Extend Webpack Configuration

With extensibility in mind, the Build Command accepts a --webpackConfig option containing a path to a function which takes a webpack config, context and returns the resulting webpack config

Here you have an example of a file containing such a function:

apps/my-theme/webpack.custom.js

const { merge } = require('webpack-merge');

module.exports = function (nxShopifyConfig, { options, configuration }) {
  const myConfig = {
    plugins: [new NewWebpackPlugin()],
  };

  return merge(nxShopifyConfig, myConfig);
};

Then you would need to configure the webpackConfig option with the "apps/my-theme/webpack.custom.js" value.