better support for webpack 5

README.md

@@ -297,7 +297,7 @@ module.exports = {
               // you can specify a publicPath here
               // by default it uses publicPath in webpackOptions.output
               publicPath: '../',
-              hmr: process.env.NODE_ENV === 'development',
+              hmr: process.env.NODE_ENV === 'development', // webpack 4 only
             },
           },
           'css-loader',
@@ -379,7 +379,7 @@ module.exports = {
           {
             loader: MiniCssExtractPlugin.loader,
             options: {
-              hmr: process.env.NODE_ENV === 'development',
+              hmr: process.env.NODE_ENV === 'development', // webpack 4 only
             },
           },
           'css-loader',
@@ -394,6 +394,8 @@ module.exports = {
 
 ### Hot Module Reloading (HMR)
 
+Note: HMR is automatically supported in webpack 5. No need to configure it. Skip the following:
+
 The `mini-css-extract-plugin` supports hot reloading of actual css files in development.
 Some options are provided to enable HMR of both standard stylesheets and locally scoped CSS or CSS modules.
 Below is an example configuration of mini-css for HMR use with CSS modules.
@@ -424,7 +426,7 @@ module.exports = {
           {
             loader: MiniCssExtractPlugin.loader,
             options: {
-              // only enable hot in development
+              // only enable hot in development (webpack 4 only)
               hmr: process.env.NODE_ENV === 'development',
               // if hmr does not work, this is a forceful method.
               reloadAll: true,

src/CssLoadingRuntimeModule.js

@@ -0,0 +1,192 @@
+import { RuntimeGlobals, RuntimeModule, Template, util } from 'webpack';
+
+import { MODULE_TYPE } from './utils';
+
+const {
+  comparators: { compareModulesByIdentifier },
+} = util;
+
+const getCssChunkObject = (mainChunk, compilation) => {
+  const obj = {};
+  const { chunkGraph } = compilation;
+
+  for (const chunk of mainChunk.getAllAsyncChunks()) {
+    const modules = chunkGraph.getOrderedChunkModulesIterable(
+      chunk,
+      compareModulesByIdentifier
+    );
+    for (const module of modules) {
+      if (module.type === MODULE_TYPE) {
+        obj[chunk.id] = 1;
+        break;
+      }
+    }
+  }
+
+  return obj;
+};
+
+module.exports = class CssLoadingRuntimeModule extends RuntimeModule {
+  constructor(runtimeRequirements) {
+    super('css loading', 10);
+    this.runtimeRequirements = runtimeRequirements;
+  }
+
+  generate() {
+    const { chunk, compilation, runtimeRequirements } = this;
+    const {
+      runtimeTemplate,
+      outputOptions: { crossOriginLoading },
+    } = compilation;
+    const chunkMap = getCssChunkObject(chunk, compilation);
+
+    const withLoading =
+      runtimeRequirements.has(RuntimeGlobals.ensureChunkHandlers) &&
+      Object.keys(chunkMap).length > 0;
+    const withHmr = runtimeRequirements.has(
+      RuntimeGlobals.hmrDownloadUpdateHandlers
+    );
+
+    if (!withLoading && !withHmr) return null;
+
+    return Template.asString([
+      `var createStylesheet = ${runtimeTemplate.basicFunction(
+        'fullhref, resolve, reject',
+        [
+          'var linkTag = document.createElement("link");',
+          'linkTag.rel = "stylesheet";',
+          'linkTag.type = "text/css";',
+          'linkTag.onload = resolve;',
+          'linkTag.onerror = function(event) {',
+          Template.indent([
+            'var request = event && event.target && event.target.src || fullhref;',
+            'var err = new Error("Loading CSS chunk " + chunkId + " failed.\\n(" + request + ")");',
+            'err.code = "CSS_CHUNK_LOAD_FAILED";',
+            'err.request = request;',
+            'linkTag.parentNode.removeChild(linkTag)',
+            'reject(err);',
+          ]),
+          '};',
+          'linkTag.href = fullhref;',
+          crossOriginLoading
+            ? Template.asString([
+                `if (linkTag.href.indexOf(window.location.origin + '/') !== 0) {`,
+                Template.indent(
+                  `linkTag.crossOrigin = ${JSON.stringify(crossOriginLoading)};`
+                ),
+                '}',
+              ])
+            : '',
+          'var head = document.getElementsByTagName("head")[0];',
+          'head.appendChild(linkTag);',
+          'return linkTag;',
+        ]
+      )};`,
+      `var findStylesheet = ${runtimeTemplate.basicFunction('href, fullhref', [
+        'var existingLinkTags = document.getElementsByTagName("link");',
+        'for(var i = 0; i < existingLinkTags.length; i++) {',
+        Template.indent([
+          'var tag = existingLinkTags[i];',
+          'var dataHref = tag.getAttribute("data-href") || tag.getAttribute("href");',
+          'if(tag.rel === "stylesheet" && (dataHref === href || dataHref === fullhref)) return tag;',
+        ]),
+        '}',
+        'var existingStyleTags = document.getElementsByTagName("style");',
+        'for(var i = 0; i < existingStyleTags.length; i++) {',
+        Template.indent([
+          'var tag = existingStyleTags[i];',
+          'var dataHref = tag.getAttribute("data-href");',
+          'if(dataHref === href || dataHref === fullhref) return tag;',
+        ]),
+        '}',
+      ])};`,
+      `var loadStylesheet = ${runtimeTemplate.basicFunction(
+        'chunkId',
+        `return new Promise(${runtimeTemplate.basicFunction('resolve, reject', [
+          `var href = ${RuntimeGlobals.require}.miniCssF(chunkId);`,
+          `var fullhref = ${RuntimeGlobals.publicPath} + href;`,
+          'if(findStylesheet(href, fullhref)) return resolve();',
+          'createStylesheet(fullhref, resolve, reject);',
+        ])});`
+      )}`,
+      withLoading
+        ? Template.asString([
+            '// object to store loaded CSS chunks',
+            'var installedCssChunks = {',
+            Template.indent(
+              chunk.ids.map((id) => `${JSON.stringify(id)}: 0`).join(',\n')
+            ),
+            '};',
+            '',
+            `${
+              RuntimeGlobals.ensureChunkHandlers
+            }.miniCss = ${runtimeTemplate.basicFunction('chunkId, promises', [
+              `var cssChunks = ${JSON.stringify(chunkMap)};`,
+              'if(installedCssChunks[chunkId]) promises.push(installedCssChunks[chunkId]);',
+              'else if(installedCssChunks[chunkId] !== 0 && cssChunks[chunkId]) {',
+              Template.indent([
+                `promises.push(installedCssChunks[chunkId] = loadStylesheet(chunkId).then(${runtimeTemplate.basicFunction(
+                  '',
+                  'installedCssChunks[chunkId] = 0;'
+                )}, ${runtimeTemplate.basicFunction('e', [
+                  'delete installedCssChunks[chunkId];',
+                  'throw e;',
+                ])}));`,
+              ]),
+              '}',
+            ])};`,
+          ])
+        : '// no chunk loading',
+      '',
+      withHmr
+        ? Template.asString([
+            'var oldTags = [];',
+            'var newTags = [];',
+            `var applyHandler = ${runtimeTemplate.basicFunction('options', [
+              `return { dispose: ${runtimeTemplate.basicFunction('', [
+                'for(var i = 0; i < oldTags.length; i++) {',
+                Template.indent([
+                  'var oldTag = oldTags[i];',
+                  'if(oldTag.parentNode) oldTag.parentNode.removeChild(oldTag);',
+                ]),
+                '}',
+                'oldTags.length = 0;',
+              ])}, apply: ${runtimeTemplate.basicFunction('', [
+                'for(var i = 0; i < newTags.length; i++) newTags[i].rel = "stylesheet";',
+                'newTags.length = 0;',
+              ])} };`,
+            ])}`,
+            `${
+              RuntimeGlobals.hmrDownloadUpdateHandlers
+            }.miniCss = ${runtimeTemplate.basicFunction(
+              'chunkIds, removedChunks, removedModules, promises, applyHandlers, updatedModulesList',
+              [
+                'applyHandlers.push(applyHandler);',
+                `chunkIds.forEach(${runtimeTemplate.basicFunction('chunkId', [
+                  `var href = ${RuntimeGlobals.require}.miniCssF(chunkId);`,
+                  `var fullhref = ${RuntimeGlobals.publicPath} + href;`,
+                  'const oldTag = findStylesheet(href, fullhref);',
+                  'if(!oldTag) return;',
+                  `promises.push(new Promise(${runtimeTemplate.basicFunction(
+                    'resolve, reject',
+                    [
+                      `var tag = createStylesheet(fullhref, ${runtimeTemplate.basicFunction(
+                        '',
+                        [
+                          'tag.as = "style";',
+                          'tag.rel = "preload";',
+                          'resolve();',
+                        ]
+                      )}, reject);`,
+                      'oldTags.push(oldTag);',
+                      'newTags.push(tag);',
+                    ]
+                  )}));`,
+                ])});`,
+              ]
+            )}`,
+          ])
+        : '// no hmr',
+    ]);
+  }
+};

src/CssModule.js

@@ -2,6 +2,12 @@ import webpack from 'webpack';
 
 import { MODULE_TYPE } from './utils';
 
+const TYPES = new Set([MODULE_TYPE]);
+const CODE_GENERATION_RESULT = {
+  sources: new Map(),
+  runtimeRequirements: new Set(),
+};
+
 class CssModule extends webpack.Module {
   constructor({
     context,
@@ -20,9 +26,11 @@ class CssModule extends webpack.Module {
     this.content = content;
     this.media = media;
     this.sourceMap = sourceMap;
+    this.buildInfo = {};
+    this.buildMeta = {};
   }
 
-  // no source() so webpack doesn't do add stuff to the bundle
+  // no source() so webpack 4 doesn't do add stuff to the bundle
 
   size() {
     return this.content.length;
@@ -38,6 +46,16 @@ class CssModule extends webpack.Module {
     }`;
   }
 
+  // eslint-disable-next-line class-methods-use-this
+  getSourceTypes() {
+    return TYPES;
+  }
+
+  // eslint-disable-next-line class-methods-use-this
+  codeGeneration() {
+    return CODE_GENERATION_RESULT;
+  }
+
   nameForCondition() {
     const resource = this._identifier.split('!').pop();
     const idx = resource.indexOf('?');
@@ -60,6 +78,11 @@ class CssModule extends webpack.Module {
     return true;
   }
 
+  // eslint-disable-next-line class-methods-use-this
+  needBuild(context, callback) {
+    callback(null, false);
+  }
+
   build(options, compilation, resolver, fileSystem, callback) {
     this.buildInfo = {};
     this.buildMeta = {};