fix(react): useEditor should not destroy still mounted instances (#5338)

This forces the editor to re-use the editor instance that existed prior to an unmount and remount of the same component.
This fixes a bug in `React.StrictMode` introduced with the latest performance updates by PR #5161

.changeset/clever-mice-search.md

@@ -0,0 +1,5 @@
+---
+"@tiptap/react": patch
+---
+
+Fixes strict mode accidentally destroying the editor instance

demos/src/Examples/Performance/React/index.jsx

@@ -93,7 +93,7 @@ function EditorInstance({ shouldOptimizeRendering }) {
   )
 }
 
-export default () => {
+const EditorControls = () => {
   const [shouldOptimizeRendering, setShouldOptimizeRendering] = React.useState(true)
 
   return (
@@ -128,3 +128,11 @@ export default () => {
     </>
   )
 }
+
+export default () => {
+  return (
+    <React.StrictMode>
+      <EditorControls />
+    </React.StrictMode>
+  )
+}

packages/react/src/useEditor.ts

@@ -57,6 +57,7 @@ export function useEditor(
   options: UseEditorOptions = {},
   deps: DependencyList = [],
 ): Editor | null {
+  const isMounted = useRef(false)
   const [editor, setEditor] = useState(() => {
     if (options.immediatelyRender === undefined) {
       if (isSSR || isNext) {
@@ -220,12 +221,21 @@ export function useEditor(
    * only be called when the component is removed from the DOM, since it has no deps.
    * */
   useEffect(() => {
+    isMounted.current = true
     return () => {
+      isMounted.current = false
       if (editor) {
         // We need to destroy the editor asynchronously to avoid memory leaks
         // because the editor instance is still being used in the component.
 
-        setTimeout(() => (editor.isDestroyed ? null : editor.destroy()))
+        setTimeout(() => {
+          // re-use the editor instance if it hasn't been destroyed yet
+          // and the component is still mounted
+          // otherwise, asynchronously destroy the editor instance
+          if (!isMounted.current && !editor.isDestroyed) {
+            editor.destroy()
+          }
+        })
       }
     }
   }, [])