feat: details/summary theme / MDX component (#5216)

* Details component

* polish arrow animation

* fix text selection bug

* fix some edge cases + polish

* example of overriding baseClassName

* Move Details component to theme-common

* make component work even when JS is disabled or failed to load

* update arrow transform

* Details component: better handling of no-JS fallback mode: avoid delaying arrow navigation when JS (see review)

* prefix css vars with --docusaurus

* improve css arrow styling

* slightly change details/summary design

* better md doc + include quotes and details in doc

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

@@ -0,0 +1,24 @@
+/**
+ * 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 clsx from 'clsx';
+import {Details as DetailsGeneric} from '@docusaurus/theme-common';
+import type {Props} from '@theme/Details';
+import styles from './styles.module.css';
+
+// Should we have a custom details/summary comp in Infima instead of reusing alert classes?
+const InfimaClasses = 'alert alert--info';
+
+export default function Details({...props}: Props): JSX.Element {
+  return (
+    <DetailsGeneric
+      {...props}
+      className={clsx(InfimaClasses, styles.details, props.className)}
+    />
+  );
+}

packages/docusaurus-theme-classic/src/theme/Details/styles.module.css

@@ -0,0 +1,13 @@
+/**
+ * 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.
+ */
+
+.details {
+  --docusaurus-details-decoration-color: var(--ifm-alert-border-color);
+  --docusaurus-details-transition: transform var(--ifm-transition-fast) ease;
+  margin: 0 0 var(--ifm-spacing-vertical);
+  border: 1px solid var(--ifm-alert-border-color);
+}

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

@@ -5,10 +5,11 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import React, {isValidElement} from 'react';
+import React, {ComponentProps, isValidElement, ReactElement} from 'react';
 import Link from '@docusaurus/Link';
 import CodeBlock, {Props} from '@theme/CodeBlock';
 import Heading from '@theme/Heading';
+import Details from '@theme/Details';
 import type {MDXComponentsObject} from '@theme/MDXComponents';
 
 const MDXComponents: MDXComponentsObject = {
@@ -44,6 +45,20 @@ const MDXComponents: MDXComponentsObject = {
       />
     );
   },
+  details: (props): JSX.Element => {
+    const items = React.Children.toArray(props.children);
+    // Split summary item from the rest to pass it as a separate prop to the Detais theme component
+    const summary: ReactElement<
+      ComponentProps<'summary'>
+    > = (items as any[]).find((item) => item?.props?.mdxType === 'summary');
+    const children = <>{items.filter((item) => item !== summary)}</>;
+
+    return (
+      <Details {...props} summary={summary}>
+        {children}
+      </Details>
+    );
+  },
   h1: Heading('h1'),
   h2: Heading('h2'),
   h3: Heading('h3'),

packages/docusaurus-theme-classic/src/types.d.ts

@@ -328,6 +328,7 @@ declare module '@theme/MDXComponents' {
     readonly code: typeof CodeBlock;
     readonly a: (props: ComponentProps<'a'>) => JSX.Element;
     readonly pre: typeof CodeBlock;
+    readonly details: (props: ComponentProps<'details'>) => JSX.Element;
     readonly h1: (props: ComponentProps<'h1'>) => JSX.Element;
     readonly h2: (props: ComponentProps<'h2'>) => JSX.Element;
     readonly h3: (props: ComponentProps<'h3'>) => JSX.Element;
@@ -529,6 +530,12 @@ declare module '@theme/ThemedImage' {
   export default ThemedImage;
 }
 
+declare module '@theme/Details' {
+  export type Props = import('@docusaurus/theme-common').Details;
+  const Props: (props: Props) => JSX.Element;
+  export default Props;
+}
+
 declare module '@theme/ThemeProvider' {
   import type {ReactNode} from 'react';
 

packages/docusaurus-theme-common/copyUntypedFiles.js

@@ -0,0 +1,20 @@
+/**
+ * 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-extra');
+
+/**
+ * Copy all untyped and static assets files to lib.
+ */
+const srcDir = path.resolve(__dirname, 'src');
+const libDir = path.resolve(__dirname, 'lib');
+fs.copySync(srcDir, libDir, {
+  filter(filepath) {
+    return !/__tests__/.test(filepath) && !/\.tsx?$/.test(filepath);
+  },
+});

packages/docusaurus-theme-common/package.json

@@ -5,8 +5,8 @@
   "main": "./lib/index.js",
   "types": "./lib/index.d.ts",
   "scripts": {
-    "build": "tsc",
-    "watch": "tsc --watch"
+    "build": "node copyUntypedFiles.js && tsc",
+    "watch": "node copyUntypedFiles.js && tsc --watch"
   },
   "publishConfig": {
     "access": "public"
@@ -23,6 +23,8 @@
     "@docusaurus/plugin-content-docs": "2.0.0-beta.3",
     "@docusaurus/plugin-content-pages": "2.0.0-beta.3",
     "@docusaurus/types": "2.0.0-beta.3",
+    "clsx": "^1.1.1",
+    "fs-extra": "^10.0.0",
     "tslib": "^2.1.0"
   },
   "devDependencies": {

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

@@ -164,7 +164,12 @@ type CollapsibleBaseProps = {
   collapsed: boolean;
   children: ReactNode;
   animation?: CollapsibleAnimationConfig;
+  onCollapseTransitionEnd?: (collapsed: boolean) => void;
   className?: string;
+
+  // This is mostly useful for details/summary component where ssrStyle is not needed (as details are hidden natively)
+  // and can mess-up with the default native behavior of the browser when JS fails to load or is disabled
+  disableSSRStyle?: boolean;
 };
 
 function CollapsibleBase({
@@ -172,7 +177,9 @@ function CollapsibleBase({
   collapsed,
   children,
   animation,
+  onCollapseTransitionEnd,
   className,
+  disableSSRStyle,
 }: CollapsibleBaseProps) {
   // any because TS is a pain for HTML element refs, see https://twitter.com/sebastienlorber/status/1412784677795110914
   const collapsibleRef = useRef<any>(null);
@@ -183,7 +190,7 @@ function CollapsibleBase({
     <As
       // @ts-expect-error: see https://twitter.com/sebastienlorber/status/1412784677795110914
       ref={collapsibleRef}
-      style={getSSRStyle(collapsed)}
+      style={disableSSRStyle ? undefined : getSSRStyle(collapsed)}
       onTransitionEnd={(e) => {
         if (e.propertyName !== 'height') {
           return;
@@ -197,10 +204,12 @@ function CollapsibleBase({
           parseInt(currentCollapsibleElementHeight, 10) === el.scrollHeight
         ) {
           applyCollapsedStyle(el, false);
+          onCollapseTransitionEnd?.(false);
         }
 
         if (currentCollapsibleElementHeight === CollapsedStyles.height) {
           applyCollapsedStyle(el, true);
+          onCollapseTransitionEnd?.(true);
         }
       }}
       className={className}>
@@ -239,7 +248,7 @@ type CollapsibleProps = CollapsibleBaseProps & {
   lazy: boolean;
 };
 
-export function Collapsible({lazy, ...props}: CollapsibleProps) {
+export function Collapsible({lazy, ...props}: CollapsibleProps): JSX.Element {
   const Comp = lazy ? CollapsibleLazy : CollapsibleBase;
   return <Comp {...props} />;
 }

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

@@ -0,0 +1,94 @@
+/**
+ * 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, {ComponentProps, ReactElement, useRef, useState} from 'react';
+import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
+import clsx from 'clsx';
+import {useCollapsible, Collapsible} from '../Collapsible';
+import styles from './styles.module.css';
+
+function isInSummary(node: HTMLElement | null): boolean {
+  if (!node) {
+    return false;
+  }
+  return node.tagName === 'SUMMARY' || isInSummary(node.parentElement);
+}
+
+function hasParent(node: HTMLElement | null, parent: HTMLElement): boolean {
+  if (!node) {
+    return false;
+  }
+  return node === parent || hasParent(node.parentElement, parent);
+}
+
+export type DetailsProps = {
+  summary?: ReactElement;
+} & ComponentProps<'details'>;
+
+const Details = ({summary, children, ...props}: DetailsProps): JSX.Element => {
+  const {isClient} = useDocusaurusContext();
+  const detailsRef = useRef<HTMLDetailsElement>(null);
+
+  const {collapsed, setCollapsed} = useCollapsible({
+    initialState: !props.open,
+  });
+  // We use a separate prop because it must be set only after animation completes
+  // Otherwise close anim won't work
+  const [open, setOpen] = useState(props.open);
+
+  return (
+    <details
+      {...props}
+      ref={detailsRef}
+      open={open}
+      data-collapsed={collapsed}
+      className={clsx(
+        styles.details,
+        {[styles.isClient]: isClient},
+        props.className,
+      )}
+      onMouseDown={(e) => {
+        const target = e.target as HTMLElement;
+        // Prevent a double-click to highlight summary text
+        if (isInSummary(target) && e.detail > 1) {
+          e.preventDefault();
+        }
+      }}
+      onClick={(e) => {
+        e.stopPropagation(); // For isolation of multiple nested details/summary
+        const target = e.target as HTMLElement;
+        const shouldToggle =
+          isInSummary(target) && hasParent(target, detailsRef.current!);
+        if (!shouldToggle) {
+          return;
+        }
+        e.preventDefault();
+        if (collapsed) {
+          setCollapsed(false);
+          setOpen(true);
+        } else {
+          setCollapsed(true);
+          // setOpen(false); // Don't do this, it breaks close animation!
+        }
+      }}>
+      {summary}
+
+      <Collapsible
+        lazy={false} // Content might matter for SEO in this case
+        collapsed={collapsed}
+        disableSSRStyle // Allows component to work fine even with JS disabled!
+        onCollapseTransitionEnd={(newCollapsed) => {
+          setCollapsed(newCollapsed);
+          setOpen(!newCollapsed);
+        }}>
+        <div className={styles.collapsibleContent}>{children}</div>
+      </Collapsible>
+    </details>
+  );
+};
+
+export default Details;

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

@@ -0,0 +1,59 @@
+/**
+ * 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.
+ */
+
+/*
+CSS variables, meant to be overriden by final theme
+ */
+.details {
+  --docusaurus-details-summary-arrow-size: 0.38rem;
+  --docusaurus-details-transition: transform 200ms ease;
+  --docusaurus-details-decoration-color: grey;
+}
+
+.details > summary {
+  position: relative;
+  cursor: pointer;
+  list-style: none;
+  margin-left: 1.8rem;
+}
+
+.details > summary::-webkit-details-marker {
+  display: none;
+}
+
+.details > summary:before {
+  position: absolute;
+  top: 0.45rem;
+  left: -1.2rem;
+
+  /* CSS-only Arrow */
+  content: '';
+  width: 0;
+  height: 0;
+  border-top: var(--docusaurus-details-summary-arrow-size) solid transparent;
+  border-bottom: var(--docusaurus-details-summary-arrow-size) solid transparent;
+  border-left: var(--docusaurus-details-summary-arrow-size) solid
+    var(--docusaurus-details-decoration-color);
+
+  /* Arrow rotation anim */
+  transform: rotate(0deg);
+  transition: var(--docusaurus-details-transition);
+  transform-origin: calc(var(--docusaurus-details-summary-arrow-size) / 2) 50%;
+}
+
+/* When JS disabled/failed to load: we use the open property for arrow animation: */
+.details[open]:not(.isClient) > summary:before,
+/* When JS works: we use the data-attribute for arrow animation */
+.details[data-collapsed='false'].isClient > summary:before {
+  transform: rotate(90deg);
+}
+
+.collapsibleContent {
+  margin-top: 1rem;
+  border-top: 1px solid var(--docusaurus-details-decoration-color);
+  padding-top: 1rem;
+}

packages/docusaurus-theme-common/src/index.ts

@@ -37,11 +37,14 @@ export {useLocationChange} from './utils/useLocationChange';
 
 export {usePrevious} from './utils/usePrevious';
 
-export {useCollapsible, Collapsible} from './utils/useCollapsible';
+export {useCollapsible, Collapsible} from './components/Collapsible';
 export type {
   UseCollapsibleConfig,
   UseCollapsibleReturns,
-} from './utils/useCollapsible';
+} from './components/Collapsible';
+
+export {default as Details} from './components/Details';
+export type {DetailsProps} from './components/Details';
 
 export {
   MobileSecondaryMenuProvider,

website/docs/guides/markdown-features/_markdown-partial-example.mdx

@@ -0,0 +1,3 @@
+<span>Hello {props.name}</span>
+
+This is text some content from `_markdown-partial-example.md`.

website/docs/guides/markdown-features/markdown-features-intro.mdx

@@ -1,23 +1,115 @@
 ---
 id: introduction
-title: Markdown Features introduction
+title: Markdown Features
 sidebar_label: Introduction
 description: Docusaurus uses GitHub Flavored Markdown (GFM). Find out more about Docusaurus-specific features when writing Markdown.
 slug: /markdown-features
 ---
 
+```mdx-code-block
+import BrowserWindow from '@site/src/components/BrowserWindow';
+```
+
 Documentation is one of your product's interfaces with your users. A well-written and well-organized set of docs helps your users understand your product quickly. Our aligned goal here is to help your users find and understand the information they need, as quickly as possible.
 
 Docusaurus 2 uses modern tooling to help you compose your interactive documentations with ease. You may embed React components, or build live coding blocks where your users may play with the code on the spot. Start sharing your eureka moments with the code your audience cannot walk away from. It is perhaps the most effective way of attracting potential users.
 
 In this section, we'd like to introduce you to the tools we've picked that we believe will help you build a powerful documentation. Let us walk you through with an example.
 
-Markdown is a syntax that enables you to write formatted content in a readable syntax.
-
-The [standard Markdown syntax](https://daringfireball.net/projects/markdown/syntax) is supported, and we use [MDX](https://mdxjs.com/) as the parsing engine, which can do much more than just parsing Markdown, like rendering React components inside your documents.
-
 :::important
 
 This section assumes you are using the official Docusaurus content plugins.
 
 :::
+
+## Standard features
+
+Markdown is a syntax that enables you to write formatted content in a readable syntax.
+
+The [standard Markdown syntax](https://daringfireball.net/projects/markdown/syntax) is supported, and we use [MDX](https://mdxjs.com/) as the parsing engine, which can do much more than just parsing Markdown, like rendering React components inside your documents.
+
+```md
+### My Doc Section
+
+Hello world message with some **bold** text, some _italic_ text and a [link](/)
+
+![img alt](/img/docusaurus.png)
+```
+
+```mdx-code-block
+<BrowserWindow>
+
+<h2>My Doc Section</h2>
+
+Hello world message with some **bold** text, some _italic_ text and a [link](/)
+
+![img alt](/img/docusaurus.png)
+
+</BrowserWindow>
+```
+
+## Quotes
+
+Markdown quotes are beautifully styled:
+
+```md
+> This is a quote
+```
+
+> This is a quote
+
+## Details
+
+Markdown can embed HTML elements, and [`details`](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/details) HTML elements are beautifully styled:
+
+```md
+### Details element example
+
+<details>
+  <summary>Toggle me!</summary>
+  <div>
+    <div>This is the detailed content</div>
+    <details>
+      <summary>
+        <div>Nested toggle!</div>
+        <div>Some surprise inside...</div>
+      </summary>
+      <div>
+        😲😲😲😲😲
+      </div>
+    </details>
+  </div>
+</details>
+```
+
+```mdx-code-block
+<BrowserWindow>
+
+<h3>Details element example</h3>
+
+<details>
+  <summary>Toggle me!</summary>
+  <div>
+    <div>This is the detailed content</div>
+    <details>
+      <summary>
+        <div>Nested toggle!</div>
+        <div>Some surprise inside...</div>
+      </summary>
+      <div>
+        😲😲😲😲😲
+      </div>
+    </details>
+  </div>
+</details>
+
+</BrowserWindow>
+
+<br/>
+```
+
+:::note
+
+In practice, those are not really HTML elements, but React JSX elements, which we'll cover next!
+
+:::

website/docs/guides/markdown-features/markdown-features-react.mdx

@@ -1,11 +1,13 @@
 ---
 id: react
-title: Using React
+title: MDX and React
 description: Using the power of React in Docusaurus Markdown documents, thanks to MDX
 slug: /markdown-features/react
 ---
 
+```mdx-code-block
 import BrowserWindow from '@site/src/components/BrowserWindow';
+```
 
 ## Using JSX in Markdown {#using-jsx-in-markdown}
 
@@ -17,6 +19,14 @@ While both `.md` and `.mdx` files are parsed using MDX, some of the syntax are t
 
 :::
 
+:::caution
+
+MDX is not [100% compatible with CommonMark](https://github.com/facebook/docusaurus/issues/3018).
+
+Use the **[MDX playground](https://mdxjs.com/playground)** to ensure that your syntax is valid MDX.
+
+:::
+
 Try this block here:
 
 ```jsx
@@ -126,21 +136,27 @@ This feature is experimental and might be subject to API breaking changes in the
 
 ## Importing Markdown {#importing-markdown}
 
-You can use Markdown files as components and import them elsewhere, either in Markdown files or in React pages. Below we are importing from [another file](./markdown-features-intro.mdx) and inserting it as a component.
+You can use Markdown files as components and import them elsewhere, either in Markdown files or in React pages.
 
-```jsx
-import Intro from './markdown-features-intro.mdx';
+By convention, using the **`_` filename prefix** will not create any doc page and means the markdown file is a **"partial"**, to be imported by other files.
 
-<Intro />;
+```md title="_markdown-partial-example.mdx"
+<span>Hello {props.name}</span>
+
+This is text some content from `_markdown-partial-example.mdx`.
+```
+
+```jsx title="someOtherDoc.mdx"
+import PartialExample from './_markdown-partial-example.mdx';
+
+<PartialExample name="Sebastien" />;
 ```
 
 ```mdx-code-block
-import Intro from './markdown-features-intro.mdx';
+import PartialExample from './_markdown-partial-example.mdx';
 
 <BrowserWindow url="http://localhost:3000">
-
-<Intro />
-
+  <PartialExample name="Sebastien" />
 </BrowserWindow>
 
 <br />