[contenthash] for webpack module ids

Index.js

const createHash = require('webpack/lib/util/createHash');

const usedIds = new Set();
compilation.hooks.beforeModuleIds.tap('URLImportPlugin', (modules) => {
  for (const module of modules) {
    // if the module has an id, and its got a path to a real file
    if (module.id === null && module.resource) {
      const hash = createHash(this.opts.hashFunction || 'md4');

      // grab the resource path, without any loader queries
      let resourcePath = module.resource;
      if (resourcePath.indexOf('?') > -1) {
        resourcePath = resourcePath.split('?')[0];
      }

      try {
        // update the generated hash with the buffer content of the literal file
        hash.update(fs.readFileSync(resourcePath));
      } catch (ex) {
        // whine and complain
        console.error('failed on', module.context, module.resource);
        throw ex;
      }

      const hashId = hash.digest(this.opts.hashDigest);
      let len = this.opts.hashDigestLength;
      while (usedIds.has(hashId.substr(0, len))) {
        len++;
      }
      // digest and set a shorter version of the hash as the module.id
      // React is now require('b3wS6Q')
      module.id = hashId.substr(0, len);
      usedIds.add(module.id);
    }
    
    // if the module contains a magic export
    const moduleSource = module?.originalSource?.().source?.() || '';
    if (moduleSource?.indexOf('externalize') > -1 || false) {
      // attach a flag to the modules build meta
      module.buildMeta = mergeDeep(module.buildMeta, { isExternalized: true });


      try {
        // look at refactoring this to use buildMeta not mutate id
        // rename the externalized module to a nice name which was parsed off the magic export
        // Nav can now be required as require('Nav')
        module.id = moduleSource.match(/\/\*\s*externalize\s*:\s*(\S+)\s*\*\//)[1];
        externalModules[module.id] = {};
      } catch (error) {
        throw new Error('external-import', error.message);
      }
    }
  }
});