feat: expose enableReverseMode from migrator (#1346)

Co-authored-by: Shinigami <[email protected]>

src/types.ts

@@ -656,6 +656,12 @@ export interface MigrationBuilder {
    */
   noTransaction: () => void;
 
+  /**
+   * Run the reverse of the migration. Useful for creating a new migration that
+   * reverts a previous migration.
+   */
+  enableReverseMode(): this;
+
   /**
    * The `db` client instance.
    *

test/1739900132875_names_reversed.js

@@ -0,0 +1,6 @@
+import { up as originalUp } from './1414549381268_names_promise.js';
+
+export const up = (pgm) => {
+  pgm.enableReverseMode();
+  return originalUp(pgm);
+};

test/migration.spec.ts

@@ -11,10 +11,12 @@ import type { Logger, RunnerOption } from '../src/types';
 
 const callbackMigration = '1414549381268_names.js';
 const promiseMigration = '1414549381268_names_promise.js';
+const reverseMigration = '1739900132875_names_reversed.js';
 const migrationsTable = 'pgmigrations';
 
 const actionsCallback = await import(`./${callbackMigration}`);
 const actionsPromise = await import(`./${promiseMigration}`);
+const reversePromise = await import(`./${reverseMigration}`);
 
 describe('migration', () => {
   const dbMock = {} as DBConnection;
@@ -154,6 +156,26 @@ describe('migration', () => {
       expect(queryMock).toHaveBeenCalled();
     });
 
+    it('should perform the inferred reverse operation when reverseMode is enabled', async () => {
+      const migration = new Migration(
+        dbMock,
+        reverseMigration,
+        reversePromise,
+        options,
+        {},
+        logger
+      );
+
+      await migration.apply('up');
+
+      expect(queryMock).toHaveBeenCalledTimes(4);
+      expect(queryMock).toHaveBeenNthCalledWith(1, 'BEGIN;');
+      expect(queryMock).toHaveBeenNthCalledWith(
+        2,
+        expect.stringMatching('DROP TABLE')
+      );
+    });
+
     it('should not call db.query on --dry-run', async () => {
       const migration = new Migration(
         dbMock,