Run <Slate />'s focus event listeners after <Editable />'s focus handlers in React >= 17 (#4920)

* use focusin and focusout without capture if react >= 17

See facebook/react#19186 for details on changes to `onFocus` and `onBlur`

* more accurate name for react version check const

* add changeset

* add comment about react >= 17 focus event listeners

Author: adri1wald

.changeset/five-emus-roll.md

@@ -0,0 +1,5 @@
+---
+'slate-react': patch
+---
+
+fix useFocused hook in react >= 17

packages/slate-react/src/components/slate.tsx

@@ -9,6 +9,7 @@ import {
   SlateSelectorContext,
 } from '../hooks/use-slate-selector'
 import { EDITOR_TO_ON_CHANGE } from '../utils/weak-maps'
+import { IS_REACT_VERSION_17_OR_ABOVE } from '../utils/environment'
 import { useIsomorphicLayoutEffect } from '../hooks/use-isomorphic-layout-effect'
 
 /**
@@ -73,16 +74,23 @@ export const Slate = (props: {
 
   useIsomorphicLayoutEffect(() => {
     const fn = () => setIsFocused(ReactEditor.isFocused(editor))
-    document.addEventListener('focus', fn, true)
-    return () => document.removeEventListener('focus', fn, true)
-  }, [])
-
-  useIsomorphicLayoutEffect(() => {
-    const fn = () => setIsFocused(ReactEditor.isFocused(editor))
-    document.addEventListener('blur', fn, true)
-    return () => {
-      document.removeEventListener('focus', fn, true)
-      document.removeEventListener('blur', fn, true)
+    if (IS_REACT_VERSION_17_OR_ABOVE) {
+      // In React >= 17 onFocus and onBlur listen to the focusin and focusout events during the bubbling phase.
+      // Therefore in order for <Editable />'s handlers to run first, which is necessary for ReactEditor.isFocused(editor)
+      // to return the correct value, we have to listen to the focusin and focusout events without useCapture here.
+      document.addEventListener('focusin', fn)
+      document.addEventListener('focusout', fn)
+      return () => {
+        document.removeEventListener('focusin', fn)
+        document.removeEventListener('focusout', fn)
+      }
+    } else {
+      document.addEventListener('focus', fn, true)
+      document.addEventListener('blur', fn, true)
+      return () => {
+        document.removeEventListener('focus', fn, true)
+        document.removeEventListener('blur', fn, true)
+      }
     }
   }, [])
 

packages/slate-react/src/utils/environment.ts

@@ -1,3 +1,8 @@
+import React from 'react'
+
+export const IS_REACT_VERSION_17_OR_ABOVE =
+  parseInt(React.version.split('.')[0], 10) >= 17
+
 export const IS_IOS =
   typeof navigator !== 'undefined' &&
   typeof window !== 'undefined' &&