extract-and-wrap-webpack-plugin.js

const { basename } = require('path');

const { ConcatSource } = require('webpack-sources');
const ModuleFilenameHelpers = require('webpack/lib/ModuleFilenameHelpers');

/**
 * Loosely based on wrapper-webpack-plugin
 * https://www.npmjs.com/package/wrapper-webpack-plugin
 *
 * Chunk deletion based on webpack-remove-empty-js-chunks-plugin
 * https://www.npmjs.com/package/webpack-remove-empty-js-chunks-plugin
 */
class ExtractAndWrapPlugin {
    constructor(args) {
        if (typeof args !== 'object') {
            throw new TypeError('Argument "args" must be an object.');
        }

        this.test = args.test || '';
        this.header = args.header || '';
        this.footer = args.footer || '';
    }

    apply(compiler) {
        const { header, footer, test } = this;

        const wrapChunks = (compilation, chunks) => {
            const extractChunk = chunkFilenameTest => {
                const selectedChunks = chunks.filter(
                    ({ name }) =>
                        chunkFilenameTest &&
                        typeof name === 'string' &&
                        ModuleFilenameHelpers.matchObject(
                            { test: chunkFilenameTest },
                            basename(name),
                        ),
                );
                if (selectedChunks.length) {
                    const files = selectedChunks.reduce((r, c) => r.concat(c.files), []);
                    const source = compilation.assets[files[0]].source();

                    // stop this chunk from outputting files
                    files.forEach(f => {
                        // eslint-disable-next-line no-param-reassign
                        delete compilation.assets[f];
                    });

                    // eslint-disable-next-line no-underscore-dangle
                    return source;
                }
                return null;
            };

            const headerSource = extractChunk(header);
            const footerSource = extractChunk(footer);

            if (headerSource || footerSource) {
                chunks.forEach(chunk => {
                    chunk.files.forEach(fileName => {
                        if (ModuleFilenameHelpers.matchObject({ test }, fileName)) {
                            // eslint-disable-next-line no-param-reassign
                            compilation.assets[fileName] = new ConcatSource(
                                ...[
                                    headerSource,
                                    compilation.assets[fileName],
                                    footerSource,
                                ].filter(Boolean),
                            );
                        }
                    });
                });
            }
        };

        compiler.hooks.compilation.tap('ExtractAndWrapPlugin', compilation => {
            compilation.hooks.optimizeChunkAssets.tapAsync(
                'ExtractAndWrapPlugin',
                (chunks, done) => {
                    // eslint-disable-next-line no-use-before-define
                    wrapChunks(compilation, chunks);
                    done();
                },
            );
        });
    }
}

module.exports = ExtractAndWrapPlugin;