Private NPM library raise error "Module parse failed"

Question

I'm trying to create my libary with React and to use it locally (with my company git repository).

I can test my app while developping with npm run start. My app is running.

But when I want to use it in an other project, I got this error :

ERROR in ./node_modules/mylib/src/views/calendar.jsx Module parse failed: Unexpected token (10:53) You may need an appropriate loader to handle this file type.

The line involved is :

const Calendar = ({ month = moment(), dayCellTitle = <DayCellTitle />, header = <CalendarHeader/>, children }) => {

The package is imported like that :

"mylib": "git+ssh://git@gitlab.mycompany.ch:mylib/mylib.git"

I try this, but I got worst :

Plugin/Preset files are not allowed to export objects, only functions. In /home/xxxxx/Documents/workspaces/react-calendar/node_modules/babel-preset-stage-0/lib/index.js

Here the files of my package :

webpack.config.js

const path = require('path');
const pkg = require('./package.json');
const libraryName= pkg.name;
module.exports = {
  output: {
    path: path.join(__dirname, './dist'),
    filename: 'react-calendar.js',
    library: libraryName,
    libraryTarget: 'umd',
    publicPath: '/dist/',
    umdNamedDefine: true
  },
  module: {
    rules: [
      { test: /\.(js|jsx)$/,
        exclude: /node_modules/,
        use: ['babel-loader']
      }
    ]
  },
  resolve: {
    alias: {
      'react': path.resolve(__dirname, './node_modules/react'),
      'react-dom': path.resolve(__dirname, './node_modules/react-dom'),
    }
  },
  externals: {
    // Don't bundle react or react-dom
    react: {
      commonjs: "react",
      commonjs2: "react",
      amd: "React",
      root: "React"
    },
    "react-dom": {
      commonjs: "react-dom",
      commonjs2: "react-dom",
      amd: "ReactDOM",
      root: "ReactDOM"
    }
  }
};

package.json

{
  "name": "react-calendar",
  "version": "0.0.1",
  "description": "React Calendar UI by",
  "main": "./dist/lib/index.js",
  "scripts": {
    "start": "./node_modules/.bin/parcel docs/index.html",
    "build": "./node_modules/.bin/webpack --mode=production",
    "build:docs": "./node_modules/.bin/parcel build docs/index.js -d ./dist/docs && cp docs/index.html dist/docs/index.html",
    "test": "jest",
    "tdd": "jest --watch"
  },
  "author": "Xero",
  "license": "MIT",
  "dependencies": {
    "lodash": "^4.17.11",
    "mobx": "^5.9.0",
    "mobx-react": "^5.4.3",
    "moment": "^2.24.0",
    "moment-range": "^4.0.1",
    "react": "^16.2.0",
    "react-dom": "^16.2.0",
    "semantic-ui-css": "^2.4.1",
    "semantic-ui-react": "^0.85.0",
    "settings": "^0.1.1"
  },
  "peerDependencies": {
    "lodash": "^4.17.11",
    "mobx": "^5.9.0",
    "mobx-react": "^5.4.3",
    "moment": "^2.24.0",
    "moment-range": "^4.0.1",
    "react": "^16.2.0",
    "react-dom": "^16.2.0",
    "semantic-ui-css": "^2.4.1",
    "semantic-ui-react": "^0.85.0",
    "settings": "^0.1.1"
  },
  "devDependencies": {
    "@babel/core": "^7.0.0-0",
    "@babel/plugin-proposal-class-properties": "^7.3.0",
    "@babel/plugin-proposal-decorators": "^7.3.0",
    "@babel/preset-env": "^7.3.1",
    "@babel/preset-react": "^7.0.0",
    "babel-loader": "^8.0.5",
    "babel-plugin-module-resolver": "^3.1.3",
    "babel-plugin-transform-class-properties": "^6.24.1",
    "babel-preset-env": "^1.7.0",
    "babel-preset-react": "^6.24.1",
    "enzyme": "^3.8.0",
    "enzyme-adapter-react-16": "^1.9.1",
    "jest": "^24.1.0",
    "parcel-bundler": "^1.6.2",
    "react-test-renderer": "^16.8.0",
    "webpack": "^4.1.1",
    "webpack-cli": "^2.0.12",
    "webpack-node-externals": "^1.6.0"
  },
  "jest": {
    "moduleNameMapper": {
      "\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$": "<rootDir>/spec/javascript/__mocks__/fileMock.js",
      "\\.(css|scss|less)$": "<rootDir>/spec/javascript/__mocks__/styleMock.js"
    },
    "roots": [
      "src",
      "tests"
    ],
    "moduleFileExtensions": [
      "js",
      "jsx"
    ],
    "moduleDirectories": [
      "node_modules",
      "src"
    ],
    "setupFiles": [
      "<rootDir>/tests/setup.js"
    ]
  }
}

.babelrc

{
  "presets": ["@babel/preset-env", "@babel/preset-react",],
  "plugins":  [
    ["@babel/plugin-proposal-decorators", { "legacy": true }],
    ["@babel/plugin-proposal-class-properties", { "loose": true }]
  ]
}

Side question :

Is there a way to know if the library will be imported without error BEFORE doing the importation in an other project

Edit

I have added yarn run build to my package.json, and launching it do not raise any errors :

Entrypoint main [big] = react-calendar.js
 [45] (webpack)/buildin/module.js 497 bytes {0} [built]
 [48] (webpack)/buildin/global.js 472 bytes {0} [built]
[244] ./node_modules/moment/locale sync ^\.\/.*$ 3 KiB {0} [optional] [built]
[368] ./src/index.js + 52 modules 182 KiB {0} [built]
      | ./src/index.js 65 bytes [built]
      | ./src/views/calendar.jsx 1.17 KiB [built]
      | ./src/views/day_cell_title.jsx 358 bytes [built]
      | ./src/views/calendar_header.jsx 1.15 KiB [built]
      | ./src/store/calendar_store.js 3.85 KiB [built]
      | ./src/views/calendar_grid.jsx 1.49 KiB [built]
      | ./src/views/calendar_navigation_button.jsx 928 bytes [built]
      | ./src/views/calendar_title.jsx 290 bytes [built]
      | ./src/generators/month_generator.js 556 bytes [built]
      | ./src/painters/day_cell_color.js 593 bytes [built]
      | ./src/views/day_cell_content.jsx 547 bytes [built]
      | ./src/settings.js 332 bytes [built]
      | ./src/painters/event_color.js 374 bytes [built]
      | ./src/painters/range_color.js 591 bytes [built]
      | ./src/views/empty_day_cell_content.jsx 340 bytes [built]
      |     + 38 hidden modules
    + 743 hidden modules

Answer 1

You're redistributing your sources that contain JSX syntax. Usually, before publishing, you'll need to transform these. If not, then your dependents will need to configure their babel-loader with React support and ensure that they're not excluding your package modules.

So your configuration looks alright, except for the exclusion match:

 module: {
  rules: [
    { test: /\.(js|jsx)$/,
      exclude: /node_modules/,
      use: ['babel-loader']
    }
  ]
 }

I would recommend that you use { include } and list out the paths that should explicitly match. To find the path at which your package sources are located, use path.dirname(require.resolve('@yours/package-name')).

Answer 2

The issue was 2 things :

1. Build forgotten and not commited

I was not building my project (with yarn run build), and most of all, I was not commiting the compiled file (dist/main.js)

2. The import was wrong

Given the point 1., my import were wrong.

I was doing :

import {Calendar} from "project-react-calendar/src/views/calendar";

instead of :

import {Calendar} from "project-react-calendar";

That can be available, with this index.js :

import { Calendar } from './views/calendar'

export {
    Calendar
}

Answer 3

Your npm run start script seems to use parcel, not webpack I guess webpack.config.js simply doesn't affect it? Maybe you should make sure that proper loader is indeed launched by parcel.

"start": "./node_modules/.bin/parcel docs/index.html", // <- invokes parcel bundler
"build": "./node_modules/.bin/webpack --mode=production",

Try npm run build and if it succeeds, that will be exactly the case.