refactor(theme-classic): split CodeBlock (#7175)

* extract CodeBlockLine

* stable refactor

* stable refactor

* stable refactor

* add CodeBlockContainer

* refactor

* refactor

* do the actual split

Co-authored-by: Joshua Chen <sidachen2003@gmail.com>

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

@@ -148,10 +148,10 @@ declare module '@theme/BlogLayout' {
 }
 
 declare module '@theme/CodeBlock' {
-  import type {ReactElement} from 'react';
+  import type {ReactNode} from 'react';
 
   export interface Props {
-    readonly children: string | ReactElement;
+    readonly children: ReactNode;
     readonly className?: string;
     readonly metastring?: string;
     readonly title?: string;
@@ -170,6 +170,56 @@ declare module '@theme/CodeBlock/CopyButton' {
   export default function CopyButton(props: Props): JSX.Element;
 }
 
+declare module '@theme/CodeBlock/Container' {
+  import type {ComponentProps} from 'react';
+
+  export default function CodeBlockContainer<T extends 'div' | 'pre'>({
+    as: As,
+    ...props
+  }: {as: T} & ComponentProps<T>): JSX.Element;
+}
+
+declare module '@theme/CodeBlock/Content/Element' {
+  import type {Props} from '@theme/CodeBlock';
+
+  export type {Props};
+
+  export default function CodeBlockElementContent(props: Props): JSX.Element;
+}
+
+declare module '@theme/CodeBlock/Content/String' {
+  import type {Props as CodeBlockProps} from '@theme/CodeBlock';
+
+  export interface Props extends Omit<CodeBlockProps, 'children'> {
+    readonly children: string;
+  }
+
+  export default function CodeBlockStringContent(props: Props): JSX.Element;
+}
+
+declare module '@theme/CodeBlock/Line' {
+  import type {ComponentProps} from 'react';
+  import type Highlight from 'prism-react-renderer';
+
+  // Lib does not make this easy
+  type RenderProps = Parameters<
+    ComponentProps<typeof Highlight>['children']
+  >[0];
+  type GetLineProps = RenderProps['getLineProps'];
+  type GetTokenProps = RenderProps['getTokenProps'];
+  type Token = RenderProps['tokens'][number][number];
+
+  export interface Props {
+    readonly line: Token[];
+    readonly highlight: boolean;
+    readonly showLineNumbers: boolean;
+    readonly getLineProps: GetLineProps;
+    readonly getTokenProps: GetTokenProps;
+  }
+
+  export default function CodeBlockLine(props: Props): JSX.Element;
+}
+
 declare module '@theme/DocCard' {
   import type {PropSidebarItem} from '@docusaurus/plugin-content-docs';
 

packages/docusaurus-theme-classic/src/theme/CodeBlock/Container/index.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, {type ComponentProps} from 'react';
+import clsx from 'clsx';
+import {
+  usePrismTheme,
+  getPrismCssVariables,
+  ThemeClassNames,
+} from '@docusaurus/theme-common';
+import styles from './styles.module.css';
+
+export default function CodeBlockContainer<T extends 'div' | 'pre'>({
+  as: As,
+  ...props
+}: {as: T} & ComponentProps<T>): JSX.Element {
+  const prismTheme = usePrismTheme();
+  const prismCssVariables = getPrismCssVariables(prismTheme);
+  return (
+    <As
+      // Polymorphic components are hard to type, without `oneOf` generics
+      {...(props as never)}
+      style={prismCssVariables}
+      className={clsx(
+        props.className,
+        styles.codeBlockContainer,
+        ThemeClassNames.common.codeBlock,
+      )}
+    />
+  );
+}

packages/docusaurus-theme-classic/src/theme/CodeBlock/Container/styles.module.css

@@ -0,0 +1,14 @@
+/**
+ * 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.
+ */
+
+.codeBlockContainer {
+  background: var(--prism-background-color);
+  color: var(--prism-color);
+  margin-bottom: var(--ifm-leading);
+  box-shadow: var(--ifm-global-shadow-lw);
+  border-radius: var(--ifm-code-border-radius);
+}

packages/docusaurus-theme-classic/src/theme/CodeBlock/Content/Element.tsx

@@ -0,0 +1,30 @@
+/**
+ * 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 Container from '@theme/CodeBlock/Container';
+import clsx from 'clsx';
+import type {Props} from '@theme/CodeBlock/Content/Element';
+
+import styles from './styles.module.css';
+
+// <pre> tags in markdown map to CodeBlocks. They may contain JSX children. When
+// the children is not a simple string, we just return a styled block without
+// actually highlighting.
+export default function CodeBlockJSX({
+  children,
+  className,
+}: Props): JSX.Element {
+  return (
+    <Container
+      as="pre"
+      tabIndex={0}
+      className={clsx(styles.codeBlockStandalone, 'thin-scrollbar', className)}>
+      <code className={styles.codeBlockLines}>{children}</code>
+    </Container>
+  );
+}

packages/docusaurus-theme-classic/src/theme/CodeBlock/Content/String.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 from 'react';
+import {
+  useThemeConfig,
+  parseCodeBlockTitle,
+  parseLanguage,
+  parseLines,
+  containsLineNumbers,
+  usePrismTheme,
+} from '@docusaurus/theme-common';
+import clsx from 'clsx';
+import Highlight, {defaultProps, type Language} from 'prism-react-renderer';
+import Line from '@theme/CodeBlock/Line';
+import CopyButton from '@theme/CodeBlock/CopyButton';
+import Container from '@theme/CodeBlock/Container';
+import type {Props} from '@theme/CodeBlock/Content/String';
+
+import styles from './styles.module.css';
+
+export default function CodeBlockString({
+  children,
+  className: blockClassName = '',
+  metastring,
+  title: titleProp,
+  showLineNumbers: showLineNumbersProp,
+  language: languageProp,
+}: Props): JSX.Element {
+  const {
+    prism: {defaultLanguage},
+  } = useThemeConfig();
+  const language =
+    languageProp ?? parseLanguage(blockClassName) ?? defaultLanguage;
+  const prismTheme = usePrismTheme();
+
+  // We still parse the metastring in case we want to support more syntax in the
+  // future. Note that MDX doesn't strip quotes when parsing metastring:
+  // "title=\"xyz\"" => title: "\"xyz\""
+  const title = parseCodeBlockTitle(metastring) || titleProp;
+
+  const {highlightLines, code} = parseLines(children, metastring, language);
+  const showLineNumbers =
+    showLineNumbersProp || containsLineNumbers(metastring);
+
+  return (
+    <Container
+      as="div"
+      className={clsx(
+        blockClassName,
+        language &&
+          !blockClassName.includes(`language-${language}`) &&
+          `language-${language}`,
+      )}>
+      {title && <div className={styles.codeBlockTitle}>{title}</div>}
+      <div className={styles.codeBlockContent}>
+        <Highlight
+          {...defaultProps}
+          theme={prismTheme}
+          code={code}
+          language={(language ?? 'text') as Language}>
+          {({className, tokens, getLineProps, getTokenProps}) => (
+            <pre
+              /* eslint-disable-next-line jsx-a11y/no-noninteractive-tabindex */
+              tabIndex={0}
+              className={clsx(className, styles.codeBlock, 'thin-scrollbar')}>
+              <code
+                className={clsx(
+                  styles.codeBlockLines,
+                  showLineNumbers && styles.codeBlockLinesWithNumbering,
+                )}>
+                {tokens.map((line, i) => (
+                  <Line
+                    key={i}
+                    line={line}
+                    getLineProps={getLineProps}
+                    getTokenProps={getTokenProps}
+                    highlight={highlightLines.includes(i)}
+                    showLineNumbers={showLineNumbers}
+                  />
+                ))}
+              </code>
+            </pre>
+          )}
+        </Highlight>
+        <CopyButton code={code} />
+      </div>
+    </Container>
+  );
+}

packages/docusaurus-theme-classic/src/theme/CodeBlock/Content/styles.module.css

@@ -5,14 +5,6 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-.codeBlockContainer {
-  background: var(--prism-background-color);
-  color: var(--prism-color);
-  margin-bottom: var(--ifm-leading);
-  box-shadow: var(--ifm-global-shadow-lw);
-  border-radius: var(--ifm-code-border-radius);
-}
-
 .codeBlockContent {
   position: relative;
   /* rtl:ignore */
@@ -62,31 +54,3 @@
     white-space: pre-wrap;
   }
 }
-
-.codeLine {
-  display: table-row;
-  counter-increment: line-count;
-}
-
-.codeLineNumber {
-  display: table-cell;
-  text-align: right;
-  width: 1%;
-  position: sticky;
-  left: 0;
-  padding: 0 var(--ifm-pre-padding);
-  background: var(--ifm-pre-background);
-}
-
-.codeLineNumber::before {
-  content: counter(line-count);
-  opacity: 0.4;
-}
-
-:global(.docusaurus-highlight-code-line) .codeLineNumber::before {
-  opacity: 0.8;
-}
-
-.codeLineContent {
-  padding-right: var(--ifm-pre-padding);
-}

packages/docusaurus-theme-classic/src/theme/CodeBlock/Line/index.tsx

@@ -0,0 +1,51 @@
+/**
+ * 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/CodeBlock/Line';
+import styles from './styles.module.css';
+
+export default function CodeBlockLine({
+  line,
+  highlight,
+  showLineNumbers,
+  getLineProps,
+  getTokenProps,
+}: Props): JSX.Element {
+  if (line.length === 1 && line[0]!.content === '\n') {
+    line[0]!.content = '';
+  }
+
+  const lineProps = getLineProps({
+    line,
+    ...(showLineNumbers && {className: styles.codeLine}),
+  });
+
+  if (highlight) {
+    lineProps.className += ' docusaurus-highlight-code-line';
+  }
+
+  const lineTokens = line.map((token, key) => (
+    <span key={key} {...getTokenProps({token, key})} />
+  ));
+
+  return (
+    <span {...lineProps}>
+      {showLineNumbers ? (
+        <>
+          <span className={styles.codeLineNumber} />
+          <span className={styles.codeLineContent}>{lineTokens}</span>
+        </>
+      ) : (
+        <>
+          {lineTokens}
+          <br />
+        </>
+      )}
+    </span>
+  );
+}

packages/docusaurus-theme-classic/src/theme/CodeBlock/Line/styles.module.css

@@ -0,0 +1,34 @@
+/**
+ * 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.
+ */
+
+.codeLine {
+  display: table-row;
+  counter-increment: line-count;
+}
+
+.codeLineNumber {
+  display: table-cell;
+  text-align: right;
+  width: 1%;
+  position: sticky;
+  left: 0;
+  padding: 0 var(--ifm-pre-padding);
+  background: var(--ifm-pre-background);
+}
+
+.codeLineNumber::before {
+  content: counter(line-count);
+  opacity: 0.4;
+}
+
+:global(.docusaurus-highlight-code-line) .codeLineNumber::before {
+  opacity: 0.8;
+}
+
+.codeLineContent {
+  padding-right: var(--ifm-pre-padding);
+}

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

@@ -5,172 +5,41 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import React, {isValidElement, useEffect, useState} from 'react';
-import clsx from 'clsx';
-import Highlight, {defaultProps, type Language} from 'prism-react-renderer';
-import {
-  useThemeConfig,
-  parseCodeBlockTitle,
-  parseLanguage,
-  parseLines,
-  containsLineNumbers,
-  ThemeClassNames,
-  usePrismTheme,
-  getPrismCssVariables,
-} from '@docusaurus/theme-common';
-import CopyButton from '@theme/CodeBlock/CopyButton';
+import React, {isValidElement, type ReactNode} from 'react';
+import useIsBrowser from '@docusaurus/useIsBrowser';
 import type {Props} from '@theme/CodeBlock';
+import ElementContent from '@theme/CodeBlock/Content/Element';
+import StringContent from '@theme/CodeBlock/Content/String';
 
-import styles from './styles.module.css';
+/**
+ * Best attempt to make the children a plain string so it is copyable. If there
+ * are react elements, we will not be able to copy the content, and it will
+ * return `children` as-is; otherwise, it concatenates the string children
+ * together.
+ */
+function maybeStringifyChildren(children: ReactNode): ReactNode {
+  if (React.Children.toArray(children).some((el) => isValidElement(el))) {
+    return children;
+  }
+  // The children is now guaranteed to be one/more plain strings
+  return Array.isArray(children) ? children.join('') : (children as string);
+}
 
 export default function CodeBlock({
-  children,
-  className: blockClassName = '',
-  metastring,
-  title,
-  showLineNumbers,
-  language: languageProp,
+  children: rawChildren,
+  ...props
 }: Props): JSX.Element {
-  const {prism} = useThemeConfig();
-
-  const [mounted, setMounted] = useState(false);
-  // The Prism theme on SSR is always the default theme but the site theme
-  // can be in a different mode. React hydration doesn't update DOM styles
-  // that come from SSR. Hence force a re-render after mounting to apply the
-  // current relevant styles. There will be a flash seen of the original
-  // styles seen using this current approach but that's probably ok. Fixing
-  // the flash will require changing the theming approach and is not worth it
-  // at this point.
-  useEffect(() => {
-    setMounted(true);
-  }, []);
-
-  // We still parse the metastring in case we want to support more syntax in the
-  // future. Note that MDX doesn't strip quotes when parsing metastring:
-  // "title=\"xyz\"" => title: "\"xyz\""
-  const codeBlockTitle = parseCodeBlockTitle(metastring) || title;
-  const prismTheme = usePrismTheme();
-
-  const prismCssVariables = getPrismCssVariables(prismTheme);
-
-  // <pre> tags in markdown map to CodeBlocks and they may contain JSX children.
-  // When the children is not a simple string, we just return a styled block
-  // without actually highlighting.
-  if (React.Children.toArray(children).some((el) => isValidElement(el))) {
-    return (
-      <Highlight
-        {...defaultProps}
-        key={String(mounted)}
-        theme={prismTheme}
-        code=""
-        language={'text' as Language}>
-        {({className}) => (
-          <pre
-            /* eslint-disable-next-line jsx-a11y/no-noninteractive-tabindex */
-            tabIndex={0}
-            className={clsx(
-              className,
-              styles.codeBlockStandalone,
-              'thin-scrollbar',
-              styles.codeBlockContainer,
-              blockClassName,
-              ThemeClassNames.common.codeBlock,
-            )}
-            style={prismCssVariables}>
-            <code className={styles.codeBlockLines}>{children}</code>
-          </pre>
-        )}
-      </Highlight>
-    );
-  }
-
-  // The children is now guaranteed to be one/more plain strings
-  const content = Array.isArray(children)
-    ? children.join('')
-    : (children as string);
-
-  const language =
-    languageProp ?? parseLanguage(blockClassName) ?? prism.defaultLanguage;
-  const {highlightLines, code} = parseLines(content, metastring, language);
-  const shouldShowLineNumbers =
-    showLineNumbers || containsLineNumbers(metastring);
-
+  // The Prism theme on SSR is always the default theme but the site theme can
+  // be in a different mode. React hydration doesn't update DOM styles that come
+  // from SSR. Hence force a re-render after mounting to apply the current
+  // relevant styles.
+  const isBrowser = useIsBrowser();
+  const children = maybeStringifyChildren(rawChildren);
+  const CodeBlockComp =
+    typeof children === 'string' ? StringContent : ElementContent;
   return (
-    <Highlight
-      {...defaultProps}
-      key={String(mounted)}
-      theme={prismTheme}
-      code={code}
-      language={(language ?? 'text') as Language}>
-      {({className, tokens, getLineProps, getTokenProps}) => (
-        <div
-          className={clsx(
-            styles.codeBlockContainer,
-            blockClassName,
-            {
-              [`language-${language}`]:
-                language && !blockClassName.includes(`language-${language}`),
-            },
-            ThemeClassNames.common.codeBlock,
-          )}
-          style={prismCssVariables}>
-          {codeBlockTitle && (
-            <div className={styles.codeBlockTitle}>{codeBlockTitle}</div>
-          )}
-          <div className={styles.codeBlockContent}>
-            <pre
-              /* eslint-disable-next-line jsx-a11y/no-noninteractive-tabindex */
-              tabIndex={0}
-              className={clsx(className, styles.codeBlock, 'thin-scrollbar')}>
-              <code
-                className={clsx(
-                  styles.codeBlockLines,
-                  shouldShowLineNumbers && styles.codeBlockLinesWithNumbering,
-                )}>
-                {tokens.map((line, i) => {
-                  if (line.length === 1 && line[0]!.content === '\n') {
-                    line[0]!.content = '';
-                  }
-
-                  const lineProps = getLineProps({
-                    line,
-                    key: i,
-                    ...(shouldShowLineNumbers && {className: styles.codeLine}),
-                  });
-
-                  if (highlightLines.includes(i)) {
-                    lineProps.className += ' docusaurus-highlight-code-line';
-                  }
-
-                  const lineTokens = line.map((token, key) => (
-                    <span key={key} {...getTokenProps({token, key})} />
-                  ));
-
-                  return (
-                    <span key={i} {...lineProps}>
-                      {shouldShowLineNumbers ? (
-                        <>
-                          <span className={styles.codeLineNumber} />
-                          <span className={styles.codeLineContent}>
-                            {lineTokens}
-                          </span>
-                        </>
-                      ) : (
-                        <>
-                          {lineTokens}
-                          <br />
-                        </>
-                      )}
-                    </span>
-                  );
-                })}
-              </code>
-            </pre>
-
-            <CopyButton code={code} />
-          </div>
-        </div>
-      )}
-    </Highlight>
+    <CodeBlockComp key={String(isBrowser)} {...props}>
+      {children as string}
+    </CodeBlockComp>
   );
 }

packages/docusaurus-theme-common/src/utils/codeBlockUtils.ts

@@ -182,11 +182,10 @@ export function getPrismCssVariables(prismTheme: PrismTheme): CSSProperties {
     backgroundColor: '--prism-background-color',
   };
 
-  const properties: CSSProperties = {};
+  const properties: {[key: string]: string} = {};
   Object.entries(prismTheme.plain).forEach(([key, value]) => {
     const varName = mapping[key];
     if (varName && typeof value === 'string') {
-      // @ts-expect-error: why css variables not in inline style type?
       properties[varName] = value;
     }
   });