From 7e706db22ac2f22953be478af5d99d897fc2787d Mon Sep 17 00:00:00 2001
From: Nikola Irinchev <irinchev@me.com>
Date: Fri, 4 Aug 2017 15:59:36 +0300
Subject: [PATCH] Validate schema classes for duplicates

---
 CHANGELOG.md                             |  1 +
 Realm/Realm/Schema/RealmSchema.cs        | 12 +++++++-
 Tests/Tests.Shared/ConfigurationTests.cs | 37 ++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a38de11245..9bb2e337c7 100644
--- a/CHANGELOG.md
+++ b/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))
 
 ### Bug fixes
 - Fix an exception being thrown when comparing non-constant character value in a query. ([#1471](https://github.com/realm/realm-dotnet/pull/1471))
diff --git a/Realm/Realm/Schema/RealmSchema.cs b/Realm/Realm/Schema/RealmSchema.cs
index 5fea5af2d3..4aec13a4fb 100644
--- a/Realm/Realm/Schema/RealmSchema.cs
+++ b/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();
diff --git a/Tests/Tests.Shared/ConfigurationTests.cs b/Tests/Tests.Shared/ConfigurationTests.cs
index e4415ca65a..78014cdf43 100644
--- a/Tests/Tests.Shared/ConfigurationTests.cs
+++ b/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; }
     }
 }
\ No newline at end of file