test: ensure consistent CSS ordering

website/_dogfooding/clientModuleCSS.css

@@ -0,0 +1,11 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/* Used to test CSS insertion order */
+.test-marker-site-client-module {
+  content: "site-client-module";
+}

website/_dogfooding/dogfooding.config.js

@@ -55,6 +55,18 @@ const dogfoodingPluginInstances = [
       routeBasePath: '/tests/pages',
     }),
   ],
+
+  /** @type {import('@docusaurus/types').Plugin} */
+  function clientModuleTestPlugin() {
+    return {
+      getClientModules() {
+        return [
+          require.resolve('./clientModuleExample.ts'),
+          require.resolve('./clientModuleCSS.css'),
+        ];
+      },
+    };
+  },
 ];
 
 exports.dogfoodingPluginInstances = dogfoodingPluginInstances;

website/docusaurus.config.js

@@ -118,7 +118,6 @@ const config = {
     'static',
     path.join(__dirname, '_dogfooding/_asset-tests'),
   ],
-  clientModules: [require.resolve('./_dogfooding/clientModuleExample.ts')],
   themes: ['live-codeblock'],
   plugins: [
     FeatureRequestsPlugin,

website/package.json

@@ -10,15 +10,16 @@
     "deploy": "docusaurus deploy",
     "clear": "docusaurus clear",
     "serve": "docusaurus serve",
+    "test:css-order": "node testCSSOrder.js",
     "write-translations": "docusaurus write-translations",
     "write-heading-ids": "docusaurus write-heading-ids",
     "start:baseUrl": "cross-env BASE_URL='/build/' yarn start",
     "build:baseUrl": "cross-env BASE_URL='/build/' yarn build",
     "start:blogOnly": "cross-env yarn start --config=docusaurus.config-blog-only.js",
     "build:blogOnly": "cross-env yarn build --config=docusaurus.config-blog-only.js",
     "build:fast": "cross-env BUILD_FAST=true yarn build --locale en",
-    "netlify:build:production": "yarn docusaurus write-translations && yarn netlify:crowdin:delay && yarn netlify:crowdin:uploadSources && yarn netlify:crowdin:downloadTranslations && yarn build",
-    "netlify:build:deployPreview": "yarn docusaurus write-translations --locale fr --messagePrefix '(fr) ' && yarn build",
+    "netlify:build:production": "yarn docusaurus write-translations && yarn netlify:crowdin:delay && yarn netlify:crowdin:uploadSources && yarn netlify:crowdin:downloadTranslations && yarn build && yarn test:css-order",
+    "netlify:build:deployPreview": "yarn docusaurus write-translations --locale fr --messagePrefix '(fr) ' && yarn build && yarn test:css-order",
     "netlify:crowdin:delay": "node delayCrowdin.js",
     "netlify:crowdin:wait": "node waitForCrowdin.js",
     "netlify:crowdin:downloadTranslations": "yarn netlify:crowdin:wait && yarn --cwd .. crowdin:download:website",

website/src/css/custom.css

@@ -171,3 +171,11 @@ div[class^='announcementBar_'] {
   width: 1px;
   white-space: nowrap;
 }
+
+/* Used to test CSS insertion order */
+.test-marker-site-custom-css-unique-rule {
+  content: "site-custom-css-unique-rule";
+}
+.test-marker-site-custom-css-shared-rule {
+  max-width: 100%;
+}

website/src/pages/styles.module.css

@@ -153,3 +153,8 @@
     display: none;
   }
 }
+
+/* Used to test CSS insertion order */
+.test-marker-site-index-page {
+  content: "site-index-page";
+}

website/src/theme/Layout/index.tsx

@@ -0,0 +1,17 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import React from 'react';
+import type {Props} from '@theme/Layout';
+import Layout from '@theme-original/Layout';
+
+// This component is only used to test for CSS insertion order
+import './styles.module.css';
+
+export default function LayoutWrapper(props: Props): JSX.Element {
+  return <Layout {...props} />;
+}

website/src/theme/Layout/styles.module.css

@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/* Used to test CSS insertion order */
+.test-marker-theme-layout {
+  content: "theme-layout";
+}
+

website/testCSSOrder.js

@@ -0,0 +1,110 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+const path = require('path');
+const fs = require('fs');
+
+/*
+This verifies CSS ordering on the Docusaurus site itself,
+
+There are multiple ways to provide some CSS to Docusaurus
+and Docusaurus should guarantee a consistent CSS ordering over time
+
+See also
+- https://github.com/facebook/docusaurus/issues/3678
+- https://github.com/facebook/docusaurus/pull/5987
+
+TODO we should probably add a real e2e test in core instead of using our own website?
+Current solution looks good-enough for now
+
+ */
+
+// TODO temporary, the current order is bad and we should change/fix that
+const EXPECTED_CSS_MARKERS = [
+  // Note, Infima and site classes are optimized/deduplicated and put at the top
+  // We don't agree yet on what should be the order for those classes
+  // See https://github.com/facebook/docusaurus/pull/6222
+  '.markdown>h2',
+  '.button--outline.button--active',
+  '.DocSearch-Hit-content-wrapper',
+  '.navbar__title',
+  '--ifm-color-scheme:light',
+  '.test-marker-site-custom-css-shared-rule',
+  '.col[class*=col--]',
+  '.padding-vert--xl',
+  '.footer__link-item',
+  '.pagination__item',
+  '.pills__item',
+  '.tabs__item',
+
+  // Test markers
+  '.test-marker-site-custom-css-unique-rule',
+  '.test-marker-site-client-module',
+  '.test-marker-theme-layout',
+  '.test-marker-site-index-page',
+
+  // lazy loaded lib
+  '.DocSearch-Modal',
+];
+
+const cssDirName = path.join(__dirname, 'build', 'assets', 'css');
+
+const cssFileNames = fs
+  .readdirSync(cssDirName)
+  .filter((file) => file.endsWith('.css'));
+
+if (cssFileNames.length !== 1) {
+  throw new Error('unexpected: more than 1 css file');
+}
+const cssFile = path.join(cssDirName, cssFileNames[0]);
+
+console.log('Inspecting CSS file for test CSS markers', cssFile);
+
+const cssFileContent = fs.readFileSync(cssFile, 'utf8');
+
+const cssMarkersWithPositions = EXPECTED_CSS_MARKERS.map((marker) => {
+  const position = cssFileContent.indexOf(marker);
+  return {marker, position};
+});
+
+const missingCSSMarkers = cssMarkersWithPositions
+  .filter((m) => m.position === -1)
+  .map((m) => m.marker);
+
+if (missingCSSMarkers.length > 0) {
+  throw new Error(
+    `Some expected CSS marker classes could not be found in file ${cssFile}: \n- ${missingCSSMarkers.join(
+      '\n- ',
+    )}`,
+  );
+}
+
+// https://github.com/you-dont-need/You-Dont-Need-Lodash-Underscore#_sortby-and-_orderby
+const sortBy = (key) => (a, b) =>
+  // eslint-disable-next-line no-nested-ternary
+  a[key] > b[key] ? 1 : b[key] > a[key] ? -1 : 0;
+
+const sortedCSSMarkers = cssMarkersWithPositions
+  .concat()
+  .sort(sortBy('position'))
+  .map(({marker}) => marker);
+
+if (JSON.stringify(sortedCSSMarkers) === JSON.stringify(EXPECTED_CSS_MARKERS)) {
+  console.log(`Test CSS markers were found in the expected order:
+- ${sortedCSSMarkers.join('\n- ')}`);
+} else {
+  throw new Error(`Test CSS markers were found in an incorrect order.
+
+Expected order:
+- ${EXPECTED_CSS_MARKERS.join('\n- ')};
+
+Actual order:
+- ${sortedCSSMarkers.join('\n- ')};
+
+CSS file: ${cssFile}
+  `);
+}