Unknown file extension ".ts" for a TypeScript file

When I try to start my app on Heroku I got the following stack trace. It is just a basic ts.app like you see with ts-node and nodemon.

I am really interested in what the answer is going to be.

2020-05-30T00:03:12.201106+00:00 heroku[web.1]: Starting process with command `npm start`
2020-05-30T00:03:14.405285+00:00 app[web.1]: 
2020-05-30T00:03:14.405303+00:00 app[web.1]: > discordtoornamentmanager@1.0.0 start /app
2020-05-30T00:03:14.405303+00:00 app[web.1]: > ts-node src/App.ts
2020-05-30T00:03:14.405304+00:00 app[web.1]: 
2020-05-30T00:03:14.833655+00:00 app[web.1]: (node:23) ExperimentalWarning: The ESM module loader is experimental.
2020-05-30T00:03:14.839311+00:00 app[web.1]: TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /app/src/App.ts
2020-05-30T00:03:14.839312+00:00 app[web.1]:     at Loader.defaultGetFormat [as _getFormat] (internal/modules/esm/get_format.js:65:15)
2020-05-30T00:03:14.839314+00:00 app[web.1]:     at Loader.getFormat (internal/modules/esm/loader.js:113:42)
2020-05-30T00:03:14.839315+00:00 app[web.1]:     at Loader.getModuleJob (internal/modules/esm/loader.js:244:31)
2020-05-30T00:03:14.839315+00:00 app[web.1]:     at processTicksAndRejections (internal/process/task_queues.js:97:5)
2020-05-30T00:03:14.839316+00:00 app[web.1]:     at Loader.import (internal/modules/esm/loader.js:178:17)
2020-05-30T00:03:14.847801+00:00 app[web.1]: npm ERR! code ELIFECYCLE
2020-05-30T00:03:14.847998+00:00 app[web.1]: npm ERR! errno 1
2020-05-30T00:03:14.848957+00:00 app[web.1]: npm ERR! discordtoornamentmanager@1.0.0 start: `ts-node src/App.ts`
2020-05-30T00:03:14.849050+00:00 app[web.1]: npm ERR! Exit status 1
2020-05-30T00:03:14.849172+00:00 app[web.1]: npm ERR! 
2020-05-30T00:03:14.849254+00:00 app[web.1]: npm ERR! Failed at the discordtoornamentmanager@1.0.0 start script.
2020-05-30T00:03:14.849337+00:00 app[web.1]: npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
2020-05-30T00:03:14.854859+00:00 app[web.1]: 
2020-05-30T00:03:14.854998+00:00 app[web.1]: npm ERR! A complete log of this run can be found in:
2020-05-30T00:03:14.855069+00:00 app[web.1]: npm ERR!     /app/.npm/_logs/2020-05-30T00_03_14_850Z-debug.log
2020-05-30T00:03:14.907689+00:00 heroku[web.1]: Process exited with status 1
2020-05-30T00:03:14.943718+00:00 heroku[web.1]: State changed from starting to crashed

This is my package.json:

{
   "name": "discordtoornamentmanager",
   "version": "1.0.0",
   "description": "",
   "main": "dist/app.js",
   "type": "module",
   "scripts": {
      "test": "echo \"Error: no test specified\" && exit 1",
      "dev": "nodemon -x ts-node src/App.ts",
      "start": "ts-node src/App.ts"
   },
   "keywords": [],
   "author": "",
   "license": "ISC",
   "dependencies": {
      "@types/node": "^14.0.5",
      "axios": "^0.19.2",
      "discord.js": "^12.2.0",
      "pg": "^8.2.1",
      "reflect-metadata": "^0.1.10",
      "typeorm": "0.2.25",
      "typescript": "^3.9.3",
      "nodemon": "^2.0.4",
      "ts-node": "8.10.1"

   }
}

And this is my tsconfig:

{
   "compilerOptions": {
      "lib": [
         "es6"
      ],
      "target": "es6",
      "module": "commonjs",
      "moduleResolution": "node",
      "outDir": "dist",
      "resolveJsonModule": true,
      "emitDecoratorMetadata": true,
      "esModuleInterop": true,
      "experimentalDecorators": true,
      "sourceMap": true
   },
   "include": ["src/**/*.ts"],
   "exclude": ["node_modules", "**/*.spec.ts"]
}

Remove "type": "module" from package.json

https://github.com/TypeStrong/ts-node/issues/935

https://github.com/TypeStrong/ts-node/issues/1007#issuecomment-1163471306

If you don't want to remove "type": "module" (for example if you're using import statements in your .ts which allows the inference of types from modules), then you can use the following option in tsconfig.json:

{
  "compilerOptions": {
    "esModuleInterop": true,
  }
}

And then you can start the server with the config using ts-node.

Install:

npm install -g ts-node

Run:

ts-node-esm my_server.ts