Narcissistic, Perfectly Modest


    1.4.8 • Public • Published


    Tweak the create-inferno-app webpack config(s) without using 'eject' and without creating a fork of the inferno-scripts.

    All the benefits of create-inferno-app without the limitations of "no config". You can add plugins, loaders whatever you need.

    All you have to do is create your app using create-inferno-app and then rewire it.

    Rewire Your App

    Tweak the create-inferno-app webpack config(s) without using 'eject' and without creating a fork of the inferno-scripts.

    All the benefits of create-inferno-app without the limitations of "no config". You can add plugins, loaders whatever you need.

    All you have to do is create your app using create-inferno-app and then rewire it.

    ⚠️ Please Note:

    By doing this you're breaking the ["guarantees"] that CIA provides. That is to say you now "own" the configs. No support will be provided. Proceed with caution.

    How to rewire your create-inferno-app project

    1) Install inferno-app-rewired

    $ npm install inferno-app-rewired --save-dev

    2) Create a config-overrides.js file in the root directory

    /* config-overrides.js */
    module.exports = function override(config, env) {
      //do stuff with the webpack config...
      return config;
    +-- your-project
    |   +-- config-overrides.js
    |   +-- node_modules
    |   +-- package.json
    |   +-- public
    |   +--
    |   +-- src

    Note: You can use one of the default rewires

    3) 'Flip' the existing calls to inferno-scripts in npm scripts

      /* package.json */
      "scripts": {
    -   "start": "inferno-scripts start",
    +   "start": "inferno-app-rewired start",
    -   "build": "inferno-scripts build",
    +   "build": "inferno-app-rewired build",
    -   "test": "inferno-scripts test --env=jsdom",
    +   "test": "inferno-app-rewired test --env=jsdom"

    4) Start the Dev Server

    $ npm start

    5) Build your app

    $ npm run build


    1) injectBabelPlugin

    Adding a Babel plugin can be done via the injectBabelPlugin(pluginName, config) function. You can also use the "rewire" packages from this repo or listed below to do common config modifications.

    const rewireMobX = require('inferno-app-rewire-mobx');
    const {injectBabelPlugin} = require('inferno-app-rewired');
    /* config-overrides.js */
    module.exports = function override(config, env) {
      // add a plugin
      config = injectBabelPlugin('emotion/babel',config)
      // use the MobX rewire
      config = rewireMobX(config,env);
      return config;

    2) compose

    You can use this util to compose rewires.


    /* config-overrides.js */
    module.exports = function override(config, env) {
      config = rewireLess(config, env);
      config = rewireMobX(config, env);
      return config;

    After use compose:

    /* config-overrides.js */
    const { compose } = require('inferno-app-rewired');
    module.exports = compose(
    //  custom config 
    module.exports = function(config, env){
      const rewires = compose(
      // do custom config
      // ...
      return rewires(config, env);

    Some change with rewire, if you want to add some extra param for rewire

    1. Optional params:
      you can see inferno-app-rewire-less

    2. Required params:

    // rewireSome.js
    function createRewire(requiredParams){
      return function rewire(config, env){
        return config
    module.exports = createRewire;

    Extended Configuration Options

    By default, the override-config.js file exports a single function to use when customising the webpack configuration for compiling your inferno app in development or production mode. It is possible to instead export an object from this file that contains up to three fields, each of which is a function. This alternative form allows you to also customise the configuration used for Jest (in testing), and for the Webpack Dev Server itself.

    This example implementation is used to demonstrate using each of the object require functions. In the example, the functions:

    • use the inferno-app-rewire-less package to add less support to your project
    • have some tests run conditionally based on .env variables
    • set the https certificates to use for the Development Server, with the filenames specified in .env file variables.
    module.exports = {
      // The Webpack config to use when compiling your inferno app for development or production.
      webpack: function(config, env) {
        // ...add your webpack config customisation, rewires, etc...
        // Example: add less support to your app.
        const rewireLess = require('inferno-app-rewire-less');
        config = rewireLess(config, env);
        return config;
      // The Jest config to use when running your jest tests - note that the normal rewires do not
      // work here.
      jest: function(config) {
        // ...add your jest config customisation...
        // Example: enable/disable some tests based on environment variables in the .env file.
        if (!config.testPathIgnorePatterns) {
          config.testPathIgnorePatterns = [];
        if (!process.env.RUN_COMPONENT_TESTS) {
        return config;
      // The function to use to create a webpack dev server configuration when running the development
      // server with 'npm run start' or 'yarn start'.
      // Example: set the dev server to use a specific certificate in https.
      devServer: function(configFunction) {
        // Return the replacement function for create-inferno-app to use to generate the Webpack
        // Development Server config. "configFunction" is the function that would normally have
        // been used to generate the Webpack Development server config - you can use it to create
        // a starting configuration to then modify instead of having to create a config from scratch.
        return function(proxy, allowedHost) {
          // Create the default config by calling configFunction with the proxy/allowedHost parameters
          const config = configFunction(proxy, allowedHost);
          // Change the https certificate options to match your certificate, using the .env file to
          // set the file paths & passphrase.
          const fs = require('fs');
          config.https = {
            key: fs.readFileSync(process.env.REACT_HTTPS_KEY, 'utf8'),
            cert: fs.readFileSync(process.env.REACT_HTTPS_CERT, 'utf8'),
            ca: fs.readFileSync(process.env.REACT_HTTPS_CA, 'utf8'),
            passphrase: process.env.REACT_HTTPS_PASS
          // Return your customised Webpack Development Server config.
          return config;

    1) Webpack configuration - Development & Production

    The webpack field is used to provide the equivalent to the single-function exported from config-overrides.js. This is where all the usual rewires are used. It is not able to configure compilation in test mode because test mode does not get run through Webpack at all (it runs in Jest). It is also not able to be used to customise the Webpack Dev Server that is used to serve pages in development mode because create-inferno-app generates a separate Webpack configuration for use with the dev server using different functions and defaults.

    2) Jest configuration - Testing

    Webpack is not used for compiling your application in Test mode - Jest is used instead. This means that any rewires specified in your webpack config customisation function will not be applied to your project in test mode.

    React-app-rewired automatically allows you to customise your Jest configuration in a jest section of your package.json file, including allowing you to set configuration fields that create-inferno-app would usually block you from being able to set. It also automatically sets up Jest to compile the project with Babel prior to running tests. Jest's configuration options are documented separately at the Jest website.

    If you want to add plugins and/or presets to the Babel configuration that Jest will use, you need to define those plugins/presets in either a babel section inside the package.json file or inside a .babelrc file. React-app-rewired alters the Jest configuration to use these definition files for specifying Babel options when Jest is compiling your inferno app. The format to use in the Babel section of package.json or the .babelrc file is documented separately at the Babel website.

    The jest field in the module.exports object in config-overrides.js is used to specify a function that can be called to customise the Jest testing configuration in ways that are not possible in the jest section of the package.json file. For example, it will allow you to change some configuration options based on environment variables. This function is passed the default create-inferno-app Jest configuration as a parameter and is required to return the modified Jest configuration that you want to use. A lot of the time you'll be able to make the configuration changes needed simply by using a combination of the package.json file's jest section and a .babelrc file (or babel section in package.json) instead of needing to provide this jest function in config-overrides.js.

    3) Webpack Dev Server

    When running in development mode, create-inferno-app does not use the usual Webpack config for the Development Server (the one that serves the app pages). This means that you cannot use the normal webpack section of the config-overrides.js server to make changes to the Development Server settings as those changes won't be applied.

    Instead of this, create-inferno-app expects to be able to call a function to generate the webpack dev server when needed. This function is provided with parameters for the proxy and allowedHost settings to be used in the webpack dev server (create-inferno-app retrieves the values for those parameters from your package.json file).

    React-app-rewired provides the ability to override this function through use of the devServer field in the module.exports object in config-overrides.js. It provides the devServer function a single parameter containing the default create-inferno-app function that is normally used to generate the dev server config (it cannot provide a generated version of the configuration because inferno-scripts is calling the generation function directly). React-app-rewired needs to receive as a return value a replacement function for create-inferno-app to then use to generate the Development Server configuration (i.e. the return value should be a new function that takes the two parameters for proxy and allowedHost and itself returns a Webpack Development Server configuration). The original inferno-scripts function is passed into the config-overrides.js devServer function so that you are able to easily call this yourself to generate your initial devServer configuration based on what the defaults used by create-inferno-app are.

    React-app-rewired requires a custom inferno-scripts package to provide the following files:

    • config/env.js
    • config/
    • config/
    • config/webpackDevServer.config.js
    • scripts/build.js
    • scripts/start.js
    • scripts/test.js
    • scripts/utils/createJestConfig.js

    3) Specify config-overrides as a directory

    Inferno-app-rewired imports your config-overrides.js file without the '.js' extension. This means that you have the option of creating a directory called config-overrides at the root of your project and exporting your overrides from the default index.js file inside that directory.

    If you have several custom overrides using a directory allows you to be able to put each override in a separate file. An example template that demonstrates this can be found in Guria/rewired-ts-boilerplate at Github.

    4) Specify config-overrides location from command line

    If you need to change the location of your config-overrides.js you can pass a command line option --config-overrides to the inferno-app-rewired script.

    Why This Project Exists

    See: Create React App — But I don’t wanna Eject.




    npm i inferno-app-rewired

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    • steveesamson