Add support for subscription inclusions

Realm/Realm/Handles/SubscriptionHandle.cs

@@ -17,6 +17,7 @@
 ////////////////////////////////////////////////////////////////////////////
 
 using System;
+using System.Linq;
 using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 using Realms.Exceptions;
@@ -37,10 +38,10 @@ private static class NativeMethods
             [DllImport(InteropConfig.DLL_NAME, EntryPoint = "realm_subscription_create", CallingConvention = CallingConvention.Cdecl)]
             public static extern IntPtr subscribe(
                 ResultsHandle results,
-                [MarshalAs(UnmanagedType.LPWStr)] string name,
-                int name_len,
+                [MarshalAs(UnmanagedType.LPWStr)] string name, int name_len,
                 long time_to_live,
                 [MarshalAs(UnmanagedType.I1)] bool update,
+                [MarshalAs(UnmanagedType.LPArray), In] Native.StringValue[] inclusions, int inclusions_length,
                 out NativeException ex);
 
             [DllImport(InteropConfig.DLL_NAME, EntryPoint = "realm_subscription_get_state", CallingConvention = CallingConvention.Cdecl)]
@@ -64,10 +65,23 @@ private SubscriptionHandle(IntPtr handle) : base(null, handle)
         {
         }
 
-        public static SubscriptionHandle Create(ResultsHandle results, string name, long? timeToLive, bool update)
+        public static SubscriptionHandle Create(ResultsHandle results, string name, long? timeToLive, bool update, string[] inclusions)
         {
+            var nativeInclusions = new Native.StringValue[0];
+            if (inclusions != null)
+            {
+                nativeInclusions = inclusions.Select(i => new Native.StringValue { Value = i }).ToArray();
+            }
+
             // We use -1 to signal "no value"
-            var handle = NativeMethods.subscribe(results, name, name?.Length ?? -1, timeToLive ?? -1, update, out var ex);
+            var handle = NativeMethods.subscribe(
+                results,
+                name, name?.Length ?? -1,
+                timeToLive ?? -1,
+                update,
+                nativeInclusions, inclusions?.Length ?? -1,
+                out var ex);
+
             ex.ThrowIfNecessary();
 
             return new SubscriptionHandle(handle);

Realm/Realm/Helpers/LinqHelper.cs

@@ -0,0 +1,58 @@
+////////////////////////////////////////////////////////////////////////////
+//
+// Copyright 2018 Realm Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Reflection;
+
+namespace Realms.Helpers
+{
+    internal static class LinqHelper
+    {
+        public static string[] ToStringPaths<TSource, TProperty>(this Expression<Func<TSource, TProperty>>[] expressions)
+        {
+            return expressions.Select(ToStringPath).ToArray();
+        }
+
+        public static string ToStringPath<TSource, TResult>(this Expression<Func<TSource, TResult>> expression)
+        {
+            var visitor = new PropertyVisitor();
+            visitor.Visit(expression.Body);
+            visitor.Path.Reverse();
+            return string.Join(".", visitor.Path);
+        }
+
+        private class PropertyVisitor : ExpressionVisitor
+        {
+            public List<string> Path { get; } = new List<string>();
+
+            protected override Expression VisitMember(MemberExpression node)
+            {
+                if (!(node.Member is PropertyInfo))
+                {
+                    throw new ArgumentException("The path can only contain properties", nameof(node));
+                }
+
+                this.Path.Add(node.Member.Name);
+                return base.VisitMember(node);
+            }
+        }
+    }
+}

Realm/Realm/Native/StringValue.cs

@@ -0,0 +1,31 @@
+////////////////////////////////////////////////////////////////////////////
+//
+// Copyright 2016 Realm Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System.Runtime.InteropServices;
+
+namespace Realms.Sync.Native
+{
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct StringValue
+    {
+        internal static readonly int Size = Marshal.SizeOf<StringValue>();
+
+        [MarshalAs(UnmanagedType.LPStr)]
+        public string Value;
+    }
+}

Realm/Realm/Sync/Subscription.cs

@@ -20,6 +20,7 @@
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
+using System.Linq.Expressions;
 using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 using Realms.Exceptions;
@@ -85,6 +86,11 @@ public static Subscription<T> Subscribe<T>(this IQueryable<T> query, string name
         /// <param name="options">
         /// Options that configure some metadata of the subscription, such as its name or time to live.
         /// </param>
+        /// <param name="includedBacklinks">
+        /// An array of property expressions which specifies which linkingObjects relationships should be included in
+        /// the subscription. Subscriptions already include link and list properties (in the forward direction)
+        /// automatically by default.
+        /// </param>
         /// <returns>
         /// A <see cref="Subscription{T}"/> instance that contains information and methods for monitoring
         /// the state of the subscription.
@@ -93,17 +99,27 @@ public static Subscription<T> Subscribe<T>(this IQueryable<T> query, string name
         /// <exception cref="ArgumentException">
         /// Thrown if the <c>query</c> was not obtained from a query-based synchronized Realm.
         /// </exception>
-        public static Subscription<T> Subscribe<T>(this IQueryable<T> query, SubscriptionOptions options = null)
+        public static Subscription<T> Subscribe<T>(
+            this IQueryable<T> query,
+            SubscriptionOptions options = null,
+            params Expression<Func<T, IQueryable>>[] includedBacklinks)
         {
             Argument.NotNull(query, nameof(query));
 
             var results = query as RealmResults<T>;
             Argument.Ensure(results != null, $"{nameof(query)} must be an instance of IRealmCollection<{typeof(T).Name}>.", nameof(query));
 
+            options = options ?? new SubscriptionOptions();
+
             var syncConfig = results.Realm.Config as SyncConfigurationBase;
             Argument.Ensure(syncConfig?.IsFullSync == false, $"{nameof(query)} must be obtained from a synchronized Realm using query-based synchronization.", nameof(query));
 
-            var handle = SubscriptionHandle.Create(results.ResultsHandle, options.Name, (long?)options.TimeToLive?.TotalMilliseconds, options.ShouldUpdate);
+            var handle = SubscriptionHandle.Create(
+                results.ResultsHandle,
+                options.Name,
+                (long?)options.TimeToLive?.TotalMilliseconds,
+                options.ShouldUpdate,
+                includedBacklinks.ToStringPaths());
             return new Subscription<T>(handle, results);
         }
 
@@ -122,7 +138,7 @@ public static IRealmCollection<NamedSubscription> GetAllSubscriptions(this Realm
         }
 
         /// <summary>
-        /// Cancel a named subscription that was created by calling <see cref="Subscribe{T}(IQueryable{T}, SubscriptionOptions)"/>.
+        /// Cancel a named subscription that was created by calling <see cref="Subscribe{T}(IQueryable{T}, SubscriptionOptions, Expression{Func{T, IQueryable}}[])"/>.
         /// <para />
         /// Removing a subscription will delete all objects from the local Realm that were matched
         /// only by that subscription and not any remaining subscriptions. The deletion is performed
@@ -161,7 +177,7 @@ public static Task UnsubscribeAsync(this Realm realm, string subscriptionName)
         }
 
         /// <summary>
-        /// Cancel a subscription that was created by calling <see cref="Subscribe{T}(IQueryable{T}, SubscriptionOptions)"/>.
+        /// Cancel a subscription that was created by calling <see cref="Subscribe{T}(IQueryable{T}, SubscriptionOptions, Expression{Func{T, IQueryable}}[])"/>.
         /// <para />
         /// Removing a subscription will delete all objects from the local Realm that were matched
         /// only by that subscription and not any remaining subscriptions. The deletion is performed
@@ -229,7 +245,7 @@ private static void SubscriptionCallbackImpl(IntPtr managedHandle)
     /// <para/>
     /// The state of the subscription can be observed by subscribing to the <see cref="PropertyChanged"/> event handler.
     /// <para/>
-    /// Subscriptions are created by calling <see cref="Subscription.Subscribe{T}(IQueryable{T}, SubscriptionOptions)"/>.
+    /// Subscriptions are created by calling <see cref="Subscription.Subscribe{T}(IQueryable{T}, SubscriptionOptions, Expression{Func{T, IQueryable}}[])"/>.
     /// </summary>
     /// <typeparam name="T">The type of the objects that make up the subscription query.</typeparam>
     [SuppressMessage("StyleCop.CSharp.MaintainabilityRules", "SA1402:FileMayOnlyContainASingleClass")]

Tests/Realm.Tests/Sync/QueryBasedSyncTests.cs

@@ -229,8 +229,7 @@ public void Subscribe_UpdatesQuery(bool openAsync)
                     var updatedSub = realm.All<ObjectA>()
                                           .Where(o => o.IntValue < 3)
                                           .Subscribe(new SubscriptionOptions { Name = "foo", ShouldUpdate = true });
-
-
+
                     await updatedSub.WaitForSynchronizationAsync().Timeout(2000);
                     Assert.That(subscription.Results.Count(), Is.EqualTo(3));
 
@@ -271,7 +270,7 @@ public void Subscribe_UpdatesTtl(bool openAsync, bool changeTtlValue)
                     var updatedSub = realm.All<ObjectA>()
                                           .Where(o => o.IntValue < 5)
                                           .Subscribe(new SubscriptionOptions { Name = "foo", ShouldUpdate = true, TimeToLive = updatedTtl });
-                                          
+
                     await updatedSub.WaitForSynchronizationAsync().Timeout(2000);
 
                     // NamedSub is a Realm object so it should have updated itself.
@@ -455,12 +454,55 @@ await Task.Run(() =>
             });
         }
 
+        [TestCase(true)]
+        [TestCase(false)]
+        public void Subscribe_WithInclusions(bool openAsync)
+        {
+            SyncTestHelpers.RunRosTestAsync(async () =>
+            {
+                using (var realm = await GetQueryBasedRealm(openAsync))
+                {
+                    var subscription = realm.All<ObjectB>()
+                                            .Where(b => b.BoolValue)
+                                            .Subscribe(includedBacklinks: b => b.As);
+
+                    await subscription.WaitForSynchronizationAsync().Timeout(2000);
+
+                    Assert.That(realm.All<ObjectB>().Count(), Is.EqualTo(5));
+                    Assert.That(realm.All<ObjectA>().Count(), Is.EqualTo(5));
+                    Assert.That(realm.All<ObjectA>().ToArray().All(a => a.IntValue % 2 == 0));
+                }
+            });
+        }
+
+        [TestCase(true)]
+        [TestCase(false)]
+        public void Subscribe_WithInclusions_ExtraHop(bool openAsync)
+        {
+            SyncTestHelpers.RunRosTestAsync(async () =>
+            {
+                using (var realm = await GetQueryBasedRealm(openAsync))
+                {
+                    var subscription = realm.All<ObjectC>()
+                                            .Filter("B.BoolValue == true")
+                                            .Subscribe(includedBacklinks: c => c.B.As);
+
+                    await subscription.WaitForSynchronizationAsync().Timeout(2000);
+
+                    Assert.That(realm.All<ObjectC>().Count(), Is.EqualTo(5));
+                    Assert.That(realm.All<ObjectB>().Count(), Is.EqualTo(5));
+                    Assert.That(realm.All<ObjectA>().Count(), Is.EqualTo(5));
+                    Assert.That(realm.All<ObjectA>().ToArray().All(a => a.IntValue % 2 == 0));
+                }
+            });
+        }
+
         private async Task<Realm> GetQueryBasedRealm(bool openAsync, [CallerMemberName] string realmPath = null)
         {
             var user = await SyncTestHelpers.GetUserAsync();
             var config = new QueryBasedSyncConfiguration(SyncTestHelpers.RealmUri($"~/{realmPath}_{openAsync}"), user, Guid.NewGuid().ToString())
             {
-                ObjectClasses = new[] { typeof(ObjectA), typeof(ObjectB) }
+                ObjectClasses = new[] { typeof(ObjectA), typeof(ObjectB), typeof(ObjectC) }
             };
 
             using (var original = GetRealm(config))
@@ -469,7 +511,7 @@ private async Task<Realm> GetQueryBasedRealm(bool openAsync, [CallerMemberName]
                 {
                     for (var i = 0; i < 10; i++)
                     {
-                        original.Add(new ObjectA
+                        var a = original.Add(new ObjectA
                         {
                             StringValue = "A #" + i,
                             IntValue = i,
@@ -479,6 +521,12 @@ private async Task<Realm> GetQueryBasedRealm(bool openAsync, [CallerMemberName]
                                 BoolValue = i % 2 == 0,
                             }
                         });
+
+                        original.Add(new ObjectC
+                        {
+                            IntValue = i,
+                            B = a.B
+                        });
                     }
                 });
 
@@ -522,6 +570,16 @@ public class ObjectB : RealmObject
             public string StringValue { get; set; }
 
             public bool BoolValue { get; set; }
+
+            [Backlink(nameof(ObjectA.B))]
+            public IQueryable<ObjectA> As { get; }
+        }
+
+        public class ObjectC : RealmObject
+        {
+            public int IntValue { get; set; }
+
+            public ObjectB B { get; set; }
         }
     }
 }

wrappers/src/marshalling.hpp

@@ -42,6 +42,11 @@ struct PrimitiveValue
     } value;
 };
 
+struct StringValue
+{
+    const char* value;
+};
+
 template<typename Collection>
 void collection_get_primitive(Collection* collection, size_t ndx, PrimitiveValue& value, NativeException::Marshallable& ex)
 {

wrappers/src/results_cs.cpp

@@ -26,6 +26,7 @@
 #include "notifications_cs.hpp"
 #include "wrapper_exceptions.hpp"
 #include "timestamp_helpers.hpp"
+#include "schema_cs.hpp"
 #include <realm/parser/parser.hpp>
 #include <realm/parser/query_builder.hpp>
 
@@ -44,22 +45,6 @@ inline T get(Results* results, size_t ndx, NativeException::Marshallable& ex)
     });
 }
 
-inline void alias_backlinks(parser::KeyPathMapping &mapping, const realm::SharedRealm &realm)
-{
-    const realm::Schema &schema = realm->schema();
-    for (auto it = schema.begin(); it != schema.end(); ++it) {
-        for (const Property &property : it->computed_properties) {
-            if (property.type == realm::PropertyType::LinkingObjects) {
-                auto target_object_schema = schema.find(property.object_type);
-                const TableRef table = ObjectStore::table_for_object_type(realm->read_group(), it->name);
-                const TableRef target_table = ObjectStore::table_for_object_type(realm->read_group(), target_object_schema->name);
-                std::string native_name = "@links." + std::string(target_table->get_name()) + "." + property.link_origin_property_name;
-                mapping.add_mapping(table, property.name, native_name);
-            }
-        }
-    }
-}
-
 extern "C" {
 
 REALM_EXPORT void results_destroy(Results* results_ptr)