refactor(core): replace useDocusaurusContext().isClient by useIsBrowser()

packages/docusaurus-module-type-aliases/src/index.d.ts

@@ -179,6 +179,10 @@ declare module '@docusaurus/useDocusaurusContext' {
   export default function useDocusaurusContext(): DocusaurusContext;
 }
 
+declare module '@docusaurus/useIsBrowser' {
+  export default function useIsBrowser(): boolean;
+}
+
 declare module '@docusaurus/useBaseUrl' {
   export type BaseUrlOptions = {
     forcePrependBaseUrl?: boolean;

packages/docusaurus-theme-bootstrap/src/theme/ThemedImage/index.tsx

@@ -8,22 +8,22 @@
 import React from 'react';
 import clsx from 'clsx';
 
-import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
+import useIsBrowser from '@docusaurus/useIsBrowser';
 import useThemeContext from '@theme/hooks/useThemeContext';
 import type {Props} from '@theme/ThemedImage';
 
 import styles from './styles.module.css';
 
 const ThemedImage = (props: Props): JSX.Element => {
-  const {isClient} = useDocusaurusContext();
+  const isBrowser = useIsBrowser();
   const {isDarkTheme} = useThemeContext();
   const {sources, className, alt = '', ...propsRest} = props;
 
   type SourceName = keyof Props['sources'];
 
   const clientThemes: SourceName[] = isDarkTheme ? ['dark'] : ['light'];
 
-  const renderedSourceNames: SourceName[] = isClient
+  const renderedSourceNames: SourceName[] = isBrowser
     ? clientThemes
     : // We need to render both images on the server to avoid flash
       // See https://github.com/facebook/docusaurus/pull/3730

packages/docusaurus-theme-classic/src/theme/DocPage/index.tsx

@@ -8,7 +8,6 @@
 import React, {ReactNode, useState, useCallback} from 'react';
 import {MDXProvider} from '@mdx-js/react';
 
-import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
 import renderRoutes from '@docusaurus/renderRoutes';
 import type {PropVersionMetadata} from '@docusaurus/plugin-content-docs-types';
 import Layout from '@theme/Layout';
@@ -37,7 +36,6 @@ function DocPageContent({
   versionMetadata,
   children,
 }: DocPageContentProps): JSX.Element {
-  const {isClient} = useDocusaurusContext();
   const {pluginId, version} = versionMetadata;
 
   const sidebarName = currentDocRoute.sidebar;
@@ -57,7 +55,6 @@ function DocPageContent({
 
   return (
     <Layout
-      key={`${isClient}`} // TODO seems suspicious
       wrapperClassName={ThemeClassNames.wrapper.docPages}
       pageClassName={ThemeClassNames.page.docPage}
       searchMetadatas={{

packages/docusaurus-theme-classic/src/theme/Logo/index.tsx

@@ -17,7 +17,6 @@ import {useThemeConfig} from '@docusaurus/theme-common';
 const Logo = (props: Props): JSX.Element => {
   const {
     siteConfig: {title},
-    isClient,
   } = useDocusaurusContext();
   const {
     navbar: {title: navbarTitle, logo = {src: ''}},
@@ -37,7 +36,6 @@ const Logo = (props: Props): JSX.Element => {
       {...(logo.target && {target: logo.target})}>
       {logo.src && (
         <ThemedImage
-          key={`${isClient}`} // TODO seems suspicious
           className={imageClassName}
           sources={sources}
           alt={logo.alt || navbarTitle || title}

packages/docusaurus-theme-classic/src/theme/ThemedImage/index.tsx

@@ -8,22 +8,22 @@
 import React from 'react';
 import clsx from 'clsx';
 
-import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
+import useIsBrowser from '@docusaurus/useIsBrowser';
 import useThemeContext from '@theme/hooks/useThemeContext';
 import type {Props} from '@theme/ThemedImage';
 
 import styles from './styles.module.css';
 
 const ThemedImage = (props: Props): JSX.Element => {
-  const {isClient} = useDocusaurusContext();
+  const isBrowser = useIsBrowser();
   const {isDarkTheme} = useThemeContext();
   const {sources, className, alt = '', ...propsRest} = props;
 
   type SourceName = keyof Props['sources'];
 
   const clientThemes: SourceName[] = isDarkTheme ? ['dark'] : ['light'];
 
-  const renderedSourceNames: SourceName[] = isClient
+  const renderedSourceNames: SourceName[] = isBrowser
     ? clientThemes
     : // We need to render both images on the server to avoid flash
       // See https://github.com/facebook/docusaurus/pull/3730

packages/docusaurus-theme-classic/src/theme/Toggle/index.tsx

@@ -8,7 +8,7 @@
 import React, {useState, useRef, memo, CSSProperties} from 'react';
 import type {Props} from '@theme/Toggle';
 import {useThemeConfig} from '@docusaurus/theme-common';
-import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
+import useIsBrowser from '@docusaurus/useIsBrowser';
 
 import clsx from 'clsx';
 import './styles.css';
@@ -85,11 +85,11 @@ export default function (props: Props): JSX.Element {
       switchConfig: {darkIcon, darkIconStyle, lightIcon, lightIconStyle},
     },
   } = useThemeConfig();
-  const {isClient} = useDocusaurusContext();
+  const isBrowser = useIsBrowser();
 
   return (
     <Toggle
-      disabled={!isClient}
+      disabled={!isBrowser}
       icons={{
         checked: <Dark icon={darkIcon} style={darkIconStyle} />,
         unchecked: <Light icon={lightIcon} style={lightIconStyle} />,

packages/docusaurus-theme-classic/src/theme/hooks/useWindowSize.ts

@@ -47,10 +47,6 @@ function useWindowSize(): WindowSize {
   });
 
   useEffect(() => {
-    if (!ExecutionEnvironment.canUseDOM) {
-      return undefined;
-    }
-
     function updateWindowSize() {
       setWindowSize(getWindowSize());
     }

packages/docusaurus-theme-common/src/components/Details/index.tsx

@@ -6,7 +6,7 @@
  */
 
 import React, {ComponentProps, ReactElement, useRef, useState} from 'react';
-import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
+import useIsBrowser from '@docusaurus/useIsBrowser';
 import clsx from 'clsx';
 import {useCollapsible, Collapsible} from '../Collapsible';
 import styles from './styles.module.css';
@@ -30,7 +30,7 @@ export type DetailsProps = {
 } & ComponentProps<'details'>;
 
 const Details = ({summary, children, ...props}: DetailsProps): JSX.Element => {
-  const {isClient} = useDocusaurusContext();
+  const isBrowser = useIsBrowser();
   const detailsRef = useRef<HTMLDetailsElement>(null);
 
   const {collapsed, setCollapsed} = useCollapsible({
@@ -48,7 +48,7 @@ const Details = ({summary, children, ...props}: DetailsProps): JSX.Element => {
       data-collapsed={collapsed}
       className={clsx(
         styles.details,
-        {[styles.isClient]: isClient},
+        {[styles.isBrowser]: isBrowser},
         props.className,
       )}
       onMouseDown={(e) => {

packages/docusaurus-theme-common/src/components/Details/styles.module.css

@@ -46,9 +46,9 @@ CSS variables, meant to be overriden by final theme
 }
 
 /* When JS disabled/failed to load: we use the open property for arrow animation: */
-.details[open]:not(.isClient) > summary:before,
+.details[open]:not(.isBrowser) > summary:before,
 /* When JS works: we use the data-attribute for arrow animation */
-.details[data-collapsed='false'].isClient > summary:before {
+.details[data-collapsed='false'].isBrowser > summary:before {
   transform: rotate(90deg);
 }
 

packages/docusaurus-theme-common/src/utils/announcementBarUtils.tsx

@@ -14,7 +14,7 @@ import React, {
   useContext,
   createContext,
 } from 'react';
-import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
+import useIsBrowser from '@docusaurus/useIsBrowser';
 import {createStorageSlot} from './storageUtils';
 import {useThemeConfig} from './useThemeConfig';
 
@@ -39,10 +39,10 @@ type AnnouncementBarAPI = {
 
 const useAnnouncementBarContextValue = (): AnnouncementBarAPI => {
   const {announcementBar} = useThemeConfig();
-  const {isClient} = useDocusaurusContext();
+  const isBrowser = useIsBrowser();
 
   const [isClosed, setClosed] = useState(() => {
-    return isClient
+    return isBrowser
       ? // On client navigation: init with localstorage value
         isDismissedInStorage()
       : // On server/hydration: always visible to prevent layout shifts (will be hidden with css if needed)

packages/docusaurus-theme-live-codeblock/src/theme/Playground/index.js

@@ -10,6 +10,7 @@ import {LiveProvider, LiveEditor, LiveError, LivePreview} from 'react-live';
 import clsx from 'clsx';
 import Translate from '@docusaurus/Translate';
 import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
+import useIsBrowser from '@docusaurus/useIsBrowser';
 import usePrismTheme from '@theme/hooks/usePrismTheme';
 import styles from './styles.module.css';
 
@@ -51,8 +52,8 @@ function EditorWithHeader() {
 }
 
 export default function Playground({children, transformCode, ...props}) {
+  const isBrowser = useIsBrowser();
   const {
-    isClient,
     siteConfig: {
       themeConfig: {
         liveCodeBlock: {playgroundPosition},
@@ -64,8 +65,8 @@ export default function Playground({children, transformCode, ...props}) {
   return (
     <div className={styles.playgroundContainer}>
       <LiveProvider
-        key={isClient}
-        code={isClient ? children.replace(/\n$/, '') : ''}
+        key={isBrowser}
+        code={isBrowser ? children.replace(/\n$/, '') : ''}
         transformCode={transformCode || ((code) => `${code};`)}
         theme={prismTheme}
         {...props}>

packages/docusaurus-types/src/index.d.ts

@@ -125,7 +125,10 @@ export interface DocusaurusContext {
   globalData: Record<string, unknown>;
   i18n: I18n;
   codeTranslations: Record<string, string>;
-  isClient: boolean;
+
+  // Don't put mutable values here, to avoid triggering re-renders
+  // We could reconsider that choice if context selectors are implemented
+  // isBrowser: boolean; // Not here on purpose!
 }
 
 export interface Preset {

packages/docusaurus/src/client/App.tsx

@@ -5,46 +5,30 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import React, {useEffect, useState} from 'react';
+import React from 'react';
 
 import routes from '@generated/routes';
-import siteConfig from '@generated/docusaurus.config';
-import globalData from '@generated/globalData';
-import i18n from '@generated/i18n';
-import codeTranslations from '@generated/codeTranslations';
-import siteMetadata from '@generated/site-metadata';
 import renderRoutes from './exports/renderRoutes';
-import DocusaurusContext from './exports/context';
+import {BrowserContextProvider} from './exports/browserContext';
+import {DocusaurusContextProvider} from './exports/docusaurusContext';
 import PendingNavigation from './PendingNavigation';
 import BaseUrlIssueBanner from './baseUrlIssueBanner/BaseUrlIssueBanner';
 import Root from '@theme/Root';
 
 import './client-lifecycles-dispatcher';
 
 function App(): JSX.Element {
-  const [isClient, setIsClient] = useState(false);
-
-  useEffect(() => {
-    setIsClient(true);
-  }, []);
-
   return (
-    <DocusaurusContext.Provider
-      value={{
-        siteConfig,
-        siteMetadata,
-        globalData,
-        i18n,
-        codeTranslations,
-        isClient,
-      }}>
-      <Root>
-        <BaseUrlIssueBanner />
-        <PendingNavigation routes={routes}>
-          {renderRoutes(routes)}
-        </PendingNavigation>
-      </Root>
-    </DocusaurusContext.Provider>
+    <DocusaurusContextProvider>
+      <BrowserContextProvider>
+        <Root>
+          <BaseUrlIssueBanner />
+          <PendingNavigation routes={routes}>
+            {renderRoutes(routes)}
+          </PendingNavigation>
+        </Root>
+      </BrowserContextProvider>
+    </DocusaurusContextProvider>
   );
 }
 

packages/docusaurus/src/client/exports/BrowserOnly.tsx

@@ -6,18 +6,20 @@
  */
 
 import React from 'react';
-import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
+import useIsBrowser from '@docusaurus/useIsBrowser';
 
+// Similar comp to the one described here:
+// https://www.joshwcomeau.com/react/the-perils-of-rehydration/#abstractions
 function BrowserOnly({
   children,
   fallback,
 }: {
   children?: () => JSX.Element;
   fallback?: JSX.Element;
 }): JSX.Element | null {
-  const {isClient} = useDocusaurusContext();
+  const isBrowser = useIsBrowser();
 
-  if (isClient && children != null) {
+  if (isBrowser && children != null) {
     return <>{children()}</>;
   }
 

packages/docusaurus/src/client/exports/browserContext.tsx

@@ -0,0 +1,32 @@
+/**
+ * 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, {ReactNode, useEffect, useState} from 'react';
+
+// Encapsulate the logic to avoid React hydration problems
+// See https://www.joshwcomeau.com/react/the-perils-of-rehydration/
+// On first client-side render, we need to render exactly as the server rendered
+// isBrowser is set to true only after a successful hydration
+
+// Note, isBrowser is not part of useDocusaurusContext() for perf reasons
+// Using useDocusaurusContext() (much more common need) should not trigger re-rendering after a successful hydration
+
+export const Context = React.createContext<boolean>(false);
+
+export function BrowserContextProvider({
+  children,
+}: {
+  children: ReactNode;
+}): JSX.Element {
+  const [isBrowser, setIsBrowser] = useState(false);
+
+  useEffect(() => {
+    setIsBrowser(true);
+  }, []);
+
+  return <Context.Provider value={isBrowser}>{children}</Context.Provider>;
+}

packages/docusaurus/src/client/exports/docusaurusContext.tsx

@@ -0,0 +1,35 @@
+/**
+ * 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, {ReactNode} from 'react';
+import {DocusaurusContext} from '@docusaurus/types';
+
+import siteConfig from '@generated/docusaurus.config';
+import globalData from '@generated/globalData';
+import i18n from '@generated/i18n';
+import codeTranslations from '@generated/codeTranslations';
+import siteMetadata from '@generated/site-metadata';
+
+// Static value on purpose: don't make it dynamic!
+// Using context is still useful for testability reasons.
+const contextValue: DocusaurusContext = {
+  siteConfig,
+  siteMetadata,
+  globalData,
+  i18n,
+  codeTranslations,
+};
+
+export const Context = React.createContext<DocusaurusContext>(contextValue);
+
+export function DocusaurusContextProvider({
+  children,
+}: {
+  children: ReactNode;
+}): JSX.Element {
+  return <Context.Provider value={contextValue}>{children}</Context.Provider>;
+}