From 8dadfe9a5b86635e6b4abc1323f4df30f5e3c237 Mon Sep 17 00:00:00 2001
From: Joakim Carlstein <joakim@aboviq.com>
Date: Thu, 16 Nov 2023 11:24:00 +0100
Subject: [PATCH] feat(cli): support NodeJS callback style migration functions

---
 .changeset/blue-steaks-hide.md       |  5 +++++
 README.md                            |  1 +
 packages/cli/src/plugin-loader-js.ts | 22 +++++++++++++++++++---
 3 files changed, 25 insertions(+), 3 deletions(-)
 create mode 100644 .changeset/blue-steaks-hide.md

diff --git a/.changeset/blue-steaks-hide.md b/.changeset/blue-steaks-hide.md
new file mode 100644
index 0000000..00e89e8
--- /dev/null
+++ b/.changeset/blue-steaks-hide.md
@@ -0,0 +1,5 @@
+---
+'@emigrate/cli': minor
+---
+
+Support migration functions using the old NodeJS callback style API, i.e. accepting a callback as a single parameter which in turns takes any error as its first parameter (any other parameters are ignored)
diff --git a/README.md b/README.md
index e6d277f..7a7c877 100644
--- a/README.md
+++ b/README.md
@@ -17,6 +17,7 @@ It's effectively a successor of [klei-migrate](https://www.npmjs.com/package/kle
   - Emigrate makes sure the migration history does not get stuck in a locked state if that's the case
 - Supports any file type for your migration files
   - You can easily write migrations in JavaScript, TypeScript or plain SQL (or any other language)
+  - JavaScript migration files written using CommonJS or ES modules (ESM) are supported out of the box
   - You can customize the template for your migration files to fit your needs (or use a plugin to do it for you)
 - Easy to debug
   - Emigrate will store any errors that occur during migration in the migration history so you can easily debug them
diff --git a/packages/cli/src/plugin-loader-js.ts b/packages/cli/src/plugin-loader-js.ts
index f8f5e62..45cff1c 100644
--- a/packages/cli/src/plugin-loader-js.ts
+++ b/packages/cli/src/plugin-loader-js.ts
@@ -1,5 +1,21 @@
+import { promisify } from 'node:util';
 import { type LoaderPlugin } from '@emigrate/plugin-tools/types';
 
+// eslint-disable-next-line @typescript-eslint/ban-types
+const promisifyIfNeeded = <T extends Function>(fn: T) => {
+  if (fn.length === 0) {
+    return fn;
+  }
+
+  if (fn.length === 1) {
+    return promisify(fn);
+  }
+
+  throw new Error(
+    `Unexpected arguments length of migration function, expected 0 or 1 argument but got: ${fn.length} arguments`,
+  );
+};
+
 const loaderJs: LoaderPlugin = {
   loadableExtensions: ['.js', '.cjs', '.mjs'],
   async loadMigration(migration) {
@@ -7,7 +23,7 @@ const loaderJs: LoaderPlugin = {
 
     if (typeof migrationModule === 'function') {
       return async () => {
-        await migrationModule();
+        await promisifyIfNeeded(migrationModule)();
       };
     }
 
@@ -19,7 +35,7 @@ const loaderJs: LoaderPlugin = {
     ) {
       const migrationFunction = migrationModule.default;
       return async () => {
-        await migrationFunction();
+        await promisifyIfNeeded(migrationFunction)();
       };
     }
 
@@ -31,7 +47,7 @@ const loaderJs: LoaderPlugin = {
     ) {
       const migrationFunction = migrationModule.up;
       return async () => {
-        await migrationFunction();
+        await promisifyIfNeeded(migrationFunction)();
       };
     }