webpack-chain/src/Resolve.js

const ChainedMap = require('./ChainedMap');
const ChainedSet = require('./ChainedSet');
const Plugin = require('./Plugin');

module.exports = class extends ChainedMap {
  constructor(parent) {
    super(parent);
    this.alias = new ChainedMap(this);
    this.aliasFields = new ChainedSet(this);
    this.descriptionFiles = new ChainedSet(this);
    this.extensions = new ChainedSet(this);
    this.mainFields = new ChainedSet(this);
    this.mainFiles = new ChainedSet(this);
    this.modules = new ChainedSet(this);
    this.plugins = new ChainedMap(this);
    this.extend([
      'cachePredicate',
      'cacheWithContext',
      'concord',
      'enforceExtension',
      'enforceModuleExtension',
      'symlinks',
      'unsafeCache',
    ]);
  }

  plugin(name) {
    return this.plugins.getOrCompute(
      name,
      () => new Plugin(this, name, 'resolve.plugin'),
    );
  }

  toConfig() {
    return this.clean(
      Object.assign(this.entries() || {}, {
        alias: this.alias.entries(),
        aliasFields: this.aliasFields.values(),
        descriptionFiles: this.descriptionFiles.values(),
        extensions: this.extensions.values(),
        mainFields: this.mainFields.values(),
        mainFiles: this.mainFiles.values(),
        modules: this.modules.values(),
        plugins: this.plugins.values().map(plugin => plugin.toConfig()),
      }),
    );
  }

  merge(obj, omit = []) {
    const omissions = [
      'alias',
      'aliasFields',
      'descriptionFiles',
      'extensions',
      'mainFields',
      'mainFiles',
      'modules',
    ];

    if (!omit.includes('plugin') && 'plugin' in obj) {
      Object.keys(obj.plugin).forEach(name =>
        this.plugin(name).merge(obj.plugin[name]),
      );
    }

    omissions.forEach(key => {
      if (!omit.includes(key) && key in obj) {
        this[key].merge(obj[key]);
      }
    });

    return super.merge(obj, [...omit, ...omissions, 'plugin']);
  }
};