feat: add UnsafeMemberAccessor for private property and fields

.csharpierrc.yaml

@@ -8,6 +8,7 @@ preprocessorSymbolSets:
   - "SYSTEM_PRIVATE_CORELIB"
   - "NETSTANDARD2_0"
   - "ROSLYN4_4_OR_GREATER"
+  - "ROSLYN4_7_OR_GREATER"
   - "NET6_0_OR_GREATER"
   - "NET7_0_OR_GREATER"
   - "NET8_0_OR_GREATER"

docs/docs/configuration/analyzer-diagnostics.mdx

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 14
+sidebar_position: 15
 description: A list of all analyzer diagnostics used by Mapperly and how to configure them.
 ---
 

docs/docs/configuration/conversions.md

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 13
+sidebar_position: 14
 description: A list of conversions supported by Mapperly
 ---
 

docs/docs/configuration/generated-source.mdx

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 15
+sidebar_position: 16
 description: How to inspect and check in the generated source into a version control system (VCS, GIT, ...)
 ---
 

docs/docs/configuration/private-member-mapping.md

@@ -0,0 +1,62 @@
+---
+sidebar_position: 12
+description: Private member mapping
+---
+
+# Private member mapping
+
+As of .NET 8.0, Mapperly supports mapping members that are normally inaccessible like `private` or `protected` properties. This is made possible by using the [UnsafeAccessorAttribute](https://learn.microsoft.com/en-us/dotnet/api/system.runtime.compilerservices.unsafeaccessorattribute) which lets Mapperly access normally inaccessible members with zero overhead while being completely AOT safe.
+
+By default `IncludedMembers` is set to `MemberVisibility.AllAccessible` which will configure Mapperly to map members of all accessibility levels as long as they are ordinarily accessible. To enable unsafe accessor usage, set `IncludedMembers` to `MemberVisibility.All`. Mapperly will then try to map members of all accessibilities, including ones that are not usually visible to external types.
+
+```csharp
+public class Fruit
+{
+    private bool _isSeeded;
+
+    public string Name { get; set; }
+
+    private int Sweetness { get; set; }
+}
+
+// highlight-start
+[Mapper(IncludedMembers = MemberVisibility.All)]
+// highlight-end
+public partial class FruitMapper
+{
+    public partial FruitDto ToDto(Fruit fruit);
+}
+```
+
+## Generated code
+
+```csharp
+public partial class FruitMapper
+{
+    private partial global::FruitDto ToDto(global::Fruit source)
+    {
+        var target = new global::FruitDto();
+        target.GetIsSeeded1() = source.GetIsSeeded();
+        target.Name = source.Name;
+        target.SetSweetness(source.GetSweetness());
+        return target;
+    }
+}
+
+static file class UnsafeAccessor
+{
+    [global::System.Runtime.CompilerServices.UnsafeAccessor(global::System.Runtime.CompilerServices.UnsafeAccessorKind.Field, Name = "_isSeeded")]
+    public static extern ref bool GetSeeded(this global::Fruit target);
+
+    [global::System.Runtime.CompilerServices.UnsafeAccessor(global::System.Runtime.CompilerServices.UnsafeAccessorKind.Field, Name = "_isSeeded")]
+    public static extern ref bool GetSeeded1(this global::FruitDto target);
+
+    [global::System.Runtime.CompilerServices.UnsafeAccessor(global::System.Runtime.CompilerServices.UnsafeAccessorKind.Method, Name = "get_Sweetness")]
+    public static extern int GetSweetness(this global::Fruit source);
+
+    [global::System.Runtime.CompilerServices.UnsafeAccessor(global::System.Runtime.CompilerServices.UnsafeAccessorKind.Method, Name = "set_Sweetness")]
+    public static extern void SetSweetness(this global::FruitDto target, int value);
+}
+```
+
+Here Mapperly generates a file scoped class containing extension method for each internal member for both the source and target. Mapperly then uses the extension methods to get and set the members. Note that this uses zero reflection and is as performant as using an ordinary property or field.

docs/docs/configuration/queryable-projections.mdx

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 12
+sidebar_position: 13
 description: Use queryable projections to map queryable objects and optimize ORM performance
 ---
 

src/Riok.Mapperly.Abstractions/MapperAttribute.cs

@@ -92,4 +92,9 @@ public class MapperAttribute : Attribute
     /// By default this is <see cref="RequiredMappingStrategy.Both"/>, emitting warnings for unmapped source and target members.
     /// </summary>
     public RequiredMappingStrategy RequiredMappingStrategy { get; set; } = RequiredMappingStrategy.Both;
+
+    /// <summary>
+    /// Determines the access level of members that Mapperly will map.
+    /// </summary>
+    public MemberVisibility IncludedMembers { get; set; } = MemberVisibility.AllAccessible;
 }

src/Riok.Mapperly.Abstractions/MemberVisibility.cs

@@ -0,0 +1,45 @@
+namespace Riok.Mapperly.Abstractions;
+
+/// <summary>
+/// Determines what member accessibility Mapperly will attempt to map.
+/// </summary>
+[Flags]
+public enum MemberVisibility
+{
+    /// <summary>
+    /// Maps all accessible members.
+    /// </summary>
+    AllAccessible = All | Accessible,
+
+    /// <summary>
+    /// Maps all members, even members which are not directly accessible by the mapper are mapped
+    /// by using accessors with the UnsafeAccessorAttribute. This can only be used for .NET 8.0 and later.
+    /// </summary>
+    All = Public | Internal | Protected | Private,
+
+    /// <summary>
+    /// Maps only accessible members.
+    /// If not set, the UnsafeAccessorAttribute is used to generate mappings for inaccessible members.
+    /// </summary>
+    Accessible = 1 << 0,
+
+    /// <summary>
+    /// Maps public members.
+    /// </summary>
+    Public = 1 << 1,
+
+    /// <summary>
+    /// Maps internal members.
+    /// </summary>
+    Internal = 1 << 2,
+
+    /// <summary>
+    /// Maps protected members.
+    /// </summary>
+    Protected = 1 << 3,
+
+    /// <summary>
+    /// Maps private members.
+    /// </summary>
+    Private = 1 << 4,
+}

src/Riok.Mapperly.Abstractions/PublicAPI.Shipped.txt

@@ -119,3 +119,13 @@ Riok.Mapperly.Abstractions.RequiredMappingStrategy.Both = -1 -> Riok.Mapperly.Ab
 Riok.Mapperly.Abstractions.RequiredMappingStrategy.None = 0 -> Riok.Mapperly.Abstractions.RequiredMappingStrategy
 Riok.Mapperly.Abstractions.RequiredMappingStrategy.Source = 1 -> Riok.Mapperly.Abstractions.RequiredMappingStrategy
 Riok.Mapperly.Abstractions.RequiredMappingStrategy.Target = 2 -> Riok.Mapperly.Abstractions.RequiredMappingStrategy
+Riok.Mapperly.Abstractions.MapperAttribute.IncludedMembers.get -> Riok.Mapperly.Abstractions.MemberVisibility
+Riok.Mapperly.Abstractions.MapperAttribute.IncludedMembers.set -> void
+Riok.Mapperly.Abstractions.MemberVisibility
+Riok.Mapperly.Abstractions.MemberVisibility.Accessible = 1 -> Riok.Mapperly.Abstractions.MemberVisibility
+Riok.Mapperly.Abstractions.MemberVisibility.All = Riok.Mapperly.Abstractions.MemberVisibility.Public | Riok.Mapperly.Abstractions.MemberVisibility.Internal | Riok.Mapperly.Abstractions.MemberVisibility.Protected | Riok.Mapperly.Abstractions.MemberVisibility.Private -> Riok.Mapperly.Abstractions.MemberVisibility
+Riok.Mapperly.Abstractions.MemberVisibility.AllAccessible = Riok.Mapperly.Abstractions.MemberVisibility.Accessible | Riok.Mapperly.Abstractions.MemberVisibility.All -> Riok.Mapperly.Abstractions.MemberVisibility
+Riok.Mapperly.Abstractions.MemberVisibility.Internal = 4 -> Riok.Mapperly.Abstractions.MemberVisibility
+Riok.Mapperly.Abstractions.MemberVisibility.Private = 16 -> Riok.Mapperly.Abstractions.MemberVisibility
+Riok.Mapperly.Abstractions.MemberVisibility.Protected = 8 -> Riok.Mapperly.Abstractions.MemberVisibility
+Riok.Mapperly.Abstractions.MemberVisibility.Public = 2 -> Riok.Mapperly.Abstractions.MemberVisibility

src/Riok.Mapperly/AnalyzerReleases.Shipped.md

@@ -125,3 +125,4 @@ Rule ID | Category | Severity | Notes
 --------|----------|----------|-------
 RMG051  | Mapper   | Warning  | Invalid ignore source member found, nested ignores are not supported
 RMG052  | Mapper   | Warning  | Invalid ignore target member found, nested ignores are not supported
+RMG053  | Mapper   | Error    | The flag MemberVisibility.Accessible cannot be disabled, this feature requires .NET 8.0 or greater

src/Riok.Mapperly/Configuration/MapperConfiguration.cs

@@ -98,4 +98,9 @@ public record MapperConfiguration
     /// By default this is <see cref="RequiredMappingStrategy.Both"/>, emitting warnings for unmapped source and target members.
     /// </summary>
     public RequiredMappingStrategy? RequiredMappingStrategy { get; init; }
+
+    /// <summary>
+    /// Determines the access level of members that Mapperly will map.
+    /// </summary>
+    public MemberVisibility? IncludedMembers { get; init; }
 }

src/Riok.Mapperly/Configuration/MapperConfigurationMerger.cs

@@ -51,6 +51,9 @@ public static MapperAttribute Merge(MapperConfiguration mapperConfiguration, Map
             ?? defaultMapperConfiguration.RequiredMappingStrategy
             ?? mapper.RequiredMappingStrategy;
 
+        mapper.IncludedMembers =
+            mapperConfiguration.IncludedMembers ?? defaultMapperConfiguration.IncludedMembers ?? mapper.IncludedMembers;
+
         return mapper;
     }
 }

src/Riok.Mapperly/Descriptors/DescriptorBuilder.cs

@@ -1,4 +1,5 @@
 using Microsoft.CodeAnalysis;
+using Riok.Mapperly.Abstractions;
 using Riok.Mapperly.Abstractions.ReferenceHandling;
 using Riok.Mapperly.Configuration;
 using Riok.Mapperly.Descriptors.ExternalMappings;
@@ -21,6 +22,8 @@ public class DescriptorBuilder
     private readonly MappingBodyBuilder _mappingBodyBuilder;
     private readonly SimpleMappingBuilderContext _builderContext;
     private readonly List<Diagnostic> _diagnostics = new();
+    private readonly UnsafeAccessorContext _unsafeAccessorContext;
+    private readonly MapperConfigurationReader _configurationReader;
 
     private ObjectFactoryCollection _objectFactories = ObjectFactoryCollection.Empty;
 
@@ -34,14 +37,18 @@ MapperConfiguration defaultMapperConfiguration
         _mapperDescriptor = new MapperDescriptor(mapperDeclaration, _methodNameBuilder);
         _symbolAccessor = symbolAccessor;
         _mappingBodyBuilder = new MappingBodyBuilder(_mappings);
+        _unsafeAccessorContext = new UnsafeAccessorContext(_methodNameBuilder, symbolAccessor);
 
         var attributeAccessor = new AttributeDataAccessor(symbolAccessor);
+        _configurationReader = new MapperConfigurationReader(attributeAccessor, mapperDeclaration.Symbol, defaultMapperConfiguration);
+
         _builderContext = new SimpleMappingBuilderContext(
             compilationContext,
-            new MapperConfigurationReader(attributeAccessor, mapperDeclaration.Symbol, defaultMapperConfiguration),
+            _configurationReader,
             _symbolAccessor,
             attributeAccessor,
             _mapperDescriptor,
+            _unsafeAccessorContext,
             _diagnostics,
             new MappingBuilder(_mappings),
             new ExistingTargetMappingBuilder(_mappings)
@@ -50,6 +57,7 @@ MapperConfiguration defaultMapperConfiguration
 
     public (MapperDescriptor descriptor, IReadOnlyCollection<Diagnostic> diagnostics) Build(CancellationToken cancellationToken)
     {
+        ConfigureMemberVisibility();
         ReserveMethodNames();
         ExtractObjectFactories();
         ExtractUserMappings();
@@ -59,9 +67,33 @@ MapperConfiguration defaultMapperConfiguration
         TemplateResolver.AddRequiredTemplates(_builderContext.MapperConfiguration, _mappings, _mapperDescriptor);
         BuildReferenceHandlingParameters();
         AddMappingsToDescriptor();
+        AddAccessorsToDescriptor();
         return (_mapperDescriptor, _diagnostics);
     }
 
+    /// <summary>
+    /// If <see cref="MemberVisibility.Accessible"/> is not set and the roslyn version does not have UnsafeAccessors
+    /// then emit a diagnostic and update the <see cref="MemberVisibility"/> for <see cref="SymbolAccessor"/>.
+    /// </summary>
+    private void ConfigureMemberVisibility()
+    {
+        var includedMembers = _configurationReader.Mapper.IncludedMembers;
+#if ROSLYN4_7_OR_GREATER
+        _symbolAccessor.SetMemberVisibility(includedMembers);
+#else
+        if (includedMembers.HasFlag(MemberVisibility.Accessible))
+            return;
+
+        _diagnostics.Add(
+            Diagnostic.Create(
+                Riok.Mapperly.Diagnostics.DiagnosticDescriptors.UnsafeAccessorNotAvailable,
+                _mapperDescriptor.Syntax.GetLocation()
+            )
+        );
+        _symbolAccessor.SetMemberVisibility(includedMembers | MemberVisibility.Accessible);
+#endif
+    }
+
     private void ReserveMethodNames()
     {
         foreach (var methodSymbol in _symbolAccessor.GetAllMembers(_mapperDescriptor.Symbol))
@@ -127,4 +159,10 @@ private void AddMappingsToDescriptor()
             _mapperDescriptor.AddTypeMapping(mapping);
         }
     }
+
+    private void AddAccessorsToDescriptor()
+    {
+        // add generated accessors to the mapper
+        _mapperDescriptor.AddUnsafeAccessors(_unsafeAccessorContext.UnsafeAccessors);
+    }
 }

src/Riok.Mapperly/Descriptors/MapperDescriptor.cs

@@ -2,6 +2,7 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Riok.Mapperly.Descriptors.Mappings;
+using Riok.Mapperly.Descriptors.Mappings.MemberMappings.UnsafeAccess;
 using Riok.Mapperly.Helpers;
 using Riok.Mapperly.Symbols;
 using Riok.Mapperly.Templates;
@@ -12,6 +13,7 @@ public class MapperDescriptor
 {
     private readonly MapperDeclaration _declaration;
     private readonly List<MethodMapping> _methodMappings = new();
+    private readonly List<IUnsafeAccessor> _unsafeAccessors = new();
     private readonly HashSet<TemplateReference> _requiredTemplates = new();
 
     public MapperDescriptor(MapperDeclaration declaration, UniqueNameBuilder nameBuilder)
@@ -40,10 +42,14 @@ public MapperDescriptor(MapperDeclaration declaration, UniqueNameBuilder nameBui
 
     public IReadOnlyCollection<MethodMapping> MethodTypeMappings => _methodMappings;
 
-    public void AddTypeMapping(MethodMapping mapping) => _methodMappings.Add(mapping);
+    public IReadOnlyCollection<IUnsafeAccessor> UnsafeAccessors => _unsafeAccessors;
 
     public void AddRequiredTemplate(TemplateReference template) => _requiredTemplates.Add(template);
 
+    public void AddTypeMapping(MethodMapping mapping) => _methodMappings.Add(mapping);
+
+    public void AddUnsafeAccessors(IEnumerable<IUnsafeAccessor> accessors) => _unsafeAccessors.AddRange(accessors);
+
     private string BuildName(INamedTypeSymbol symbol)
     {
         if (symbol.ContainingType == null)

src/Riok.Mapperly/Descriptors/MappingBodyBuilders/BuilderContext/MembersContainerBuilderContext.cs

@@ -48,7 +48,18 @@ private void AddNullMemberInitializers(IMemberAssignmentMappingContainer contain
                 continue;
             }
 
-            container.AddMemberMappingContainer(new MemberNullAssignmentInitializerMapping(nullablePath));
+            var setterNullablePath = SetterMemberPath.Build(BuilderContext, nullablePath);
+
+            if (setterNullablePath.IsMethod)
+            {
+                var getterNullablePath = GetterMemberPath.Build(BuilderContext, nullablePath);
+                container.AddMemberMappingContainer(
+                    new MethodMemberNullAssignmentInitializerMapping(setterNullablePath, getterNullablePath)
+                );
+                continue;
+            }
+
+            container.AddMemberMappingContainer(new MemberNullAssignmentInitializerMapping(setterNullablePath));
         }
     }
 
@@ -75,7 +86,7 @@ private MemberNullDelegateAssignmentMapping GetOrCreateNullDelegateMappingForPat
         }
 
         mapping = new MemberNullDelegateAssignmentMapping(
-            nullConditionSourcePath,
+            GetterMemberPath.Build(BuilderContext, nullConditionSourcePath),
             parentMapping,
             BuilderContext.MapperConfiguration.ThrowOnPropertyMappingNullMismatch,
             needsNullSafeAccess

src/Riok.Mapperly/Descriptors/MappingBodyBuilders/NewInstanceObjectMemberMappingBodyBuilder.cs

@@ -179,14 +179,17 @@ MemberPath sourcePath
             nullFallback = ctx.BuilderContext.GetNullFallbackValue(targetMember.Type);
         }
 
+        var getterSourcePath = GetterMemberPath.Build(ctx.BuilderContext, sourcePath);
+        var setterTargetPath = SetterMemberPath.Build(ctx.BuilderContext, targetPath);
+
         var memberMapping = new NullMemberMapping(
             delegateMapping,
-            sourcePath,
+            getterSourcePath,
             targetMember.Type,
             nullFallback,
             !ctx.BuilderContext.IsExpression
         );
-        var memberAssignmentMapping = new MemberAssignmentMapping(targetPath, memberMapping);
+        var memberAssignmentMapping = new MemberAssignmentMapping(setterTargetPath, memberMapping);
         ctx.AddInitMemberMapping(memberAssignmentMapping);
     }
 
@@ -203,7 +206,7 @@ private static void BuildConstructorMapping(INewInstanceBuilderContext<IMapping>
         // then by descending parameter count
         // ctors annotated with [Obsolete] are considered last unless they have a MapperConstructor attribute set
         var ctorCandidates = namedTargetType.InstanceConstructors
-            .Where(ctor => ctx.BuilderContext.SymbolAccessor.IsAccessible(ctor))
+            .Where(ctor => ctx.BuilderContext.SymbolAccessor.IsDirectlyAccessible(ctor))
             .OrderByDescending(x => ctx.BuilderContext.SymbolAccessor.HasAttribute<MapperConstructorAttribute>(x))
             .ThenBy(x => ctx.BuilderContext.SymbolAccessor.HasAttribute<MapperConstructorAttribute>(x))
             .ThenByDescending(x => x.Parameters.Length == 0)
@@ -285,9 +288,11 @@ private static bool TryBuildConstructorMapping(
                 return false;
             }
 
+            var getterSourcePath = GetterMemberPath.Build(ctx.BuilderContext, sourcePath);
+
             var memberMapping = new NullMemberMapping(
                 delegateMapping,
-                sourcePath,
+                getterSourcePath,
                 paramType,
                 ctx.BuilderContext.GetNullFallbackValue(paramType),
                 !ctx.BuilderContext.IsExpression

src/Riok.Mapperly/Descriptors/MappingBodyBuilders/NewValueTupleMappingBodyBuilder.cs

@@ -111,9 +111,11 @@ out HashSet<string> mappedTargetMemberNames
                 return false;
             }
 
+            var getterSourcePath = GetterMemberPath.Build(ctx.BuilderContext, sourcePath);
+
             var memberMapping = new NullMemberMapping(
                 delegateMapping,
-                sourcePath,
+                getterSourcePath,
                 paramType,
                 ctx.BuilderContext.GetNullFallbackValue(paramType),
                 !ctx.BuilderContext.IsExpression