support for data migrations

src/js_realm.hpp

@@ -243,11 +243,12 @@ inline typename T::Function Realm<T>::create_constructor(ContextType ctx) {
 }
 
 template<typename T>
-void Realm<T>::constructor(ContextType ctx, ObjectType this_object, size_t argc, const ValueType arguments[]) {
+void Realm<T>::constructor(ContextType ctx, ObjectType this_object, size_t argc, const ValueType arguments[]) {    
     static const String path_string = "path";
     static const String schema_string = "schema";
     static const String schema_version_string = "schemaVersion";
     static const String encryption_key_string = "encryptionKey";
+    static const String migration_string = "migration";
 
     realm::Realm::Config config;
     typename Schema<T>::ObjectDefaultsMap defaults;
@@ -286,6 +287,18 @@ void Realm<T>::constructor(ContextType ctx, ObjectType this_object, size_t argc,
                 config.schema_version = 0;
             }
             
+            ValueType migration_value = Object::get_property(ctx, object, migration_string);
+            if (!Value::is_undefined(ctx, migration_value)) {
+                FunctionType migration_function = Value::validated_to_function(ctx, migration_value);
+                config.migration_function = [=](SharedRealm old_realm, SharedRealm realm) {
+                    ValueType arguments[2] = {
+                        create_object<T, RealmClass<T>>(ctx, new SharedRealm(old_realm)),
+                        create_object<T, RealmClass<T>>(ctx, new SharedRealm(realm))
+                    };
+                    Function<T>::call(ctx, migration_function, nullptr, 2, arguments);
+                };
+            }
+            
             ValueType encryption_key_value = Object::get_property(ctx, object, encryption_key_string);
             if (!Value::is_undefined(ctx, encryption_key_value)) {
                 std::string encryption_key = NativeAccessor::to_binary(ctx, encryption_key_value);

src/js_realm_object.hpp

@@ -80,7 +80,7 @@ typename T::Object RealmObject<T>::create_instance(ContextType ctx, realm::Objec
     auto name = realm_object.get_object_schema().name;
     auto object = create_object<T, RealmObjectClass<T>>(ctx, new realm::Object(realm_object));
 
-    if (!delegate->m_constructors.count(name)) {
+    if (!delegate || !delegate->m_constructors.count(name)) {
         return object;
     }
 

tests/js/asserts.js

@@ -87,6 +87,23 @@ module.exports = {
         }
     },
 
+    assertThrowsException: function(func, expectedException) {
+        var caught = false;
+        try {
+            func();
+        }
+        catch (e) {
+            caught = true;
+            if (e != expectedException) {
+                throw new TestFailureError('Expected exception "' + expectedException + '" not thrown - instead caught: "' + e + '"');
+            }
+        }
+
+        if (!caught) {
+            throw new TestFailureError('Expected exception not thrown');
+        }
+    },
+
     assertTrue: function(condition, errorMessage) {
         if (!condition) {
             throw new TestFailureError(errorMessage || 'Condition expected to be true');

tests/js/index.js

@@ -25,6 +25,7 @@ var TESTS = {
     ResultsTests: require('./results-tests'),
     QueryTests: require('./query-tests'),
     EncryptionTests: require('./encryption-tests'),
+    MigrationTests: require('./migration-tests'),
 };
 
 var SPECIAL_METHODS = {

tests/js/migration-tests.js

@@ -0,0 +1,118 @@
+////////////////////////////////////////////////////////////////////////////
+//
+// 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.
+//
+////////////////////////////////////////////////////////////////////////////
+
+'use strict';
+
+var Realm = require('realm');
+var BaseTest = require('./base-test');
+var TestCase = require('./asserts');
+var Schemas = require('./schemas');
+
+module.exports = BaseTest.extend({
+    testMigrationFunction: function() {
+        var count = 0;
+        function migrationFunction(oldRealm, newRealm) {
+            TestCase.assertEqual(oldRealm.schemaVersion, 0);
+            TestCase.assertEqual(newRealm.schemaVersion, 1);
+            count++;
+        }
+
+        // no migration should be run
+        var realm = new Realm({schema: [], migration: migrationFunction});
+        TestCase.assertEqual(0, count);
+        realm.close();
+
+        // migration should be run
+        realm = new Realm({schema: [Schemas.TestObject], migration: migrationFunction, schemaVersion: 1});
+        TestCase.assertEqual(1, count);
+        realm.close();
+
+        // invalid migration function
+        TestCase.assertThrows(function() {
+            new Realm({schema: [], schemaVersion: 2, migration: 'invalid'});
+        });
+
+        // migration function exceptions should propogate
+        var exception = 'expected exception';
+        realm = undefined;
+        TestCase.assertThrowsException(function() {
+            realm = new Realm({schema: [], schemaVersion: 3, migration: function() {
+                throw exception;
+            }});
+        }, exception);
+        TestCase.assertEqual(realm, undefined);
+        TestCase.assertEqual(Realm.schemaVersion(Realm.defaultPath), 1);
+
+        // migration function shouldn't run if nothing changes
+        realm = new Realm({schema: [Schemas.TestObject], migration: migrationFunction, schemaVersion: 1});
+        TestCase.assertEqual(1, count);
+        realm.close();
+
+        // migration function should run if only schemaVersion changes
+        realm = new Realm({schema: [Schemas.TestObject], migration: function() { count++; }, schemaVersion: 2});
+        TestCase.assertEqual(2, count);
+        realm.close();
+    },
+
+    testDataMigration: function() {
+        var realm = new Realm({schema: [{
+            name: 'TestObject',
+            properties: {
+                prop0: 'string',
+                prop1: 'int',
+            }
+        }]});
+        realm.write(function() {
+            realm.create('TestObject', ['stringValue', 1]);
+        });
+        realm.close();
+
+        var realm = new Realm({
+            schema: [{
+                name: 'TestObject',
+                properties: {
+                    renamed: 'string',
+                    prop1: 'int',
+                }
+            }], 
+            schemaVersion: 1, 
+            migration: function(oldRealm, newRealm) {
+                var oldObjects = oldRealm.objects('TestObject');
+                var newObjects = newRealm.objects('TestObject');
+                TestCase.assertEqual(oldObjects.length, 1);
+                TestCase.assertEqual(newObjects.length, 1);
+
+                TestCase.assertEqual(oldObjects[0].prop0, 'stringValue');
+                TestCase.assertEqual(oldObjects[0].prop1, 1);
+                //TestCase.assertThrows(function() { oldObjects[0].renamed; });
+
+                //TestCase.assertThrows(function() { newObjects[0].prop0; });
+                TestCase.assertEqual(newObjects[0].renamed, '');
+                TestCase.assertEqual(newObjects[0].prop1, 1);
+
+                newObjects[0].renamed = oldObjects[0].prop0;
+            }
+        });
+
+        var objects = realm.objects('TestObject');
+        TestCase.assertEqual(objects.length, 1);
+        TestCase.assertEqual(objects[0].renamed, 'stringValue');
+        TestCase.assertEqual(objects[0].prop1, 1);
+        TestCase.assertThrows(function() { newObjects[0].prop0; });
+    },
+});