chore: add shouldMergeNodesRemovePrevNode (#5621)

* chore: add shouldMergeNodesRemovePrevNode

* fix: typo

.changeset/early-mayflies-grow.md

@@ -0,0 +1,5 @@
+---
+'slate': minor
+---
+
+Add a `shouldMergeNodesRemovePrevNode` editor method to control when `Transforms.mergeNodes` should remove the previous node rather than carrying out a merge operation. 

packages/slate/src/create-editor.ts

@@ -57,6 +57,7 @@ import {
   rangeRef,
   rangeRefs,
   setNormalizing,
+  shouldMergeNodesRemovePrevNode,
   start,
   string,
   unhangRange,
@@ -181,6 +182,8 @@ export const createEditor = (): Editor => {
     void: (...args) => getVoid(editor, ...args),
     withoutNormalizing: (...args) => withoutNormalizing(editor, ...args),
     wrapNodes: (...args) => wrapNodes(editor, ...args),
+    shouldMergeNodesRemovePrevNode: (...args) =>
+      shouldMergeNodesRemovePrevNode(editor, ...args),
   }
 
   return editor

packages/slate/src/editor/index.ts

@@ -52,3 +52,4 @@ export * from './start'
 export * from './string'
 export * from './unhang-range'
 export * from './without-normalizing'
+export * from './should-merge-nodes-remove-prev-node'

packages/slate/src/editor/should-merge-nodes-remove-prev-node.ts

@@ -0,0 +1,17 @@
+import { EditorInterface, Element, Editor, Text } from '../interfaces'
+
+export const shouldMergeNodesRemovePrevNode: EditorInterface['shouldMergeNodesRemovePrevNode'] =
+  (editor, [prevNode, prevPath], [curNode, curNodePath]) => {
+    // If the target node that we're merging with is empty, remove it instead
+    // of merging the two. This is a common rich text editor behavior to
+    // prevent losing formatting when deleting entire nodes when you have a
+    // hanging selection.
+    // if prevNode is first child in parent,don't remove it.
+
+    return (
+      (Element.isElement(prevNode) && Editor.isEmpty(editor, prevNode)) ||
+      (Text.isText(prevNode) &&
+        prevNode.text === '' &&
+        prevPath[prevPath.length - 1] !== 0)
+    )
+  }

packages/slate/src/interfaces/editor.ts

@@ -167,6 +167,9 @@ export interface BaseEditor {
   string: OmitFirstArg<typeof Editor.string>
   unhangRange: OmitFirstArg<typeof Editor.unhangRange>
   void: OmitFirstArg<typeof Editor.void>
+  shouldMergeNodesRemovePrevNode: OmitFirstArg<
+    typeof Editor.shouldMergeNodesRemovePrevNode
+  >
 }
 
 export type Editor = ExtendedType<'Editor', BaseEditor>
@@ -709,6 +712,15 @@ export interface EditorInterface {
    * Call a function, deferring normalization until after it completes.
    */
   withoutNormalizing: (editor: Editor, fn: () => void) => void
+
+  /**
+   *  Call a function, Determine whether or not remove the previous node when merge.
+   */
+  shouldMergeNodesRemovePrevNode: (
+    editor: Editor,
+    prevNodeEntry: NodeEntry,
+    curNodeEntry: NodeEntry
+  ) => boolean
 }
 
 // eslint-disable-next-line no-redeclare
@@ -953,6 +965,9 @@ export const Editor: EditorInterface = {
   withoutNormalizing(editor, fn: () => void) {
     editor.withoutNormalizing(fn)
   },
+  shouldMergeNodesRemovePrevNode: (editor, prevNode, curNode) => {
+    return editor.shouldMergeNodesRemovePrevNode(prevNode, curNode)
+  },
 }
 
 /**

packages/slate/src/transforms-node/merge-nodes.ts

@@ -128,17 +128,7 @@ export const mergeNodes: NodeTransforms['mergeNodes'] = (
       Transforms.removeNodes(editor, { at: emptyRef.current!, voids })
     }
 
-    // If the target node that we're merging with is empty, remove it instead
-    // of merging the two. This is a common rich text editor behavior to
-    // prevent losing formatting when deleting entire nodes when you have a
-    // hanging selection.
-    // if prevNode is first child in parent,don't remove it.
-    if (
-      (Element.isElement(prevNode) && Editor.isEmpty(editor, prevNode)) ||
-      (Text.isText(prevNode) &&
-        prevNode.text === '' &&
-        prevPath[prevPath.length - 1] !== 0)
-    ) {
+    if (Editor.shouldMergeNodesRemovePrevNode(editor, prev, current)) {
       Transforms.removeNodes(editor, { at: prevPath, voids })
     } else {
       editor.apply({