Webpack - How do you require an optional dependency in bundle (saslprep)

Question

I am using webpack to bundle a number of back-end scripts into a single file during my deployment process.

When connecting to the MongoDB database there is an option

Answer 1

Thanks to Brendan for steering me in the right direction. Ultimately the answer was found here: http://www.matthiassommer.it/software-architecture/webpack-node-modules/

The key piece of information being:

Webpack’s compiler converts the require() call to its own webpack_require(). At runtime it looks into its internal module registry.

Following the steps outlined therein the resolution becomes:

const path = require('path');
const webpack = require('webpack');

module.exports = {
    entry: './src/api/index.ts',
    target: 'node',
    mode: 'production',
    module: {
        rules: [
            {
                test: /\.tsx?$/,
                loader: 'ts-loader',
                exclude: /node_modules/
            }
        ]
    },
    resolve: {
        extensions: ['.js', '.tsx', '.ts', '.json'],
    },
    output: {
        filename: 'api.js',
        path: path.resolve(__dirname, 'dist'),
    },
    plugins: [
        new webpack.IgnorePlugin(/fsevents/),
        new webpack.IgnorePlugin(/blessed/),
    ],
    externals: {
        "saslprep": "require('saslprep')"
    }
};

Please note that in my testing the quotes around "saslprep" do appear to berequired when importing externals.

Answer 2

webpack should be 'seeing' that require('saslprep') code and bundling saslprep. You can confirm this by looking at the file(s) created by webpack and searching for something distinctive from the library's source code. I would look at the MongoDB code that is checking for that dependency -- it may be that the way they're checking that it exists doesn't work with the way that webpack bundles and defines the dependency. (Most authors of node libraries are probably not thinking about how the code will operate when bundled -- webpack can be used for Node, but it rarely is.) If that's the case, you might be able to reverse-engineer what the code is checking for and put it in place via an alias, etc.

Answer 3

I you use the webpack-node-externals package, you can also do this:

const nodeExternals = require("webpack-node-externals")

...

const webpackConfig = {
  ...
  externals: [nodeExternals({
    allowlist: ['saslprep']
  })],
  ...
}