Webpack build issue with mobx and mobx-react - reactjs

Question

I have a project that uses React and Mobx with Mobx-react.
My project runs perfectly fine locally. However, when built using webpack -p, I get a blank screen with the following error in the console:
webpack:///./~/mobx-react/index.js?:3 Uncaught Error: Cannot find module "mobx"
at webpackMissingModule (webpack:///./~/mobx-react/index.js?:3)
at webpackUniversalModuleDefinition (webpack:///./~/mobx-react/index.js?:3)
at eval (webpack:///./~/mobx-react/index.js?:10)
at Object.<anonymous> (bundle.js:18)
at n (bundle.js:1)
at eval (webpack:///./src/components/Category.jsx?:35)
at Object.<anonymous> (bundle.js:27)
at n (bundle.js:1)
at eval (webpack:///./src/components/CategoryNavsDates.jsx?:15)
at Object.<anonymous> (bundle.js:14)
Here is my webpack config:
var path = require('path');
var webpack = require('webpack');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const autoprefixer = require('autoprefixer')
var CopyWebpackPlugin = require('copy-webpack-plugin');
var BUILD_DIR = path.resolve(__dirname, 'build/');
var SOURCE_DIR = path.resolve(__dirname, 'src/');
module.exports = {
devtool: 'eval',
entry: SOURCE_DIR + '/index.jsx',
output: {
path: BUILD_DIR,
filename: 'bundle.js'
},
module: {
rules: [
{
test: /\.(js|jsx)$/,
exclude: /node_modules/,
loader: 'babel-loader',
query: {
cacheDirectory: true,
plugins: ['transform-decorators-legacy'],
presets: ['es2015', 'stage-0', 'react']
}
},
{
test: /\.css$/,
use: [
'style-loader',
{ loader: 'css-loader', options: { modules: true, importLoaders: 1, localIdentName: "[name]__[local]___[hash:base64:3] "} },
{ loader: 'postcss-loader', options: {} },
]
},
],
},
resolve: {
extensions: ['.js', '.jsx'],
},
plugins: [
new webpack.LoaderOptionsPlugin({
options: {
postcss: function () {
return [
require('postcss-import'),
require('postcss-cssnext'),
];
},
}
}),
new CopyWebpackPlugin([{ from: 'index.html', to: '' },])
],
devServer: {
historyApiFallback: true
},
};
There is only one file using Mobx in my entire project, and that is the file the error refers to, Category.jsx.
Category.jsx sample:
import { observer } from 'mobx-react'
import { observable } from 'mobx'
...
#observer class Category extends React.Component {
#observable showingSmallMenu = false
...
}
As I say this all works perfectly fine locally.
What could be the problem here?

Answer 1

Does it make a difference if you import mobx before mobx-react?

Answer 2

In my case, that is caused by:
alias: {
mobx: __dirname + '/node_modules/mobx/lib/mobx.es6.js'
}
Remove mobx alias, then the problem is solved