Validate schema classes for duplicates

CHANGELOG.md

@@ -5,6 +5,7 @@
 - Exposed `Realm.WriteCopy` API to copy a Realm file and optionally encrypt it with a different key. ([#1464](https://github.com/realm/realm-dotnet/pull/1464))
 - The runtime representations of all Realm collections (`IQueryable<T>` and `IList<T>`) now implement the `IList` interface that is needed for data-binding to `ListView` in UWP applications. ([#1469](https://github.com/realm/realm-dotnet/pull/1469))
 - Exposed `User.RetrieveInfoForUserAsync` API to allow admin users to lookup other users' identities in the Realm Object Server. This can be used, for example, to find a user by knowing their Facebook id. ([#1486](https://github.com/realm/realm-dotnet/pull/1486))
+- Added a check to verify there are no duplicate object names when creating the schema. ([#1502](https://github.com/realm/realm-dotnet/pull/1502))
 - Added more comprehensive error messages when passing an invalid url scheme to `SyncConfiguration` or `User.LoginAsync`. ([#1501](https://github.com/realm/realm-dotnet/pull/1501))
 
 ### Bug fixes

Realm/Realm/Schema/RealmSchema.cs

@@ -102,9 +102,19 @@ IEnumerator IEnumerable.GetEnumerator()
         internal static RealmSchema CreateSchemaForClasses(IEnumerable<Type> classes)
         {
             var builder = new Builder();
+            var classNames = new HashSet<string>();
             foreach (var @class in classes)
             {
-                builder.Add(ObjectSchema.FromType(@class));
+                var objectSchema = ObjectSchema.FromType(@class);
+                if (!classNames.Add(objectSchema.Name))
+                {
+                    var duplicateType = builder.Single(s => s.Name == objectSchema.Name).Type;
+                    var errorMessage = "The names (without namespace) of objects persisted in Realm must be unique." +
+                        $"The duplicate types are {@class.FullName} and {duplicateType.FullName}. Either rename one" +
+                        " of them or explicitly specify ObjectClasses on your RealmConfiguration.";
+                    throw new NotSupportedException(errorMessage);
+                }
+                builder.Add(objectSchema);
             }
 
             return builder.Build();

Tests/Tests.Shared/ConfigurationTests.cs

@@ -261,5 +261,42 @@ public void ReadOnlyRealmsArentWritable()
                 }, Throws.TypeOf<RealmInvalidTransactionException>());
             }
         }
+
+        [Test]
+        public void DuplicateClassNames_ThrowsException()
+        {
+            var config = new RealmConfiguration
+            {
+                ObjectClasses = new[]
+                {
+                    typeof(Foo.DuplicateClass),
+                    typeof(Bar.DuplicateClass)
+                }
+            };
+
+            var constraint = Throws.TypeOf<NotSupportedException>().And
+                                   .Message.Contains("Foo.DuplicateClass").And
+                                   .Message.Contains("Bar.DuplicateClass");
+
+            Assert.That(() => Realm.GetInstance(config), constraint);
+        }
+    }
+}
+
+namespace Foo
+{
+    [Explicit]
+    public class DuplicateClass : RealmObject
+    {
+        public int IntValue { get; set; }
+    }
+}
+
+namespace Bar
+{
+    [Explicit]
+    public class DuplicateClass : RealmObject
+    {
+        public string StringValue { get; set; }
     }
 }