Workaround Docusaurus prism highlighting hydration bug (#1519)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1519

See https://github.com/facebook/docusaurus/issues/9629

We use prism to render the code for the inline editor. Prism renders colors to style directly, and the color chosen is dependent on a setting that may not be available at SSR time.

This adds an SSR-specific representation of the code, missing some of the nuances in token colorization (similar to https://github.com/facebook/docusaurus/pull/7373). This adds a little bit of jank compared to perfect SSR, but fixes cases where the mode is incorrect, and is a lot less jank then the more generic solution used by theme-live-codeblock of keeping the rendering of the opposite color until rehydration.

Preview: https://yoga-website-next-git-fork-nickgerleman-exp-2f8171-fbopensource.vercel.app/

Reviewed By: yungsters

Differential Revision: D52163722

fbshipit-source-id: 312dc52134f0084d40f78147190151700ee10ff7

website-next/src/components/Playground.module.css

@@ -9,12 +9,16 @@ html[data-theme='light'] {
   --yg-color-preview-background: var(--ifm-color-primary-lighter);
   --yg-color-playground-background: var(--ifm-color-gray-200);
   --yg-color-editor-border: var(--ifm-color-gray-400);
+  --yg-color-editor-fallback-bg: rgb(246, 248, 250);
+  --yg-color-editor-fallback-text: rgb(0, 0, 159);
 }
 
 html[data-theme='dark'] {
   --yg-color-preview-background: var(--ifm-color-primary-dark);
   --yg-color-playground-background: var(--ifm-color-background);
   --yg-color-editor-border: var(--ifm-color-gray-800);
+  --yg-color-editor-fallback-bg: rgb(40, 44, 52);
+  --yg-color-editor-fallback-text: rgb(209, 154, 102);
 }
 
 .wrapper {
@@ -47,8 +51,8 @@ html[data-theme='dark'] {
 
 .editorToolbar {
   position: absolute;
-  top: 10px;
+  top: var(--ifm-pre-padding);
-  right: 10px;
+  right: var(--ifm-pre-padding);
 }
 
 .playgroundEditor {
@@ -62,6 +66,12 @@ html[data-theme='dark'] {
   box-shadow: var(--ifm-global-shadow-lw);
   min-height: 100%;
   border-radius: 0;
+  padding: var(--ifm-pre-padding) !important;
+}
+
+.liveEditorFallback {
+  background-color: var(--yg-color-editor-fallback-bg);
+  color: var(--yg-color-editor-fallback-text);
 }
 
 .previewColumn {

website-next/src/components/Playground.tsx

@@ -27,6 +27,7 @@ import type {FlexStyle} from './FlexStyle';
 import type {StyleNode} from './YogaViewer';
 
 import styles from './Playground.module.css';
+import useIsBrowser from '@docusaurus/useIsBrowser';
 
 export type Props = Readonly<{
   code: string;
@@ -37,6 +38,7 @@ export type Props = Readonly<{
 export default function Playground({code, height, autoFocus}: Props) {
   const prismTheme = usePrismTheme();
   const editorScrollRef = useRef<HTMLDivElement>(null);
+  const isBrowser = useIsBrowser();
 
   const [liveCode, setLiveCode] = useState(code);
   const [hasCodeChanged, setHasCodeChanged] = useState(false);
@@ -72,6 +74,11 @@ export default function Playground({code, height, autoFocus}: Props) {
     ? ({'--yg-playground-height': height} as React.CSSProperties)
     : undefined;
 
+  const handleCodeChange = useCallback((code: string) => {
+    setHasCodeChanged(true);
+    setLiveCode(code);
+  }, []);
+
   return (
     <LiveProvider
       code={liveCode}
@@ -86,13 +93,15 @@ export default function Playground({code, height, autoFocus}: Props) {
                 className={styles.editorToolbar}
                 style={{paddingRight: scrollbarWidth + 'px'}}
               />
+
+              {isBrowser ? (
                 <LiveEditor
                   className={clsx(styles.playgroundEditor)}
-                onChange={useCallback((code: string) => {
+                  onChange={handleCodeChange}
-                  setHasCodeChanged(true);
-                  setLiveCode(code);
-                }, [])}
                 />
+              ) : (
+                <LiveEditorFallback code={liveCode} />
+              )}
             </div>
           </div>
           <div className={clsx(styles.previewColumn)}>
@@ -105,6 +114,21 @@ export default function Playground({code, height, autoFocus}: Props) {
   );
 }
 
+/**
+ * Provides a non-editable approximation of the LiveEditor result, without
+ * relying on prism rendering, for use during SSR.
+ * See https://github.com/facebook/docusaurus/issues/9629
+ */
+function LiveEditorFallback({code}: Readonly<{code: string}>) {
+  return (
+    <div className={clsx(styles.playgroundEditor)}>
+      <pre className={clsx('prism-code', styles.liveEditorFallback)}>
+        {code}
+      </pre>
+    </div>
+  );
+}
+
 type RootLiveNodeProps = Readonly<{
   children: React.ReactNode;
   config?: {useWebDefaults?: boolean};