Added dynamic query building for resources with constructor parameters

Author: Bart Koelman

src/Examples/JsonApiDotNetCoreExample/Data/AppDbContext.cs

@@ -71,6 +71,11 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
                 .HasForeignKey<Person>(p => p.PassportId)
                 .OnDelete(DeleteBehavior.SetNull);
 
+            modelBuilder.Entity<Passport>()
+                .HasMany(passport => passport.GrantedVisas)
+                .WithOne()
+                .OnDelete(DeleteBehavior.Cascade);
+
             modelBuilder.Entity<TodoItem>()
                 .HasOne(p => p.OneToOnePerson)
                 .WithOne(p => p.OneToOneTodoItem)

src/JsonApiDotNetCore/Data/DefaultResourceRepository.cs

@@ -4,6 +4,7 @@
 using System.Linq;
 using System.Threading.Tasks;
 using JsonApiDotNetCore.Extensions;
+using JsonApiDotNetCore.Internal;
 using JsonApiDotNetCore.Internal.Contracts;
 using JsonApiDotNetCore.Internal.Generics;
 using JsonApiDotNetCore.Internal.Query;
@@ -27,18 +28,21 @@ public class DefaultResourceRepository<TResource, TId> : IResourceRepository<TRe
         private readonly DbSet<TResource> _dbSet;
         private readonly IResourceGraph _resourceGraph;
         private readonly IGenericServiceFactory _genericServiceFactory;
+        private readonly IResourceFactory _resourceFactory;
         private readonly ILogger<DefaultResourceRepository<TResource, TId>> _logger;
 
         public DefaultResourceRepository(
             ITargetedFields targetedFields,
             IDbContextResolver contextResolver,
             IResourceGraph resourceGraph,
             IGenericServiceFactory genericServiceFactory,
+            IResourceFactory resourceFactory,
             ILoggerFactory loggerFactory)
         {
             _targetedFields = targetedFields;
             _resourceGraph = resourceGraph;
             _genericServiceFactory = genericServiceFactory;
+            _resourceFactory = resourceFactory;
             _context = contextResolver.GetContext();
             _dbSet = _context.Set<TResource>();
             _logger = loggerFactory.CreateLogger<DefaultResourceRepository<TResource, TId>>();
@@ -66,7 +70,7 @@ public virtual IQueryable<TResource> Select(IQueryable<TResource> entities, IEnu
         {
             _logger.LogTrace($"Entering {nameof(Select)}({nameof(entities)}, {nameof(propertyNames)}).");
 
-            return entities.Select(propertyNames);
+            return entities.Select(propertyNames, _resourceFactory);
         }
 
         /// <inheritdoc />
@@ -468,8 +472,9 @@ public DefaultResourceRepository(
             IDbContextResolver contextResolver, 
             IResourceGraph resourceGraph, 
             IGenericServiceFactory genericServiceFactory,
+            IResourceFactory resourceFactory,
             ILoggerFactory loggerFactory)
-            : base(targetedFields, contextResolver, resourceGraph, genericServiceFactory, loggerFactory) 
+            : base(targetedFields, contextResolver, resourceGraph, genericServiceFactory, resourceFactory, loggerFactory) 
         { }
     }
 }

src/JsonApiDotNetCore/Extensions/QueryableExtensions.cs

@@ -63,9 +63,9 @@ public static IQueryable<TSource> Filter<TSource>(this IQueryable<TSource> sourc
             return CallGenericWhereMethod(source, filterQuery);
         }
 
-        public static IQueryable<TSource> Select<TSource>(this IQueryable<TSource> source, IEnumerable<string> columns)
+        public static IQueryable<TSource> Select<TSource>(this IQueryable<TSource> source, IEnumerable<string> columns, IResourceFactory resourceFactory)
         {
-            return columns == null || !columns.Any() ? source : CallGenericSelectMethod(source, columns);
+            return columns == null || !columns.Any() ? source : CallGenericSelectMethod(source, columns, resourceFactory);
         }
 
         public static IOrderedQueryable<TSource> Sort<TSource>(this IQueryable<TSource> source, SortQueryContext sortQuery)
@@ -342,7 +342,7 @@ private static Expression CreateTupleAccessForConstantExpression(object value, T
             return Expression.Property(tupleCreateCall, "Item1");
         }
 
-        private static IQueryable<TSource> CallGenericSelectMethod<TSource>(IQueryable<TSource> source, IEnumerable<string> columns)
+        private static IQueryable<TSource> CallGenericSelectMethod<TSource>(IQueryable<TSource> source, IEnumerable<string> columns, IResourceFactory resourceFactory)
         {
             var sourceType = typeof(TSource);
             var parameter = Expression.Parameter(source.ElementType, "x");
@@ -386,7 +386,7 @@ private static IQueryable<TSource> CallGenericSelectMethod<TSource>(IQueryable<T
                         collectionElementType.GetProperty(prop), Expression.PropertyOrField(nestedParameter, prop))).ToList();
 
                     // { new Item() }
-                    var newNestedExp = Expression.New(collectionElementType);
+                    var newNestedExp = resourceFactory.CreateNewExpression(collectionElementType);
                     var initNestedExp = Expression.MemberInit(newNestedExp, nestedBindings);
                     // { y => new Item() {Id = y.Id, Name = y.Name}}
                     var body = Expression.Lambda(initNestedExp, nestedParameter);
@@ -419,7 +419,7 @@ private static IQueryable<TSource> CallGenericSelectMethod<TSource>(IQueryable<T
                         nestedBindings.Add(Expression.Bind(propInfo, nestedBody));
                     }
                     // { new Owner() }
-                    var newExp = Expression.New(nestedPropertyType);
+                    var newExp = resourceFactory.CreateNewExpression(nestedPropertyType);
                     // { new Owner() { Id = x.Owner.Id, Name = x.Owner.Name }}
                     var newInit = Expression.MemberInit(newExp, nestedBindings);
 
@@ -436,7 +436,8 @@ private static IQueryable<TSource> CallGenericSelectMethod<TSource>(IQueryable<T
                 nestedBindings.Clear();
             }
 
-            var sourceInit = Expression.MemberInit(Expression.New(sourceType), sourceBindings);
+            var newExpression = resourceFactory.CreateNewExpression(sourceType);
+            var sourceInit = Expression.MemberInit(newExpression, sourceBindings);
             var finalBody = Expression.Lambda(sourceInit, parameter);
 
             return source.Provider.CreateQuery<TSource>(Expression.Call(

src/JsonApiDotNetCore/Extensions/TypeExtensions.cs

@@ -71,9 +71,30 @@ public static bool IsOrImplementsInterface(this Type source, Type interfaceType)
 
         public static bool HasSingleConstructorWithoutParameters(this Type type)
         {
-            ConstructorInfo[] constructors = type.GetConstructors();
+            ConstructorInfo[] constructors = type.GetConstructors().Where(c => !c.IsStatic).ToArray();
 
             return constructors.Length == 1 && constructors[0].GetParameters().Length == 0;
         }
+
+        public static ConstructorInfo GetLongestConstructor(this Type type)
+        {
+            ConstructorInfo[] constructors = type.GetConstructors().Where(c => !c.IsStatic).ToArray();
+
+            ConstructorInfo bestMatch = constructors[0];
+            int maxParameterLength = constructors[0].GetParameters().Length;
+
+            for (int index = 1; index < constructors.Length; index++)
+            {
+                var constructor = constructors[index];
+                int length = constructor.GetParameters().Length;
+                if (length > maxParameterLength)
+                {
+                    bestMatch = constructor;
+                    maxParameterLength = length;
+                }
+            }
+
+            return bestMatch;
+        }
     }
 }

src/JsonApiDotNetCore/Internal/IResourceFactory.cs

@@ -1,4 +1,7 @@
 using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+using System.Reflection;
 using JsonApiDotNetCore.Extensions;
 using JsonApiDotNetCore.Models;
 using Microsoft.Extensions.DependencyInjection;
@@ -9,6 +12,7 @@ public interface IResourceFactory
     {
         public IIdentifiable CreateInstance(Type resourceType);
         public TResource CreateInstance<TResource>() where TResource : IIdentifiable;
+        public NewExpression CreateNewExpression(Type resourceType);
     }
 
     internal sealed class DefaultResourceFactory : IResourceFactory
@@ -53,5 +57,25 @@ private static object InnerCreateInstance(Type type, IServiceProvider servicePro
                     exception);
             }
         }
+
+        public NewExpression CreateNewExpression(Type resourceType)
+        {
+            if (resourceType.HasSingleConstructorWithoutParameters())
+            {
+                return Expression.New(resourceType);
+            }
+
+            List<Expression> constructorArguments = new List<Expression>();
+
+            var longestConstructor = resourceType.GetLongestConstructor();
+            foreach (ParameterInfo constructorParameter in longestConstructor.GetParameters())
+            {
+                var constructorArgument =
+                    ActivatorUtilities.CreateInstance(_serviceProvider, constructorParameter.ParameterType);
+                constructorArguments.Add(Expression.Constant(constructorArgument));
+            }
+
+            return Expression.New(longestConstructor, constructorArguments);
+        }
     }
 }

test/DiscoveryTests/ServiceDiscoveryFacadeTests.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Collections.Generic;
 using GettingStarted.Models;
 using GettingStarted.ResourceDefinitionExample;
@@ -41,14 +40,14 @@ public ServiceDiscoveryFacadeTests()
 
             _services.AddSingleton<IJsonApiOptions>(options);
             _services.AddSingleton<ILoggerFactory>(new LoggerFactory());
-            _services.AddScoped((_) => new Mock<ILinkBuilder>().Object);
-            _services.AddScoped((_) => new Mock<ICurrentRequest>().Object);
-            _services.AddScoped((_) => new Mock<ITargetedFields>().Object);
-            _services.AddScoped((_) => new Mock<IResourceGraph>().Object);
-            _services.AddScoped((_) => new Mock<IGenericServiceFactory>().Object);
-            _services.AddScoped((_) => new Mock<IResourceContextProvider>().Object);
+            _services.AddScoped(_ => new Mock<ILinkBuilder>().Object);
+            _services.AddScoped(_ => new Mock<ICurrentRequest>().Object);
+            _services.AddScoped(_ => new Mock<ITargetedFields>().Object);
+            _services.AddScoped(_ => new Mock<IResourceGraph>().Object);
+            _services.AddScoped(_ => new Mock<IGenericServiceFactory>().Object);
+            _services.AddScoped(_ => new Mock<IResourceContextProvider>().Object);
             _services.AddScoped(typeof(IResourceChangeTracker<>), typeof(DefaultResourceChangeTracker<>));
-            _services.AddScoped<IResourceFactory, FakeResourceFactory>();
+            _services.AddScoped(_ => new Mock<IResourceFactory>().Object);
 
             _resourceGraphBuilder = new ResourceGraphBuilder(options, NullLoggerFactory.Instance);
         }
@@ -132,22 +131,10 @@ public TestModelRepository(
                 ITargetedFields targetedFields,
                 IResourceGraph resourceGraph,
                 IGenericServiceFactory genericServiceFactory,
+                IResourceFactory resourceFactory,
                 ILoggerFactory loggerFactory)
-                : base(targetedFields, _dbContextResolver, resourceGraph, genericServiceFactory, loggerFactory)
+                : base(targetedFields, _dbContextResolver, resourceGraph, genericServiceFactory, resourceFactory, loggerFactory)
             { }
         }
-
-        public class FakeResourceFactory : IResourceFactory
-        {
-            public IIdentifiable CreateInstance(Type resourceType)
-            {
-                throw new NotImplementedException();
-            }
-
-            public TResource CreateInstance<TResource>() where TResource : IIdentifiable
-            {
-                throw new NotImplementedException();
-            }
-        }
     }
 }

test/IntegrationTests/Data/EntityRepositoryTests.cs

@@ -12,6 +12,8 @@
 using System.Threading.Tasks;
 using IntegrationTests;
 using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Internal;
+using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.Extensions.Logging.Abstractions;
 using Xunit;
 
@@ -161,11 +163,13 @@ public async Task Paging_PageNumberIsNegative_GiveBackReverseAmountOfIds(int pag
 
         private (DefaultResourceRepository<TodoItem> Repository, Mock<ITargetedFields> TargetedFields) Setup(AppDbContext context)
         {
+            var serviceProvider = ((IInfrastructure<IServiceProvider>) context).Instance;
+            var resourceFactory = new DefaultResourceFactory(serviceProvider);
             var contextResolverMock = new Mock<IDbContextResolver>();
             contextResolverMock.Setup(m => m.GetContext()).Returns(context);
             var resourceGraph = new ResourceGraphBuilder(new JsonApiOptions(), NullLoggerFactory.Instance).AddResource<TodoItem>().Build();
             var targetedFields = new Mock<ITargetedFields>();
-            var repository = new DefaultResourceRepository<TodoItem>(targetedFields.Object, contextResolverMock.Object, resourceGraph, null, NullLoggerFactory.Instance);
+            var repository = new DefaultResourceRepository<TodoItem>(targetedFields.Object, contextResolverMock.Object, resourceGraph, null, resourceFactory, NullLoggerFactory.Instance);
             return (repository, targetedFields);
         }