Why are typescript and various @types packages installed as dependencies instead of devDependencies?

[ledhed2222]

More of a question than help needed. I just made a brand new app with the typescript template. I see the following in package.json:

  "dependencies": {
    "@testing-library/jest-dom": "^4.2.4",
    "@testing-library/react": "^9.5.0",
    "@testing-library/user-event": "^7.2.1",
    "@types/jest": "^24.9.1",
    "@types/node": "^12.12.53",
    "@types/react": "^16.9.44",
    "@types/react-dom": "^16.9.8",
    "react": "^16.13.1",
    "react-dom": "^16.13.1",
    "react-scripts": "3.4.1",
    "typescript": "^3.7.5"
  },

with nothing in devDependencies. I would think that only react, and react-dom among this are needed to run the app after packaging by webpack. Why are these not devDependencies?

[iansu]

Nothing is actually needed to run the app after building it. React and ReactDOM, along with all other dependencies and your code are all included in the compiled bundle. Since the app has no runtime dependencies it doesn't matter if you list dependencies under dependencies or devDependencies.

The reason we chose to use dependencies is because certain platforms like Heroku will only install dependencies when they build your app (this used to be true, I'm not sure if it still is).

When people submit PRs to "fix" this we usually direct them to this comment: #6180 (comment).

[ledhed2222]

Cool. Just to understand, does this mean that webpack is going to determine at transpile time what the runtime dependencies are and include them in the bundle? Therefore, the distinction between "dependencies" and "devDependencies" doesn't matter either way? If that's true, does that actually hold true to webpack when used outside of create-react-app?

Thank you!