Error: Cannot find module 'webpack' when d

Question

Judging from other topics (none which helped me), this seems to be a reoccurring issue, I am trying to deploy my app to heroku. It works fine with heroku local web, I have deployed the app and git heroku push to the master but as soon as I run heroku open, nothing loads and I get the following error:

Application error An error occurred in the application and your page could not be served. If you are the application owner, check your logs for details.

I checked my logs and it says:

Error: Cannot find module 'webpack'

My Package JSON has the following dependencies:

  "dependencies": {
    "babel-runtime": "^6.20.0",
    "react": "^15.4.1",
    "react-dom": "^15.4.1",
    "react-timestamp": "^3.1.0",
    "superagent": "^3.3.2"
  },
  "devDependencies": {
    "babel-core": "^6.21.0",
    "babel-eslint": "^7.1.1",
    "babel-loader": "^6.2.10",
    "babel-plugin-react-transform": "^2.0.2",
    "babel-plugin-transform-runtime": "^6.15.0",
    "babel-preset-es2015": "^6.18.0",
    "babel-preset-react": "^6.16.0",
    "babel-preset-stage-0": "^6.16.0",
    "cross-env": "^3.1.3",
    "css-loader": "^0.26.1",
    "eslint": "^3.12.2",
    "eslint-config-airbnb": "^13.0.0",
    "eslint-formatter-pretty": "^1.1.0",
    "eslint-plugin-compat": "^0.1.1",
    "eslint-plugin-import": "^2.2.0",
    "eslint-plugin-jsx-a11y": "2.2.3",
    "eslint-plugin-promise": "^3.4.0",
    "eslint-plugin-react": "^6.8.0",
    "extract-text-webpack-plugin": "^1.0.1",
    "react-transform-hmr": "^1.0.4",
    "style-loader": "^0.13.1",
    "webpack": "^1.14.0",
    "webpack-dev-server": "^1.16.2"
  }

Scripts:

  "scripts": {
    "start": "node server.js",
    "build": "cross-env BABEL_ENV=production ./node_modules/.bin/webpack --config webpack.config.production.js",
    "lint": "eslint --cache --ignore-path .gitignore --format=node_modules/eslint-formatter-pretty . *.js",
    "test": "npm run lint"
  },

What do I have to do to get it running on heroku? Do you need to install webpack on the server?? How does this work

NEW UPDATE TO DEPENDENCIES

  "dependencies": {
    "babel-runtime": "^6.20.0",
    "extract-text-webpack-plugin": "^1.0.1",
    "react": "^15.4.1",
    "react-dom": "^15.4.1",
    "react-timestamp": "^3.1.0",
    "superagent": "^3.3.2",
    "webpack": "^1.14.0",
    "webpack-combine-loaders": "^2.0.3",
    "webpack-dev-server": "^1.16.2",

      "babel-core": "^6.21.0",
      "babel-eslint": "^7.1.1",
      "babel-loader": "^6.2.10",
      "babel-plugin-react-transform": "^2.0.2",
      "babel-plugin-transform-runtime": "^6.15.0",
      "babel-preset-es2015": "^6.18.0",
      "babel-preset-react": "^6.16.0",
      "babel-preset-stage-0": "^6.16.0"

  },
  "devDependencies": {
    "cross-env": "^3.1.3",
    "css-loader": "^0.26.1",
    "eslint": "^3.12.2",
    "eslint-config-airbnb": "^13.0.0",
    "eslint-formatter-pretty": "^1.1.0",
    "eslint-plugin-compat": "^0.1.1",
    "eslint-plugin-import": "^2.2.0",
    "eslint-plugin-jsx-a11y": "2.2.3",
    "eslint-plugin-promise": "^3.4.0",
    "eslint-plugin-react": "^6.8.0",
    "react-transform-hmr": "^1.0.4",
    "style-loader": "^0.13.1"

  }

ERROR

2017-01-24T13:19:09.342589+00:00 app[web.1]: webpack: bundle is now VALID.
2017-01-24T13:20:01.547772+00:00 heroku[web.1]: Error R10 (Boot timeout) -> Web process failed to bind to $PORT within 60 seconds of launch
2017-01-24T13:20:01.547772+00:00 heroku[web.1]: Stopping process with SIGKILL
2017-01-24T13:20:01.695160+00:00 heroku[web.1]: Process exited with status 137
2017-01-24T13:20:01.703185+00:00 heroku[web.1]: State changed from starting to crashed
2017-01-24T13:25:57.948086+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=whapp.herokuapp.com request_id=9206d33a-fd68-461d-a4d9-dd620ad9d1c8 fwd="94.119.64.6" dyno= connect= service= status=503 bytes=
2017-01-24T13:25:58.798446+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=wheather-app.herokuapp.com request_id=48131770-43d1-4702-b201-244ec94a8011 fwd="94.119.64.17" dyno= connect= service= status=503 bytes=
2017-01-24T13:27:07.565562+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=whapp.herokuapp.com request_id=d38c3a55-6b83-4afa-85dc-944cb4607482 fwd="94.119.64.7" dyno= connect= service= status=503 bytes=
2017-01-24T13:27:08.488193+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=wheather-app.herokuapp.com request_id=fe267ccf-e202-46e6-aa47-1dc0fd2b8c78 fwd="94.119.64.4" dyno= connect= service= status=503 bytes=

Answer 1

Move webpack (and any other tools you rely on for building your Heroku slug from "devDependencies" to "dependencies" in your package.json.

You should also be able to call it with just plain "webpack" instead of ./node_modules/.bin/webpack.

By default, "devDependencies" only get installed in node_modules on Dev platforms, whereas Heroku is defined as a production platform.