Using 'express' inside Electron main thread, cannot find module - express

Question

I'm trying to use express library in main.js file. It works fine on my dev build, but when I package the app I get
Error: Cannot find module 'express'
I'm not quite sure how electron main thread works, is it packaged separately by some other build tool, and do I need to define(include) package manually? My app is packaged by webpack, and I have included libraries in package.json. Every sample I have found just includes express library and moves on, I can't find any additional steps for this.
package.json
{
"name": "basic-electron-react-boilerplate",
"version": "0.7.0",
"description": "Minimal and modern react+electron+webpack boilerplate",
"author": "Phillip Barbiero",
"homepage": "https://github.com/pbarbiero/basic-electron-react-boilerplate",
"repository": {
"type": "git",
"url": "https://github.com/pbarbiero/basic-electron-react-boilerplate.git"
},
"build": {
"appId": "your.id",
"mac": {
"category": "your.app.category.type"
}
},
"license": "MIT",
"main": "main.js",
"scripts": {
"prod": "webpack --config webpack.build.config.js && electron --noDevServer .",
"test": "node test.js",
"dev": "webpack-dev-server --hot --host 0.0.0.0 --config=./webpack.dev.config.js",
"build": "webpack --config webpack.build.config.js",
"package": "webpack --config webpack.build.config.js",
"postpackage": "electron-packager ./ --out=./builds",
"pack": "electron-builder --dir",
"dist": "electron-builder"
},
"devDependencies": {
"#babel/core": "^7.1.2",
"#babel/plugin-proposal-class-properties": "^7.1.0",
"#babel/plugin-proposal-export-default-from": "^7.0.0",
"#babel/plugin-proposal-object-rest-spread": "^7.0.0",
"#babel/preset-env": "^7.1.0",
"#babel/preset-es2017": "^7.0.0-beta.53",
"#babel/preset-react": "^7.0.0",
"babel-core": "^6.24.1",
"babel-loader": "^8.0.4",
"babel-plugin-lodash": "^3.3.4",
"babel-preset-es2015": "^6.24.1",
"babel-preset-es2016": "^6.24.1",
"babel-preset-react": "^6.24.1",
"babel-preset-stage-2": "^6.24.1",
"babili-webpack-plugin": "^0.1.2",
"body-parser": "^1.18.3",
"css-loader": "^0.28.1",
"electron": "^1.7.8",
"electron-builder": "^20.28.4",
"electron-packager": "^9.1.0",
"express": "^4.16.4",
"extract-text-webpack-plugin": "^3.0.1",
"file-loader": "^1.1.5",
"html-webpack-plugin": "^2.28.0",
"react": "^16.0.0",
"react-dom": "^16.0.0",
"request": "^2.88.0",
"style-loader": "^0.19.0",
"webpack": "^3.6.0",
"webpack-dev-server": "^2.4.5"
},
"dependencies": {
"electron-fetch": "^1.2.1",
"electron-require": "^0.3.0",
"express": "^4.16.4",
"faker": "^4.1.0",
"lodash": "^4.17.11",
"moment": "^2.22.2",
"rc-time-picker": "^3.4.0",
"react-async-script-loader": "^0.3.0",
"react-dropdown": "^1.6.2",
"react-places-autocomplete": "^7.2.0",
"request": "^2.88.0",
"resolve-url-loader": "^3.0.0",
"semantic-ui-css": "^2.4.1",
"semantic-ui-react": "^0.82.5",
"styled-components": "^4.0.2"
}
}

Answer 1

You can run Express server inside Electron. Here is a sample repo for running express inside Electron.
You can fork a child process to run express app as follows
app = require("electron").remote.app),
node = require("child_process").fork(
`${app.getAppPath()}/express-app/bin/www`,
[],
{
stdio: ["pipe", "pipe", "pipe", "ipc"]
});
The express app used here is a generated one using express-generator.
The problem with your approach is that you are maintaining a single package.json file for both Electron and Express. Checkout Electron-React-Boilerplate, here i have two separate npm installation locations one is for Electron alone and other is for React stuffs. Electron-packager and Electron-builder works using this pattern. This is the reason why your process on main thread throws
Error: Cannot find module 'express'