feat: pass optional context to migration functions

Author: lukashass

src/Migration.ts

@@ -1,5 +1,9 @@
+// A declaration of a context passed to each migration.
+// eslint-disable-next-line @typescript-eslint/no-empty-interface
+export interface MigrationContext {}
+
 export interface Migration {
   id: string;
-  up(): Promise<void> | void;
-  down(): Promise<void> | void;
+  up(context?: MigrationContext): Promise<void> | void;
+  down(context?: MigrationContext): Promise<void> | void;
 }

src/index.ts

@@ -1,5 +1,5 @@
-import { Migration } from './Migration';
+import { Migration, MigrationContext } from './Migration';
 import { MongoMigrationStore } from './MongoMigrationStore';
 import up from './up';
 
-export { Migration, MongoMigrationStore, up };
+export { Migration, MigrationContext, MongoMigrationStore, up };

src/up.ts

@@ -1,10 +1,12 @@
-import { Migration } from './Migration';
+import { Migration, MigrationContext } from './Migration';
 import { MigrationStore } from './MigrationStore';
 
 export default async ({
+  context,
   migrations,
   migrationStore,
 }: {
+  context?: MigrationContext;
   migrations: Migration[];
   migrationStore: MigrationStore;
 }): Promise<void> => {
@@ -15,7 +17,7 @@ export default async ({
   );
 
   for await (const migration of migrationsToApply) {
-    await migration.up();
+    await migration.up(context);
     await migrationStore.insertMigration(migration);
   }
 };

test/up.test.ts

@@ -2,6 +2,12 @@ import { MongoMigrationStore } from '~/MongoMigrationStore';
 import up from '~/up';
 import { migration1, migration2, migration3 } from '$/__helpers__/TestMigrations';
 
+declare module '~/Migration' {
+  interface MigrationContext {
+    test: string;
+  }
+}
+
 jest.mock('~/MongoMigrationStore');
 
 const MongoMigrationStoreMock = MongoMigrationStore as jest.MockedClass<typeof MongoMigrationStore>;
@@ -53,4 +59,25 @@ describe('up', () => {
     expect(migration2.up).not.toHaveBeenCalled();
     expect(migration3.up).toHaveBeenCalledTimes(1);
   });
+
+  it('should pass a given context to the migrations up() function', async () => {
+    expect.assertions(2);
+
+    // given
+    const migrations = [migration1];
+    MongoMigrationStoreMock.mockImplementationOnce(() => ({
+      init: jest.fn(),
+      getAppliedMigrations: jest.fn().mockReturnValueOnce([]),
+      insertMigration: jest.fn(),
+    }));
+    const migrationStore = new MongoMigrationStore();
+    const context = { test: '123' };
+
+    // when
+    await up({ migrations, migrationStore, context });
+
+    // then
+    expect(migration1.up).toHaveBeenCalledTimes(1);
+    expect(migration1.up).toHaveBeenCalledWith(context);
+  });
 });