Mastering License Extraction: A Step-by-Step Guide on Automating Sub-Package License Extraction with license-webpack-plugin

Prerequisites: Setting up your Webpack project

Before we dive into the automation process, make sure you have the following setup:

webpack installed in your project (version 4 or higher)

npm install webpack --save-dev

license-webpack-plugin installed in your project

npm install license-webpack-plugin --save-dev

Step 1: Configure license-webpack-plugin

To start automating license extraction, you need to configure the license-webpack-plugin in your Webpack configuration file. Create a new file called webpack.config.js (if you don’t already have one) and add the following code:

const LicenseWebpackPlugin = require('license-webpack-plugin');

module.exports = {
  // ... other configurations ...
  plugins: [
    new LicenseWebpackPlugin({
      perChunk: true, // Extract licenses per chunk (optional)
      output: './licenses.json', // Output file for extracted licenses
    }),
  ],
};

In this example, we’re telling the plugin to extract licenses per chunk (optional) and output the results to a file called licenses.json.

Step 2: Define sub-packages and their dependencies

Next, you need to define the sub-packages and their dependencies in your project. Let’s say you have two sub-packages: sub-pkg-1 and sub-pkg-2, each with its own dependencies. Create a new file called sub-packages.js and add the following code:

module.exports = {
  subPkg1: {
    name: 'sub-pkg-1',
    dependencies: ['dependency-1', 'dependency-2'],
  },
  subPkg2: {
    name: 'sub-pkg-2',
    dependencies: ['dependency-3', 'dependency-4'],
  },
};

In this example, we’re defining two sub-packages with their respective dependencies.

Step 3: Automate license extraction for sub-packages

To automate license extraction for sub-packages, you’ll need to create a custom function that iterates over the sub-packages and their dependencies. Add the following code to your webpack.config.js file:

const fs = require('fs');
const subPackages = require('./sub-packages');

const extractLicenses = () => {
  const licenses = {};

  Object.keys(subPackages).forEach((subPkgName) => {
    const subPkg = subPackages[subPkgName];
    const dependencies = subPkg.dependencies;

    dependencies.forEach((dependency) => {
      const pkg = require(`${dependency}/package.json`);
      const license = pkg.license;

      if (!licenses[dependency]) {
        licenses[dependency] = license;
      }
    });

    fs.writeFileSync(`./${subPkgName}-licenses.json`, JSON.stringify(licenses, null, 2));
  });
};

extractLicenses();

In this code, we’re iterating over the sub-packages and their dependencies, extracting the licenses, and writing them to separate JSON files (e.g., sub-pkg-1-licenses.json).

Step 4: Integrate with license-webpack-plugin

Finally, you need to integrate the custom function with the license-webpack-plugin. Update your webpack.config.js file with the following code:

const LicenseWebpackPlugin = require('license-webpack-plugin');

module.exports = {
  // ... other configurations ...
  plugins: [
    new LicenseWebpackPlugin({
      perChunk: true, // Extract licenses per chunk (optional)
      output: './licenses.json', // Output file for extracted licenses
      extractLicenses, // Integrate with our custom function
    }),
  ],
};

By integrating the custom function, you’re telling the plugin to use your automation script to extract licenses for sub-packages.

Conclusion

Voilà! You’ve successfully automated license extraction for sub-packages using the license-webpack-plugin. By following these steps, you can ensure compliance, transparency, and efficiency in your Webpack project. Remember to customize the script to fit your specific needs and enjoy the benefits of automated license extraction.

Troubleshooting Tips

If you encounter any issues during the automation process, here are some troubleshooting tips:

1. Check your dependencies**: Ensure that you’ve installed the required dependencies, including license-webpack-plugin and webpack.
2. Verify your configuration**: Double-check your Webpack configuration file and ensure that you’ve correctly configured the license-webpack-plugin.
3. Debug your custom function**: If you’re experiencing issues with your custom function, add console logs or use a debugger to identify the problem.