TypeORM Migration: File must contain a TypeScript / JavaScript code and export a DataSource instance

Question

When trying to autogenerate migrations I get the following error.

File must contain a TypeScript / JavaScript code and export a DataSource instance

This is the command that I am running:

typeorm migration:generate projects/core/migrations/user -d db_config.ts -o

And my db_config.ts file looks like this:

import { DataSource } from "typeorm";

const AppDataSource = new DataSource({
  type: "postgres",
  host: process.env.PGHOST,
  port: 5432,
  username: process.env.PGUSER,
  password: process.env.PGPASSWORD,
  database: process.env.PGDATABASE,
  entities: ["./projects/**/entities/*.ts"],
  migrations: ["./projects/**/migrations/**.js"],
  synchronize: true,
  logging: false,
}); 

export default AppDataSource

My current file structure looks like this:

• back_end -- projects --- index.ts --- db_config.ts

And my index.ts file looks like this:

import express from "express";
import { AppDataSource } from "./data-source";
import budget_app from "./projects/budget_app/routes";

export const app = express();
const port = 3000;

AppDataSource.initialize()
  .then(() => {
    console.log("Data Source has been initialized!");
  })
  .catch((err) => {
    console.error("Error during Data Source initialization", err);
  });

// export default AppDataSource;

app.get("/", (req, res) => {
  res.send("Hello World!!!!");
});

app.use("/budget_app", budget_app);

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

I am also running this in a docker container along with my postgres database. I have confirmed that the connection works because if I do synchronize=true it will create the table just fine. I just can't create the migration.

So I'm confused and don't know where to go from here to fix the issue. Thanks for your help in advance!

Answer 1

I had trouble with migrations in typeorm, and finally found a solution that will work consistently.

For me, build and then using js datasource didn't work, So I am providing my solution for those who still struggle with typeorm-migrations.

Here is my step by step solution:

1. Create your datasource config in a file like datasource.config.ts.

   import * as mysqlDriver from 'mysql2';
   import {DataSourceOptions} from 'typeorm';
   import dotenv from 'dotenv';
   
   dotenv.config();
   
   export function getConfig() {
       return {
           driver: mysqlDriver,
           type: 'mysql',
           host: process.env.MYSQL_HOST,
           port: parseInt(process.env.MYSQL_PORT, 10),
           username: process.env.MYSQL_USER,
           password: process.env.MYSQL_PASSWORD,
           database: process.env.MYSQL_DB,
           synchronize: false,
           migrations: [__dirname + '/../../typeorm-migrations/*.{ts,js}'],
           entities: [__dirname + '/../**/entity/*.{ts,js}'],
       } as DataSourceOptions;
   }
   

2. Create a file with a name like migration.config.ts.

   const datasource = new DataSource(getConfig()); // config is one that is defined in datasource.config.ts file
   datasource.initialize();
   export default datasource;
   

3. Now you can define your migration commands in the package.json file.

   "migration:up": "ts-node -r tsconfig-paths/register --project ./tsconfig.json ./node_modules/.bin/typeorm migration:run -d config/migration.config.ts",
   "migration:down": "ts-node -r tsconfig-paths/register --project ./tsconfig.json ./node_modules/.bin/typeorm migration:revert -d config/migration.config.ts"
   

With running yarn run migration:up you will be able to run your defined migrations in typeorm-migrations folder.

Answer 2

I was running into the same issues (typeorm 0.3.4). I was just using npx typeorm migration:show -d ./src/data-source.ts and getting the same error as above (File must contain a TypeScript / JavaScript code and export a DataSource instance), while generating the migration file itself worked somehow, but not running/showing the migrations themselves.
My datasource looks like this

export const AppDataSource = new DataSource({
  type: 'postgres',
  url: process.env.DATABASE_URL,
  logging: true,
  entities: ['dist/entities/*.js'],
  migrations: ['dist/migrations/*.js'],
});

because my tsc output lives in /dist. So based on the comments above I started using the datasource file that was generated from TypeScript and the error message changed:

npx typeorm migration:run -d ./dist/appDataSource.js
CannotExecuteNotConnectedError: Cannot execute operation on "default" connection because connection is not yet established.

So I looked into the database logs and realized it wanted to connect to postgres with the standard unix user, it wasn't honoring the connection strings in the datasource code. I had to supply all environment variables to the command as well and it worked: DATABASE_URL=postgresql://postgres:postgres@localhost:5432/tsgraphqlserver npx typeorm migration:run -d ./dist/appDataSource.js