Add 'deleteRealmIfMigrationNeeded' to configuration to delete a Realm if migration needed (#502)

CHANGELOG.md

@@ -5,6 +5,7 @@ X.Y.Z Release notes
 
 ### Enhancements
 * Added aggregate functions `min()`, `max()`, `sum()`, and `avg()` to `Realm.Results` and `Realm.List` (#807).
+* Added `deleteRealmIfMigrationNeeded` to configuration to delete a Realm if migration needed (#502).
 
 ### Bug fixes
 * Fixed port conflict between RN >= 0.48 inspector proxy and RPC server used for Chrome debugging (#1294).

docs/realm.js

@@ -296,6 +296,8 @@ Realm.defaultPath;
  *   - `validate_ssl` - Indicating if SSL certificates must be validated
  *   - `ssl_trust_certificate_path` - A path where to find trusted SSL certificates
  * The `error` callback can take up to four optional arguments: `message`, `isFatal`, `category`, and `code`.
+ * @property {boolean} [deleteRealmIfMigrationNeeded=false] - Specifies if this Realm should be deleted 
+ * if a migration is needed.
  */
 
 /**

lib/index.d.ts

@@ -84,6 +84,7 @@ declare namespace Realm {
         schema?: ObjectClass[] | ObjectSchema[];
         schemaVersion?: number;
         sync?: Realm.Sync.SyncConfiguration;
+        deleteRealmIfMigrationNeeded?: boolean;
     }
 
     // object props type

src/js_realm.hpp

@@ -394,6 +394,16 @@ void RealmClass<T>::constructor(ContextType ctx, ObjectType this_object, size_t
                 config.schema_mode = SchemaMode::ReadOnly;
             }
 
+            static const String delete_realm_if_migration_needed_string = "deleteRealmIfMigrationNeeded";
+            ValueType delete_realm_if_migration_needed_value = Object::get_property(ctx, object, delete_realm_if_migration_needed_string);
+            if (!Value::is_undefined(ctx, delete_realm_if_migration_needed_value) && Value::validated_to_boolean(ctx, delete_realm_if_migration_needed_value, "deleteRealmIfMigrationNeeded")) {
+                if (config.schema_mode == SchemaMode::ReadOnly) {
+                    throw std::invalid_argument("Cannot set 'deleteRealmIfMigrationNeeded' when 'readOnly' is set.");
+                }
+
+                config.schema_mode = SchemaMode::ResetFile;
+            }
+
             static const String schema_string = "schema";
             ValueType schema_value = Object::get_property(ctx, object, schema_string);
             if (!Value::is_undefined(ctx, schema_value)) {
@@ -437,6 +447,11 @@ void RealmClass<T>::constructor(ContextType ctx, ObjectType this_object, size_t
             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, "migration");
+
+                if (config.schema_mode == SchemaMode::ResetFile) {
+                    throw std::invalid_argument("Cannot include 'migration' when 'deleteRealmIfMigrationNeeded' is set.");
+                }
+
                 config.migration_function = [=](SharedRealm old_realm, SharedRealm realm, realm::Schema&) {
                     auto old_realm_ptr = new SharedRealm(old_realm);
                     auto realm_ptr = new SharedRealm(realm);

tests/js/realm-tests.js

@@ -1025,5 +1025,137 @@ module.exports = {
         const realm2 = new Realm(config);
         TestCase.assertEqual(realm2.objects('TestObject').length, 0);
         realm.close();
-    }
+    },
+
+    testRealmDeleteRealmIfMigrationNeededVersionChanged: function() {
+        const schema = [{
+            name: 'TestObject',
+            properties: {
+                prop0: 'string',
+                prop1: 'int',
+            }
+        }];
+
+        var realm = new Realm({schema: schema});
+
+        realm.write(function() {
+            realm.create('TestObject', ['stringValue', 1]);
+        });
+
+        realm.close();
+
+
+        realm = new Realm({schema: schema, deleteRealmIfMigrationNeeded: true, schemaVersion: 1, migration: undefined });
+
+        // object should be gone as Realm should get deleted
+        TestCase.assertEqual(realm.objects('TestObject').length, 0);
+
+        // create a new object
+        realm.write(function() {
+            realm.create('TestObject', ['stringValue', 1]);
+        });
+
+        realm.close();
+
+        var migrationWasCalled = false;
+        realm = new Realm({schema: schema, deleteRealmIfMigrationNeeded: false, schemaVersion: 2, migration: function(oldRealm, newRealm) {
+            migrationWasCalled = true;
+        }});
+
+        // migration function should get called as deleteRealmIfMigrationNeeded is false
+        TestCase.assertEqual(migrationWasCalled, true);
+
+        // object should be there because Realm shouldn't get deleted
+        TestCase.assertEqual(realm.objects('TestObject').length, 1);
+        realm.close();
+    },
+
+    testRealmDeleteRealmIfMigrationNeededSchemaChanged: function() {
+        const schema = [{
+            name: 'TestObject',
+            properties: {
+                prop0: 'string',
+                prop1: 'int',
+            }
+        }];
+
+        const schema1 = [{
+            name: 'TestObject',
+            properties: {
+                prop0: 'string',
+                prop1: 'int',
+                prop2: 'float',
+            }
+        }];
+
+        const schema2 = [{
+            name: 'TestObject',
+            properties: {
+                prop0: 'string',
+                prop1: 'int',
+                prop2: 'float',
+                prop3: 'double'
+            }
+        }];
+
+        var realm = new Realm({schema: schema});
+
+        realm.write(function() {
+            realm.create('TestObject', {prop0: 'stringValue', prop1: 1});
+        });
+
+        realm.close();
+
+
+        // change schema
+        realm = new Realm({schema: schema1, deleteRealmIfMigrationNeeded: true, migration: undefined});
+
+        // object should be gone as Realm should get deleted
+        TestCase.assertEqual(realm.objects('TestObject').length, 0);
+
+        // create a new object
+        realm.write(function() {
+            realm.create('TestObject', {prop0: 'stringValue', prop1: 1, prop2: 1.0});
+        });
+
+        realm.close();
+
+
+        TestCase.assertThrows(function(e) {
+            // updating schema without changing schemaVersion OR setting deleteRealmIfMigrationNeeded = true should raise an error
+            new Realm({schema: schema2, deleteRealmIfMigrationNeeded: false, migration: function(oldRealm, newRealm) {}});
+        });
+
+        var migrationWasCalled = false;
+
+        // change schema again, but increment schemaVersion
+        realm = new Realm({schema: schema2, deleteRealmIfMigrationNeeded: false, schemaVersion: 1, migration: function(oldRealm, newRealm) {
+            migrationWasCalled = true;
+        }});
+
+        // migration function should get called as deleteRealmIfMigrationNeeded is false
+        TestCase.assertEqual(migrationWasCalled, true);
+
+        // object should be there because Realm shouldn't get deleted
+        TestCase.assertEqual(realm.objects('TestObject').length, 1);
+        realm.close();
+    },
+
+    testRealmDeleteRealmIfMigrationNeededIncompatibleConfig: function() {
+        const schema = [{
+            name: 'TestObject',
+            properties: {
+                prop0: 'string',
+                prop1: 'int',
+            }
+        }];
+
+        TestCase.assertThrows(function() {
+            new Realm({schema: schema, deleteRealmIfMigrationNeeded: true, readOnly: true});
+        }, "Cannot set 'deleteRealmIfMigrationNeeded' when 'readOnly' is set.")
+
+        TestCase.assertThrows(function() {
+            new Realm({schema: schema, deleteRealmIfMigrationNeeded: true, migration: function(oldRealm, newRealm) {}});
+        }, "Cannot include 'migration' when 'deleteRealmIfMigrationNeeded' is set.")
+    },
 };