Factory pattern

Moyou.Aspects/Moyou.Aspects.Factory/AspectOrder.cs

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+using Metalama.Framework.Aspects;
+using Moyou.Aspects.Factory;
+
+[assembly: AspectOrder(AspectOrderDirection.CompileTime, typeof(FactoryMemberAspect), typeof(FactoryAttribute))]

Moyou.Aspects/Moyou.Aspects.Factory/FactoryAttribute.cs

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+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using Metalama.Framework.Advising;
+using Metalama.Framework.Aspects;
+using Metalama.Framework.Code;
+using Metalama.Framework.Diagnostics;
+using Moyou.Diagnostics;
+using Moyou.Extensions;
+
+namespace Moyou.Aspects.Factory;
+
+[AttributeUsage(AttributeTargets.Class)]
+public class FactoryAttribute : TypeAspect
+{
+    private static readonly DiagnosticDefinition<INamedType> ErrorNoSuitableConstructor =
+        new(Errors.Factory.NoSuitableConstructorId, Severity.Error,
+            Errors.Factory.NoSuitableConstructorMessageFormat,
+            Errors.Factory.NoSuitableConstructorTitle,
+            Errors.Factory.NoSuitableConstructorCategory);
+
+    private static readonly DiagnosticDefinition<INamedType> ErrorMultipleMarkedConstructors =
+        new(Errors.Factory.MultipleMarkedConstructorsId, Severity.Error,
+            Errors.Factory.MultipleMarkedConstructorsMessageFormat,
+            Errors.Factory.MultipleMarkedConstructorTitle,
+            Errors.Factory.MultipleMarkedConstructorCategory);
+
+    [SuppressMessage("Usage", "CA2208:Instantiate argument exceptions correctly")] //property is argument
+    public override void BuildAspect(IAspectBuilder<INamedType> builder)
+    {
+        base.BuildAspect(builder);
+
+        //read the annotations from FactoryMemberAspect and process all tuples 
+        var annotations = builder.Target.Enhancements().GetAnnotations<FactoryMemberAnnotation>();
+        var tuples = annotations.Select(annotation => annotation.AsTuple()).ToList();
+        foreach (var tuple in tuples)
+        {
+            AddMemberToFactory(builder, tuple);
+        }
+    }
+
+    private void AddMemberToFactory(IAspectBuilder<INamedType> builder, (INamedType, INamedType) tuple)
+    {
+        var memberType = tuple.Item1;
+        var primaryInterface = tuple.Item2;
+        var trimmedInterfaceName = primaryInterface.Name.StartsWith("I")
+            ? primaryInterface.Name[1..]
+            : primaryInterface.Name;
+        if (memberType.HasPublicDefaultConstructor())
+        {
+            builder.IntroduceMethod(nameof(CreateTemplateDefaultConstructor), IntroductionScope.Instance,
+                buildMethod: methodBuilder =>
+                {
+                    //drop the leading 'I' from the interface in the method name
+                    methodBuilder.Name = $"Create{trimmedInterfaceName}";
+                    methodBuilder.Accessibility = Accessibility.Public;
+                }, args: new { TInterface = primaryInterface, memberType });
+        }
+        else
+        {
+            HandleNonDefaultConstructor(builder, memberType, trimmedInterfaceName, primaryInterface);
+        }
+    }
+
+    private static void HandleNonDefaultConstructor(IAspectBuilder<INamedType> builder, INamedType memberType,
+        string trimmedInterfaceName, INamedType primaryInterface)
+    {
+        IConstructor? constructor;
+        if (memberType.Constructors.Count == 1)
+        {
+            constructor = memberType.Constructors.Single();
+        }
+        else
+        {
+            try
+            {
+                constructor =
+                    memberType.Constructors.SingleOrDefault(ctor => ctor.HasAttribute<FactoryConstructorAttribute>());
+            }
+            catch (InvalidOperationException iox)
+            {
+                //only one constructor with attribute allowed
+                foreach (var markedCtor in memberType.Constructors.Where(ctor => ctor.HasAttribute<FactoryConstructorAttribute>()))
+                {
+                    builder.Diagnostics.Report(ErrorMultipleMarkedConstructors.WithArguments(memberType), markedCtor);
+                }
+
+                return;
+            }
+        }
+
+        if (constructor == null)
+        {
+            //no constructor is marked
+            builder.Diagnostics.Report(ErrorNoSuitableConstructor.WithArguments(memberType), memberType);
+            return;
+        }
+
+        builder.IntroduceMethod(nameof(CreateTemplate), IntroductionScope.Instance, buildMethod: builder =>
+        {
+            builder.Name = $"Create{trimmedInterfaceName}";
+            builder.Accessibility = Accessibility.Public;
+            //add all constructor parameters to factory method
+            foreach (var constructorParameter in constructor.Parameters)
+            {
+                builder.AddParameter(constructorParameter.Name, constructorParameter.Type);
+            }
+        }, args: new { TInterface = primaryInterface, constructor });
+    }
+
+    [Template]
+    public static TInterface CreateTemplateDefaultConstructor<[CompileTime] TInterface>(
+        [CompileTime] INamedType memberType)
+    {
+        var constructor = meta.CompileTime(memberType.Constructors.GetPublicDefaultConstructor());
+        return constructor.Invoke()!;
+    }
+
+    [Template]
+    public static TInterface CreateTemplate<[CompileTime] TInterface>([CompileTime] IConstructor constructor)
+    {
+        return constructor.Invoke(constructor.Parameters.Select(param => (IExpression)param.Value!));
+    }
+}

Moyou.Aspects/Moyou.Aspects.Factory/FactoryAttributeOptions.cs

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+namespace Moyou.Aspects.Factory;
+
+// public class FactoryAttributeOptions : IHierarchicalOptions<INamedType>
+// {
+//     public INamedType? AbstractFactoryType { get; set; }
+//     public object ApplyChanges(object changes, in ApplyChangesContext context)
+//     {
+//         var other = (FactoryAttributeOptions)changes;
+//         return new FactoryAttributeOptions
+//         {
+//             AbstractFactoryType = other.AbstractFactoryType ?? AbstractFactoryType
+//         };
+//     }
+// }

Moyou.Aspects/Moyou.Aspects.Factory/FactoryConstructorAttribute.cs

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+using Metalama.Framework.Aspects;
+
+namespace Moyou.Aspects.Factory;
+
+[AttributeUsage(AttributeTargets.Constructor)]
+[RunTimeOrCompileTime]
+public class FactoryConstructorAttribute : Attribute
+{
+
+}

Moyou.Aspects/Moyou.Aspects.Factory/FactoryMemberAnnotation.cs

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+using Metalama.Framework.Aspects;
+using Metalama.Framework.Code;
+
+namespace Moyou.Aspects.Factory;
+
+[CompileTime]
+public record FactoryMemberAnnotation : IAnnotation<INamedType>
+{
+    public IRef<IDeclaration> FactoryMemberType { get; }
+    public IRef<IDeclaration> PrimaryInterface { get; }
+
+    public FactoryMemberAnnotation(IRef<IDeclaration> factoryMemberType, IRef<IDeclaration> primaryInterface)
+    {
+        FactoryMemberType = factoryMemberType;
+        PrimaryInterface = primaryInterface;
+    }
+
+    public (INamedType, INamedType) AsTuple() => (
+        (INamedType)FactoryMemberType.GetTarget(ReferenceResolutionOptions.Default),
+        (INamedType)PrimaryInterface.GetTarget(ReferenceResolutionOptions.Default));
+}

Moyou.Aspects/Moyou.Aspects.Factory/FactoryMemberAspect.cs

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+using System.Diagnostics.CodeAnalysis;
+using Metalama.Framework.Advising;
+using Metalama.Framework.Aspects;
+using Metalama.Framework.Code;
+
+namespace Moyou.Aspects.Factory;
+
+public class FactoryMemberAspect : IAspect<INamedType>
+{
+    public List<(INamedType, INamedType)> TargetTuples { get; }
+
+    public FactoryMemberAspect(List<(INamedType, INamedType)> targetTuples)
+    {
+        TargetTuples = targetTuples;
+    }
+
+
+    [SuppressMessage("Usage", "CA2208:Instantiate argument exceptions correctly")] //property is argument
+    public void BuildAspect(IAspectBuilder<INamedType> builder)
+    {
+        //write an annotation on the target type containing the factory members and primary interface
+        var annotations = TargetTuples
+            .Select(tup => new FactoryMemberAnnotation(tup.Item1.ToRef(), tup.Item2.ToRef()));
+        foreach (var annotation in annotations)
+        {
+            builder.AddAnnotation(annotation, true);
+        }
+    }
+}

Moyou.Aspects/Moyou.Aspects.Factory/FactoryMemberAttribute.cs

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+using Metalama.Framework.Aspects;
+
+namespace Moyou.Aspects.Factory;
+
+[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct, AllowMultiple = true)]
+[RunTimeOrCompileTime]
+public class FactoryMemberAttribute : Attribute
+{
+    public Type TargetType { get; set; }
+    public Type? PrimaryInterface { get; set; }
+}

Moyou.Aspects/Moyou.Aspects.Factory/FactoryMemberFabric.cs

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+using JetBrains.Annotations;
+using Metalama.Framework.Code;
+using Metalama.Framework.Diagnostics;
+using Metalama.Framework.Fabrics;
+using Moyou.Diagnostics;
+using Moyou.Extensions;
+
+namespace Moyou.Aspects.Factory;
+
+[UsedImplicitly]
+public class FactoryMemberFabric : TransitiveProjectFabric
+{
+    //MOYOU2201
+    private static readonly DiagnosticDefinition<INamedType> ErrorNoTargetTypeInMemberAttribute =
+        new(Errors.Factory.NoTargetTypeInMemberAttributeId, Severity.Error,
+            Errors.Factory.NoTargetTypeInMemberAttributeMessageFormat,
+            Errors.Factory.NoTargetTypeInMemberAttributeTitle,
+            Errors.Factory.NoTargetTypeInMemberAttributeCategory);
+
+    //MOYOU2202
+    private static readonly DiagnosticDefinition<INamedType> ErrorTypeDoesntImplementAnyInterfaces =
+        new(Errors.Factory.TypeDoesntImplementAnyInterfacesId, Severity.Error,
+            Errors.Factory.TypeDoesntImplementAnyInterfacesMessageFormat,
+            Errors.Factory.TypeDoesntImplementAnyInterfacesTitle,
+            Errors.Factory.TypeDoesntImplementAnyInterfacesCategory);
+
+    //MOYOU2203
+    private static readonly DiagnosticDefinition<INamedType> ErrorAmbiguousInterfacesOnTargetType =
+        new(Errors.Factory.AmbiguousInterfacesOnTargetTypeId, Severity.Error,
+            Errors.Factory.AmbiguousInterfacesOnTargetTypeMessageFormat,
+            Errors.Factory.AmbiguousInterfacesOnTargetTypeTitle,
+            Errors.Factory.AmbiguousInterfacesOnTargetTypeCategory);
+
+    //MOYOU2204
+    private static readonly DiagnosticDefinition<INamedType>
+        ErrorTargetTypeDoesntImplementPrimaryInterface =
+            new(Errors.Factory.TargetTypeDoesntImplementPrimaryInterfaceId, Severity.Error,
+                Errors.Factory.TargetTypeDoesntImplementPrimaryInterfaceMessageFormat,
+                Errors.Factory.TargetTypeDoesntImplementPrimaryInterfaceTitle,
+                Errors.Factory.TargetTypeDoesntImplementPrimaryInterfaceCategory);
+
+    public override void AmendProject(IProjectAmender amender)
+    {
+        var types = amender
+            .SelectTypes()
+            .Where(type => type.HasAttribute<FactoryMemberAttribute>());
+
+        //MOYOU2201 no target type
+        types
+            .Where(type => type
+                .Attributes
+                .Where(IsFactoryMemberAttribute)
+                .Any(NoTargetTypeInAttribute)
+            )
+            .ReportDiagnostic(type => ErrorNoTargetTypeInMemberAttribute.WithArguments(type));
+
+        //MOYOU2202 no implemented interfaces
+        types
+            .Where(type => type
+                .Attributes
+                .Where(IsFactoryMemberAttribute)
+                .Any(TargetTypeImplementsNoInterfaces)
+            )
+            .ReportDiagnostic(type => ErrorTypeDoesntImplementAnyInterfaces.WithArguments(type));
+
+        //MOYOU2203 ambiguous interfaces
+        types
+            .Where(type => type
+                .Attributes
+                .Where(IsFactoryMemberAttribute)
+                .Where(TargetTypeInAttribute)
+                .Where(TargetTypeImplementsMultipleInterfaces)
+                .Any(NoPrimaryInterfaceInAttribute)
+            )
+            .ReportDiagnostic(type => ErrorAmbiguousInterfacesOnTargetType.WithArguments(type));
+
+        //MOYOU2204 target type doesn't implement primary interface
+        types
+            .Where(type => type
+                .Attributes
+                .Where(IsFactoryMemberAttribute)
+                .Where(TargetTypeInAttribute)
+                .Any(TargetTypeDoesNotImplementPrimaryInterface)
+            )
+            .ReportDiagnostic(type => ErrorTargetTypeDoesntImplementPrimaryInterface.WithArguments(type));
+
+        types.AddAspect(type => BuildAspect(type, amender));
+    }
+
+    private static bool TargetTypeImplementsMultipleInterfaces(IAttribute attribute)
+    {
+        var targetType = (INamedType)attribute.NamedArguments[nameof(FactoryMemberAttribute.TargetType)].Value!;
+        return targetType.ImplementedInterfaces.Count > 1;
+    }
+
+    private static bool IsFactoryMemberAttribute(IAttribute attribute)
+    {
+        return attribute.Type.FullName == typeof(FactoryMemberAttribute).FullName;
+    }
+
+    private static bool NoTargetTypeInAttribute(IAttribute attribute)
+    {
+        return !attribute.TryGetNamedArgument(nameof(FactoryMemberAttribute.TargetType), out _);
+    }
+
+    private static bool NoPrimaryInterfaceInAttribute(IAttribute attribute)
+    {
+        return !attribute.TryGetNamedArgument(nameof(FactoryMemberAttribute.PrimaryInterface), out _);
+    }
+
+    private static bool TargetTypeInAttribute(IAttribute attribute)
+    {
+        return attribute.TryGetNamedArgument(nameof(FactoryMemberAttribute.TargetType), out _);
+    }
+
+    private static bool TargetTypeImplementsNoInterfaces(IAttribute attribute)
+    {
+        return attribute.TryGetNamedArgument(nameof(FactoryMemberAttribute.TargetType), out var targetType) &&
+               ((INamedType)targetType.Value!).ImplementedInterfaces.Count == 0;
+    }
+
+    private static bool TargetTypeDoesNotImplementPrimaryInterface(IAttribute attribute)
+    {
+        var targetType = (INamedType)attribute.NamedArguments[nameof(FactoryMemberAttribute.TargetType)].Value!;
+        return attribute.TryGetNamedArgument(nameof(FactoryMemberAttribute.PrimaryInterface), out var primaryInterface) && !targetType.ImplementedInterfaces.Contains((INamedType)primaryInterface.Value!);
+    }
+
+    private static FactoryMemberAspect BuildAspect(INamedType type, IProjectAmender amender)
+    {
+        var memberAttributes = type
+            .Attributes
+            .Where(attr => attr.Type.FullName == typeof(FactoryMemberAttribute).FullName);
+        var targetTuples = GetTypeTuplesFromAttributes(type, memberAttributes);
+        var aspect = new FactoryMemberAspect(targetTuples);
+        return aspect;
+    }
+
+    private static List<(INamedType, INamedType?)> GetTypeTuplesFromAttributes(INamedType factoryType,
+        IEnumerable<IAttribute> memberAttributes)
+    {
+        return memberAttributes
+            .Select(GetTypeAndInterfaceTuple)
+            .Where(tuple => tuple.HasValue)
+            .Select(tuple => tuple.Value)
+            .ToList();
+
+        (INamedType, INamedType?)? GetTypeAndInterfaceTuple(IAttribute attr)
+        {
+            if (!attr.NamedArguments.TryGetValue(nameof(FactoryMemberAttribute.TargetType), out var targetTypeConstant))
+                return null; //MOYOU2201
+            var targetType = (INamedType)targetTypeConstant.Value!;
+            var implementedInterfaces = targetType.ImplementedInterfaces;
+            if (!attr.NamedArguments.TryGetValue(nameof(FactoryMemberAttribute.PrimaryInterface),
+                    out var primaryInterface))
+                return implementedInterfaces.Count == 1 ? (targetType, implementedInterfaces.First()) : null; //MOYOU2202 //MOYOU2203
+            var primaryInterfaceType = (INamedType)primaryInterface.Value!;
+            if (implementedInterfaces.Contains(primaryInterfaceType))
+                return (targetType, primaryInterface.Value as INamedType);
+            return null; //MOYOU2204
+
+        }
+    }
+}