WatchMissingNodeModulesPlugin.js

// This Webpack plugin ensures `npm install <library>` forces a project rebuild.
// We’re not sure why this isn't Webpack's default behavior.
// See https://github.com/facebookincubator/create-react-app/issues/186.

function WatchMissingNodeModulesPlugin(nodeModulesPath) {
  this.nodeModulesPath = nodeModulesPath;
}

WatchMissingNodeModulesPlugin.prototype.apply = function (compiler) {
  compiler.plugin('emit', (compilation, callback) => {
    var missingDeps = compilation.missingDependencies;
    var nodeModulesPath = this.nodeModulesPath;

    // If any missing files are expected to appear in node_modules...
    if (missingDeps.some(file => file.indexOf(nodeModulesPath) !== -1)) {
      // ...tell webpack to watch node_modules recursively until they appear.
      compilation.contextDependencies.push(nodeModulesPath);
    }

    callback();
  });
}

module.exports = WatchMissingNodeModulesPlugin;