[client][managed][offline] insert should throw if the item already ex…

…ists #491

sdk/Managed/src/Microsoft.WindowsAzure.MobileServices/Table/Sync/MobileServiceSyncContext.cs

@@ -372,6 +372,10 @@ private Task ExecuteOperationAsync(MobileServiceTableOperation operation, JObjec
                 }
                 catch (Exception ex)
                 {
+                    if (ex is MobileServiceLocalStoreException)
+                    {
+                        throw;
+                    }
                     throw new MobileServiceLocalStoreException(Resources.SyncStore_OperationFailed, ex);
                 }
 

sdk/Managed/src/Microsoft.WindowsAzure.MobileServices/Table/Sync/Queue/Operations/InsertOperation.cs

@@ -61,9 +61,14 @@ public override void Collapse(MobileServiceTableOperation newOperation)
             }
         }
 
-        public override Task ExecuteLocalAsync(IMobileServiceLocalStore store, JObject item)
+        public override async Task ExecuteLocalAsync(IMobileServiceLocalStore store, JObject item)
         {
-            return store.UpsertAsync(this.TableName, item, fromServer: false);
+            if (await store.LookupAsync(this.TableName, this.ItemId) != null)
+            {
+                throw new MobileServiceLocalStoreException(Resources.SyncContext_DuplicateInsert, null);
+            }
+
+            await store.UpsertAsync(this.TableName, item, fromServer: false);
         }
     }
 }

sdk/Managed/test/Microsoft.WindowsAzure.MobileServices.SQLiteStore.Test/UnitTests/SQLiteStoreTests.Integration.cs

@@ -23,6 +23,33 @@ public class SQLiteStoreIntegrationTests : TestBase
 
         public static string TestDbName = SQLiteStoreTests.TestDbName;
 
+        [AsyncTestMethod]
+        public async Task InsertAsync_Throws_IfItemAlreadyExistsInLocalStore()
+        {
+            ResetDatabase(TestTable);
+
+            var store = new MobileServiceSQLiteStore(TestDbName);
+            store.DefineTable(TestTable, new JObject()
+            {
+                { "id", String.Empty},
+                { "String", String.Empty }
+            });
+
+            var hijack = new TestHttpHandler();
+            IMobileServiceClient service = await CreateClient(hijack, store);
+
+            string pullResult = "[{\"id\":\"abc\",\"String\":\"Wow\"}]";
+            hijack.AddResponseContent(pullResult);
+            hijack.AddResponseContent("[]");
+
+            IMobileServiceSyncTable table = service.GetSyncTable(TestTable);
+            await table.PullAsync(null, null);
+
+            var ex = await AssertEx.Throws<MobileServiceLocalStoreException>(() => table.InsertAsync(new JObject() { { "id", "abc" } }));
+
+            Assert.AreEqual(ex.Message, "An insert operation on the item is already in the queue.");
+        }
+
         [AsyncTestMethod]
         public async Task ReadAsync_RoundTripsDate()
         {