Add example projects and tests

src/JsonApiDotNetCore.MongoDb/Errors/UnsupportedComparisonExpressionException.cs

@@ -0,0 +1,17 @@
+using System.Net;
+using JsonApiDotNetCore.Errors;
+using JsonApiDotNetCore.Serialization.Objects;
+
+namespace JsonApiDotNetCore.MongoDb.Errors
+{
+    public sealed class UnsupportedComparisonExpressionException : JsonApiException
+    {
+        public UnsupportedComparisonExpressionException()
+            : base(new Error(HttpStatusCode.BadRequest)
+            {
+                Title = "Comparing attributes against each other is not supported when using MongoDB."
+            })
+        {
+        }
+    }
+}

src/JsonApiDotNetCore.MongoDb/Errors/UnsupportedRelationshipException.cs

@@ -0,0 +1,17 @@
+using System.Net;
+using JsonApiDotNetCore.Errors;
+using JsonApiDotNetCore.Serialization.Objects;
+
+namespace JsonApiDotNetCore.MongoDb.Errors
+{
+    public sealed class UnsupportedRelationshipException : JsonApiException
+    {
+        public UnsupportedRelationshipException()
+            : base(new Error(HttpStatusCode.BadRequest)
+            {
+                Title = "Relationships are not supported when using MongoDB."
+            })
+        {
+        }
+    }
+}

src/JsonApiDotNetCore.MongoDb/Internal/MongoDbModel.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using JsonApiDotNetCore.Configuration;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata;
+
+namespace JsonApiDotNetCore.MongoDb.Internal
+{
+    internal sealed class MongoDbModel : IModel
+    {
+        private readonly IResourceContextProvider _resourceContextProvider;
+
+        public object this[string name] => throw new NotImplementedException();
+
+        public MongoDbModel(IResourceContextProvider resourceContextProvider)
+        {
+            _resourceContextProvider = resourceContextProvider ?? throw new ArgumentNullException(nameof(resourceContextProvider));
+        }
+
+        public IEnumerable<IEntityType> GetEntityTypes()
+        {
+            var resourceContexts = _resourceContextProvider.GetResourceContexts();
+            return resourceContexts.Select(resourceContext => new MongoEntityType(resourceContext, this));
+        }
+
+        public IAnnotation FindAnnotation(string name) => throw new NotImplementedException();
+        public IEnumerable<IAnnotation> GetAnnotations() => throw new NotImplementedException();
+        public IEntityType FindEntityType(string name) => throw new NotImplementedException();
+        public IEntityType FindEntityType(string name, string definingNavigationName, IEntityType definingEntityType) => throw new NotImplementedException();
+    }
+}

src/JsonApiDotNetCore.MongoDb/Internal/MongoDbProperty.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata;
+
+namespace JsonApiDotNetCore.MongoDb.Internal
+{
+    internal sealed class MongoDbProperty : IProperty
+    {
+        public IEntityType DeclaringEntityType { get; }
+        public PropertyInfo PropertyInfo { get; }
+
+        public string Name => throw new NotImplementedException();
+        public Type ClrType => throw new NotImplementedException();
+        public FieldInfo FieldInfo => throw new NotImplementedException();
+        public ITypeBase DeclaringType => throw new NotImplementedException();
+        public bool IsNullable => throw new NotImplementedException();
+        public ValueGenerated ValueGenerated => throw new NotImplementedException();
+        public bool IsConcurrencyToken => throw new NotImplementedException();
+        public object this[string name] => throw new NotImplementedException();
+
+        public MongoDbProperty(PropertyInfo propertyInfo, MongoEntityType owner)
+        {
+            DeclaringEntityType = owner ?? throw new ArgumentNullException(nameof(owner));
+            PropertyInfo = propertyInfo ?? throw new ArgumentNullException(nameof(propertyInfo));
+        }
+
+        public IAnnotation FindAnnotation(string name) => throw new NotImplementedException();
+        public IEnumerable<IAnnotation> GetAnnotations() => throw new NotImplementedException();
+    }
+}

src/JsonApiDotNetCore.MongoDb/Internal/MongoEntityType.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using JsonApiDotNetCore.Configuration;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata;
+
+namespace JsonApiDotNetCore.MongoDb.Internal
+{
+    internal sealed class MongoEntityType : IEntityType
+    {
+        private readonly ResourceContext _resourceContext;
+
+        public IModel Model { get; }
+        public Type ClrType => _resourceContext.ResourceType;
+
+        public string Name => throw new NotImplementedException();
+        public IEntityType BaseType => throw new NotImplementedException();
+        public string DefiningNavigationName => throw new NotImplementedException();
+        public IEntityType DefiningEntityType => throw new NotImplementedException();
+        public object this[string name] => throw new NotImplementedException();
+
+        public MongoEntityType(ResourceContext resourceContext, MongoDbModel owner)
+        {
+            _resourceContext = resourceContext ?? throw new ArgumentNullException(nameof(resourceContext));
+            Model = owner ?? throw new ArgumentNullException(nameof(owner));
+        }
+
+        public IEnumerable<IProperty> GetProperties()
+        {
+            return _resourceContext.Attributes.Select(attr => new MongoDbProperty(attr.Property, this));
+        }
+
+        public IAnnotation FindAnnotation(string name) => throw new NotImplementedException();
+        public IEnumerable<IAnnotation> GetAnnotations() => throw new NotImplementedException();
+        public IKey FindPrimaryKey() => throw new NotImplementedException();
+        public IKey FindKey(IReadOnlyList<IProperty> properties) => throw new NotImplementedException();
+        public IEnumerable<IKey> GetKeys() => throw new NotImplementedException();
+        public IForeignKey FindForeignKey(IReadOnlyList<IProperty> properties, IKey principalKey, IEntityType principalEntityType) => throw new NotImplementedException();
+        public IEnumerable<IForeignKey> GetForeignKeys() => throw new NotImplementedException();
+        public IIndex FindIndex(IReadOnlyList<IProperty> properties) => throw new NotImplementedException();
+        public IEnumerable<IIndex> GetIndexes() => throw new NotImplementedException();
+        public IProperty FindProperty(string name) => throw new NotImplementedException();
+        public IServiceProperty FindServiceProperty(string name) => throw new NotImplementedException();
+        public IEnumerable<IServiceProperty> GetServiceProperties() => throw new NotImplementedException();
+    }
+}

src/JsonApiDotNetCore.MongoDb/MongoDbRepository.cs

@@ -1,21 +1,19 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Net;
 using System.Threading;
 using System.Threading.Tasks;
 using JsonApiDotNetCore.Configuration;
-using JsonApiDotNetCore.Errors;
+using JsonApiDotNetCore.MongoDb.Errors;
+using JsonApiDotNetCore.MongoDb.Internal;
+using JsonApiDotNetCore.MongoDb.Queries.Expressions;
 using JsonApiDotNetCore.Queries.Internal.QueryableBuilding;
 using JsonApiDotNetCore.Repositories;
 using JsonApiDotNetCore.Resources;
 using MongoDB.Driver;
 using MongoDB.Driver.Linq;
 using JsonApiDotNetCore.Queries;
 using JsonApiDotNetCore.Queries.Expressions;
-using JsonApiDotNetCore.Serialization.Objects;
-using Microsoft.EntityFrameworkCore.Metadata;
-using Microsoft.EntityFrameworkCore.Infrastructure;
 
 namespace JsonApiDotNetCore.MongoDb
 {
@@ -30,7 +28,7 @@ public class MongoDbRepository<TResource, TId>
         private readonly ITargetedFields _targetedFields;
         private readonly IResourceContextProvider _resourceContextProvider;
         private readonly IResourceFactory _resourceFactory;
-        
+
         public MongoDbRepository(
             IMongoDatabase mongoDatabase,
             ITargetedFields targetedFields,
@@ -50,20 +48,12 @@ public virtual async Task<IReadOnlyCollection<TResource>> GetAsync(QueryLayer la
             CancellationToken cancellationToken)
         {
             if (layer == null) throw new ArgumentNullException(nameof(layer));
+
+            var queryExpressionValidator = new MongoDbQueryExpressionValidator();
+            queryExpressionValidator.Validate(layer);
 
-            try
-            {
-                var resources = await ApplyQueryLayer(layer).ToListAsync(cancellationToken);
-                return resources.AsReadOnly();
-            }
-            catch (ArgumentException e)
-            {
-                throw new JsonApiException(new Error(HttpStatusCode.BadRequest)
-                {
-                    Title = "MongoDB does not allow comparing two fields to each other, only constants.",
-                    Detail = e.Message
-                });
-            }
+            var resources = await ApplyQueryLayer(layer).ToListAsync(cancellationToken);
+            return resources.AsReadOnly();
         }
 
         /// <inheritdoc />
@@ -82,7 +72,9 @@ public virtual Task<int> CountAsync(FilterExpression topFilter, CancellationToke
         protected virtual IMongoQueryable<TResource> ApplyQueryLayer(QueryLayer layer)
         {
             if (layer == null) throw new ArgumentNullException(nameof(layer));
-            AssertNoInclude(layer);
+
+            var queryExpressionValidator = new MongoDbQueryExpressionValidator();
+            queryExpressionValidator.Validate(layer);
 
             var source = GetAll();
 
@@ -94,26 +86,11 @@ protected virtual IMongoQueryable<TResource> ApplyQueryLayer(QueryLayer layer)
                 nameFactory,
                 _resourceFactory,
                 _resourceContextProvider,
-                DummyModel.Instance);
+                new MongoDbModel(_resourceContextProvider));
 
             var expression = builder.ApplyQuery(layer);
             return (IMongoQueryable<TResource>)source.Provider.CreateQuery<TResource>(expression);
         }
-
-        private void AssertNoInclude(QueryLayer layer)
-        {
-            if (layer.Include != null && layer.Include.Elements.Count > 0)
-            {
-                throw new JsonApiException(new Error(HttpStatusCode.BadRequest)
-                {
-                    Title = "Relationships are not supported when using MongoDB.",
-                    Source = new ErrorSource
-                    {
-                        Parameter = "include"
-                    }
-                });
-            }
-        }
 
         protected virtual IQueryable<TResource> GetAll()
         {
@@ -153,10 +130,7 @@ private void AssertNoRelationship(TResource resourceFromRequest)
                 var rightResources = relationship.GetValue(resourceFromRequest);
                 if (rightResources != null)
                 {
-                    throw new JsonApiException(new Error(HttpStatusCode.BadRequest)
-                    {
-                        Title = "Relationships are not supported when using MongoDB."
-                    });
+                    throw new UnsupportedRelationshipException();
                 }
             }
         }
@@ -174,6 +148,8 @@ public virtual async Task UpdateAsync(TResource resourceFromRequest, TResource r
             if (resourceFromRequest == null) throw new ArgumentNullException(nameof(resourceFromRequest));
             if (resourceFromDatabase == null) throw new ArgumentNullException(nameof(resourceFromDatabase));
 
+            AssertNoRelationship(resourceFromRequest);
+
             foreach (var attr in _targetedFields.Attributes)
                 attr.SetValue(resourceFromDatabase, attr.GetValue(resourceFromRequest));
 
@@ -239,40 +215,4 @@ public MongoDbRepository(
         {
         }
     }
-
-    internal sealed class DummyModel : IModel
-    {
-        public static IModel Instance { get; } = new DummyModel();
-
-        public object this[string name] => throw new NotImplementedException();
-
-        private DummyModel()
-        {
-        }
-
-        public IAnnotation FindAnnotation(string name)
-        {
-            throw new NotImplementedException();
-        }
-
-        public IEnumerable<IAnnotation> GetAnnotations()
-        {
-            throw new NotImplementedException();
-        }
-
-        public IEnumerable<IEntityType> GetEntityTypes()
-        {
-            throw new NotImplementedException();
-        }
-
-        public IEntityType FindEntityType(string name)
-        {
-            throw new NotImplementedException();
-        }
-
-        public IEntityType FindEntityType(string name, string definingNavigationName, IEntityType definingEntityType)
-        {
-            throw new NotImplementedException();
-        }
-    }
 }

src/JsonApiDotNetCore.MongoDb/Queries/Expressions/MongoDbQueryExpressionValidator.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Linq;
+using System.Net;
+using JsonApiDotNetCore.Errors;
+using JsonApiDotNetCore.MongoDb.Errors;
+using JsonApiDotNetCore.Queries;
+using JsonApiDotNetCore.Queries.Expressions;
+using JsonApiDotNetCore.Resources.Annotations;
+using JsonApiDotNetCore.Serialization.Objects;
+
+namespace JsonApiDotNetCore.MongoDb.Queries.Expressions
+{
+    internal sealed class MongoDbQueryExpressionValidator : QueryExpressionRewriter<object>
+    {
+        public void Validate(QueryLayer layer)
+        {
+            if (layer == null) throw new ArgumentNullException(nameof(layer));
+
+            bool hasIncludes = layer.Include?.Elements.Any() == true;
+            var hasSparseRelationshipSets = layer.Projection?.Any(pair => pair.Key is RelationshipAttribute) == true;
+
+            if (hasIncludes || hasSparseRelationshipSets)
+            {
+                throw new UnsupportedRelationshipException();
+            }
+
+            ValidateExpression(layer.Filter);
+            ValidateExpression(layer.Sort);
+            ValidateExpression(layer.Pagination);
+        }
+
+        private void ValidateExpression(QueryExpression expression)
+        {
+            if (expression != null)
+            {
+                Visit(expression, null);
+            }
+        }
+
+        public override QueryExpression VisitResourceFieldChain(ResourceFieldChainExpression expression, object argument)
+        {
+            if (expression != null)
+            {
+                if (expression.Fields.Count > 1 || expression.Fields.First() is RelationshipAttribute)
+                {
+                    throw new UnsupportedRelationshipException();
+                }
+            }
+
+            return base.VisitResourceFieldChain(expression, argument);
+        }
+
+        public override QueryExpression VisitComparison(ComparisonExpression expression, object argument)
+        {
+            if (expression?.Left is ResourceFieldChainExpression && expression.Right is ResourceFieldChainExpression)
+            {
+                // https://jira.mongodb.org/browse/CSHARP-1592
+                throw new UnsupportedComparisonExpressionException();
+            }
+
+            return base.VisitComparison(expression, argument);
+        }
+    }
+}