import webpack from 'webpack' import { RawSource } from 'webpack-sources' import { join, relative, dirname } from 'path' import {IS_BUNDLED_PAGE_REGEX} from 'next-server/constants' const SSR_MODULE_CACHE_FILENAME = 'ssr-module-cache.js' // By default webpack keeps initialized modules per-module. // This means that if you have 2 entrypoints loaded into the same app // they will *not* share the same instance // This creates many issues when developers / libraries rely on the singleton pattern // As this pattern assumes every module will have 1 instance // This plugin overrides webpack's code generation step to replace `installedModules` // The replacement is a require for a file that's also generated here that only exports an empty object // Because of Node.js's single instance modules this makes webpack share all initialized instances // Do note that this module is only geared towards the `node` compilation target. // For the client side compilation we use `runtimeChunk: 'single'` export default class NextJsSsrImportPlugin { constructor (options) { this.options = options } apply (compiler) { const {outputPath} = this.options compiler.hooks.emit.tapAsync('NextJsSSRModuleCache', (compilation, callback) => { compilation.assets[SSR_MODULE_CACHE_FILENAME] = new RawSource(` /* This cache is used by webpack for instantiated modules */ module.exports = {} `) callback() }) compiler.hooks.compilation.tap('NextJsSSRModuleCache', (compilation) => { compilation.mainTemplate.hooks.localVars.intercept({ register (tapInfo) { if (tapInfo.name === 'MainTemplate') { const originalFn = tapInfo.fn tapInfo.fn = (source, chunk) => { // If the chunk is not part of the pages directory we have to keep the original behavior, // otherwise webpack will error out when the file is used before the compilation finishes // this is the case with mini-css-extract-plugin if (!IS_BUNDLED_PAGE_REGEX.exec(chunk.name) && chunk.name !== 'error-debug.js') { return originalFn(source, chunk) } const pagePath = join(outputPath, dirname(chunk.name)) let relativePathToBaseDir = relative(pagePath, join(outputPath, SSR_MODULE_CACHE_FILENAME)) if (chunk.name === 'error-debug.js') { relativePathToBaseDir = `./${relativePathToBaseDir}` } // Make sure even in windows, the path looks like in unix // Node.js require system will convert it accordingly const relativePathToBaseDirNormalized = relativePathToBaseDir.replace(/\\/g, '/') return webpack.Template.asString([ source, '// The module cache', `var installedModules = require('${relativePathToBaseDirNormalized}');` ]) } } return tapInfo } }) }) } }