiSchema schema = GenerateJsonApiDocumentSchema(type);
 
-            if (IsDataPropertyNullable(type))
+            if (IsDataPropertyNullableInDocument(type))
             {
                 SetDataObjectSchemaToNullable(schema);
             }
@@ -98,18 +105,11 @@ private static bool IsManyDataDocument(Type documentType)
         return documentType.BaseType!.GetGenericTypeDefinition() == typeof(ManyData<>);
     }
 
-    private static bool IsDataPropertyNullable(Type type)
+    private static bool IsDataPropertyNullableInDocument(Type documentType)
     {
-        PropertyInfo? dataProperty = type.GetProperty(nameof(JsonApiObjectPropertyName.Data));
-
-        if (dataProperty == null)
-        {
-            throw new UnreachableCodeException();
-        }
-
-        TypeCategory typeCategory = dataProperty.GetTypeCategory();
+        Type documentOpenType = documentType.GetGenericTypeDefinition();
 
-        return typeCategory == TypeCategory.NullableReferenceType;
+        return JsonApiDocumentWithNullableDataOpenTypes.Contains(documentOpenType);
     }
 
     private void SetDataObjectSchemaToNullable(OpenApiSchema referenceSchemaForDocument)

src/JsonApiDotNetCore.OpenApi/SwaggerComponents/ResourceFieldObjectSchemaBuilder.cs

@@ -1,6 +1,6 @@
 using System.ComponentModel.DataAnnotations;
 using System.Reflection;
-using System.Text.Json;
+using JsonApiDotNetCore.Configuration;
 using JsonApiDotNetCore.OpenApi.JsonApiObjects;
 using JsonApiDotNetCore.OpenApi.JsonApiObjects.Relationships;
 using JsonApiDotNetCore.OpenApi.JsonApiObjects.ResourceObjects;
@@ -12,35 +12,46 @@ namespace JsonApiDotNetCore.OpenApi.SwaggerComponents;
 
 internal sealed class ResourceFieldObjectSchemaBuilder
 {
-    private static readonly Type[] RelationshipInResponseOpenTypes =
+    private static readonly NullabilityInfoContext NullabilityInfoContext = new();
+
+    private static readonly Type[] RelationshipSchemaInResponseOpenTypes =
     {
         typeof(ToOneRelationshipInResponse<>),
         typeof(ToManyRelationshipInResponse<>),
         typeof(NullableToOneRelationshipInResponse<>)
     };
 
+    private static readonly Type[] NullableRelationshipSchemaOpenTypes =
+    {
+        typeof(NullableToOneRelationshipInRequest<>),
+        typeof(NullableToOneRelationshipInResponse<>)
+    };
+
     private readonly ResourceTypeInfo _resourceTypeInfo;
     private readonly ISchemaRepositoryAccessor _schemaRepositoryAccessor;
     private readonly SchemaGenerator _defaultSchemaGenerator;
     private readonly ResourceTypeSchemaGenerator _resourceTypeSchemaGenerator;
+    private readonly IJsonApiOptions _options;
     private readonly SchemaRepository _resourceSchemaRepository = new();
     private readonly NullableReferenceSchemaGenerator _nullableReferenceSchemaGenerator;
     private readonly IDictionary<string, OpenApiSchema> _schemasForResourceFields;
 
     public ResourceFieldObjectSchemaBuilder(ResourceTypeInfo resourceTypeInfo, ISchemaRepositoryAccessor schemaRepositoryAccessor,
-        SchemaGenerator defaultSchemaGenerator, ResourceTypeSchemaGenerator resourceTypeSchemaGenerator, JsonNamingPolicy? namingPolicy)
+        SchemaGenerator defaultSchemaGenerator, ResourceTypeSchemaGenerator resourceTypeSchemaGenerator, IJsonApiOptions options)
     {
         ArgumentGuard.NotNull(resourceTypeInfo, nameof(resourceTypeInfo));
         ArgumentGuard.NotNull(schemaRepositoryAccessor, nameof(schemaRepositoryAccessor));
         ArgumentGuard.NotNull(defaultSchemaGenerator, nameof(defaultSchemaGenerator));
         ArgumentGuard.NotNull(resourceTypeSchemaGenerator, nameof(resourceTypeSchemaGenerator));
+        ArgumentGuard.NotNull(options, nameof(options));
 
         _resourceTypeInfo = resourceTypeInfo;
         _schemaRepositoryAccessor = schemaRepositoryAccessor;
         _defaultSchemaGenerator = defaultSchemaGenerator;
         _resourceTypeSchemaGenerator = resourceTypeSchemaGenerator;
+        _options = options;
 
-        _nullableReferenceSchemaGenerator = new NullableReferenceSchemaGenerator(schemaRepositoryAccessor, namingPolicy);
+        _nullableReferenceSchemaGenerator = new NullableReferenceSchemaGenerator(schemaRepositoryAccessor, options.SerializerOptions.PropertyNamingPolicy);
         _schemasForResourceFields = GetFieldSchemas();
     }
 
@@ -108,15 +119,14 @@ private bool IsFieldRequired(ResourceFieldAttribute field)
             return false;
         }
 
-        TypeCategory fieldTypeCategory = field.Property.GetTypeCategory();
         bool hasRequiredAttribute = field.Property.HasAttribute<RequiredAttribute>();
 
-        return fieldTypeCategory switch
+        NullabilityInfo nullabilityInfo = NullabilityInfoContext.Create(field.Property);
+
+        return field.Property.PropertyType.IsValueType switch
         {
-            TypeCategory.NonNullableReferenceType => true,
-            TypeCategory.ValueType => hasRequiredAttribute,
-            TypeCategory.NullableReferenceType or TypeCategory.NullableValueType => hasRequiredAttribute,
-            _ => throw new UnreachableCodeException()
+            true => hasRequiredAttribute,
+            false => _options.ValidateModelState ? nullabilityInfo.ReadState == NullabilityState.NotNull || hasRequiredAttribute : hasRequiredAttribute
         };
     }
 
@@ -194,7 +204,9 @@ private OpenApiSchema CreateRelationshipSchema(Type relationshipSchemaType)
 
         OpenApiSchema fullSchema = _schemaRepositoryAccessor.Current.Schemas[referenceSchema.Reference.Id];
 
-        if (IsDataPropertyNullable(relationshipSchemaType))
+        Console.WriteLine(relationshipSchemaType.FullName);
+
+        if (IsDataPropertyNullableInRelationshipSchemaType(relationshipSchemaType))
         {
             fullSchema.Properties[JsonApiObjectPropertyName.Data] =
                 _nullableReferenceSchemaGenerator.GenerateSchema(fullSchema.Properties[JsonApiObjectPropertyName.Data]);
@@ -212,18 +224,12 @@ private static bool IsRelationshipInResponseType(Type relationshipSchemaType)
     {
         Type relationshipSchemaOpenType = relationshipSchemaType.GetGenericTypeDefinition();
 
-        return RelationshipInResponseOpenTypes.Contains(relationshipSchemaOpenType);
+        return RelationshipSchemaInResponseOpenTypes.Contains(relationshipSchemaOpenType);
     }
 
-    private static bool IsDataPropertyNullable(Type type)
+    private static bool IsDataPropertyNullableInRelationshipSchemaType(Type relationshipSchemaType)
     {
-        PropertyInfo? dataProperty = type.GetProperty(nameof(JsonApiObjectPropertyName.Data));
-
-        if (dataProperty == null)
-        {
-            throw new UnreachableCodeException();
-        }
-
-        return dataProperty.GetTypeCategory() == TypeCategory.NullableReferenceType;
+        Type relationshipSchemaOpenType = relationshipSchemaType.GetGenericTypeDefinition();
+        return NullableRelationshipSchemaOpenTypes.Contains(relationshipSchemaOpenType);
     }
 }

src/JsonApiDotNetCore.OpenApi/SwaggerComponents/ResourceObjectSchemaGenerator.cs

@@ -31,7 +31,7 @@ public ResourceObjectSchemaGenerator(SchemaGenerator defaultSchemaGenerator, IRe
         _allowClientGeneratedIds = options.AllowClientGeneratedIds;
 
         _resourceFieldObjectSchemaBuilderFactory = resourceTypeInfo => new ResourceFieldObjectSchemaBuilder(resourceTypeInfo, schemaRepositoryAccessor,
-            defaultSchemaGenerator, _resourceTypeSchemaGenerator, options.SerializerOptions.PropertyNamingPolicy);
+            defaultSchemaGenerator, _resourceTypeSchemaGenerator, options);
     }
 
     public OpenApiSchema GenerateSchema(Type resourceObjectType)

test/OpenApiClientTests/LegacyClient/ApiResponse.cs → test/OpenApiClientTests/ApiResponse.cs

@@ -3,7 +3,7 @@
 
 #pragma warning disable AV1008 // Class should not be static
 
-namespace OpenApiClientTests.LegacyClient;
+namespace OpenApiClientTests;
 
 internal static class ApiResponse
 {

test/OpenApiClientTests/LegacyClient/FakeHttpClientWrapper.cs → test/OpenApiClientTests/FakeHttpClientWrapper.cs

@@ -3,7 +3,7 @@
 using System.Text;
 using JsonApiDotNetCore.OpenApi.Client;
 
-namespace OpenApiClientTests.LegacyClient;
+namespace OpenApiClientTests;
 
 /// <summary>
 /// Enables to inject an outgoing response body and inspect the incoming request.

test/OpenApiClientTests/OpenApiClientTests.csproj

@@ -19,10 +19,6 @@
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="$(AspNetVersion)" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="$(TestSdkVersion)" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
-    <PackageReference Include="NSwag.ApiDescription.Client" Version="13.10.9">
-      <PrivateAssets>all</PrivateAssets>
-      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-    </PackageReference>
     <PackageReference Include="Microsoft.Extensions.ApiDescription.Client" Version="5.0.9">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
@@ -62,5 +58,19 @@
       <CodeGenerator>NSwagCSharp</CodeGenerator>
       <Options>/UseBaseUrl:false /ClientClassAccessModifier:internal /GenerateExceptionClasses:false /AdditionalNamespaceUsages:JsonApiDotNetCore.OpenApi.Client.Exceptions</Options>
     </OpenApiReference>
+    <OpenApiReference Include="SchemaProperties\NullableReferenceTypesEnabled\swagger.g.json">
+      <Namespace>OpenApiClientTests.SchemaProperties.NullableReferenceTypesEnabled.GeneratedCode</Namespace>
+      <ClassName>NullableReferenceTypesEnabledClient</ClassName>
+      <OutputPath>NullableReferenceTypesEnabledClient.cs</OutputPath>
+      <CodeGenerator>NSwagCSharp</CodeGenerator>
+      <Options>/UseBaseUrl:false /ClientClassAccessModifier:internal /GenerateExceptionClasses:false /AdditionalNamespaceUsages:JsonApiDotNetCore.OpenApi.Client.Exceptions /GenerateNullableReferenceTypes:true</Options>
+    </OpenApiReference>
+    <OpenApiReference Include="SchemaProperties\NullableReferenceTypesDisabled\swagger.g.json">
+      <Namespace>OpenApiClientTests.SchemaProperties.NullableReferenceTypesDisabled.GeneratedCode</Namespace>
+      <ClassName>NullableReferenceTypesDisabledClient</ClassName>
+      <OutputPath>NullableReferenceTypesDisabledClient.cs</OutputPath>
+      <CodeGenerator>NSwagCSharp</CodeGenerator>
+      <Options>/UseBaseUrl:false /ClientClassAccessModifier:internal /GenerateExceptionClasses:false /AdditionalNamespaceUsages:JsonApiDotNetCore.OpenApi.Client.Exceptions /GenerateNullableReferenceTypes:false</Options>
+    </OpenApiReference>
   </ItemGroup>
 </Project>

test/OpenApiClientTests/PropertyInfoAssertionsExtension.cs

@@ -0,0 +1,30 @@
+using System.Reflection;
+using FluentAssertions;
+using FluentAssertions.Types;
+
+namespace OpenApiClientTests;
+
+internal static class PropertyInfoAssertionsExtensions
+{
+    private static readonly NullabilityInfoContext NullabilityInfoContext = new();
+
+    [CustomAssertion]
+    public static void BeNullable(this PropertyInfoAssertions source, string because = "", params object[] becauseArgs)
+    {
+        PropertyInfo propertyInfo = source.Subject;
+
+        NullabilityInfo nullabilityInfo = NullabilityInfoContext.Create(propertyInfo);
+
+        nullabilityInfo.ReadState.Should().NotBe(NullabilityState.NotNull, because, becauseArgs);
+    }
+
+    [CustomAssertion]
+    public static void BeNonNullable(this PropertyInfoAssertions source, string because = "", params object[] becauseArgs)
+    {
+        PropertyInfo propertyInfo = source.Subject;
+
+        NullabilityInfo nullabilityInfo = NullabilityInfoContext.Create(propertyInfo);
+
+        nullabilityInfo.ReadState.Should().Be(NullabilityState.NotNull, because, becauseArgs);
+    }
+}

test/OpenApiClientTests/SchemaProperties/NullableReferenceTypesDisabled/GeneratedCode/NullableReferenceTypesDisabledClient.cs

@@ -0,0 +1,14 @@
+using JsonApiDotNetCore.OpenApi.Client;
+using Newtonsoft.Json;
+
+namespace OpenApiClientTests.SchemaProperties.NullableReferenceTypesDisabled.GeneratedCode;
+
+internal partial class NullableReferenceTypesDisabledClient : JsonApiClient
+{
+    partial void UpdateJsonSerializerSettings(JsonSerializerSettings settings)
+    {
+        SetSerializerSettingsForJsonApi(settings);
+
+        settings.Formatting = Formatting.Indented;
+    }
+}

test/OpenApiClientTests/SchemaProperties/NullableReferenceTypesDisabled/NullabilityTests.cs

@@ -0,0 +1,27 @@
+using System.Reflection;
+using FluentAssertions;
+using OpenApiClientTests.SchemaProperties.NullableReferenceTypesDisabled.GeneratedCode;
+using Xunit;
+
+namespace OpenApiClientTests.SchemaProperties.NullableReferenceTypesDisabled;
+
+public sealed class NullabilityTests
+{
+    [Fact]
+    public void Nullability_of_generated_types_is_as_expected()
+    {
+        PropertyInfo[] propertyInfos = typeof(ChickenAttributesInResponse).GetProperties();
+
+        PropertyInfo? propertyInfo = propertyInfos.FirstOrDefault(property => property.Name == nameof(ChickenAttributesInResponse.Name));
+        propertyInfo.Should().BeNullable();
+
+        propertyInfo = propertyInfos.FirstOrDefault(property => property.Name == nameof(ChickenAttributesInResponse.NameOfCurrentFarm));
+        propertyInfo.Should().BeNullable();
+
+        propertyInfo = propertyInfos.FirstOrDefault(property => property.Name == nameof(ChickenAttributesInResponse.Age));
+        propertyInfo.Should().BeNonNullable();
+
+        propertyInfo = propertyInfos.FirstOrDefault(property => property.Name == nameof(ChickenAttributesInResponse.TimeAtCurrentFarmInDays));
+        propertyInfo.Should().BeNullable();
+    }
+}