Fix StringCharMapping key order dependency

.changeset/great-buses-switch.md

@@ -0,0 +1,5 @@
+---
+"@udecode/plate-diff": patch
+---
+
+Fix: Node equivalency checking is incorrectly dependent on the key order of the node object

packages/diff/src/internal/utils/string-char-mapping.spec.ts

@@ -0,0 +1,10 @@
+import { StringCharMapping } from './string-char-mapping';
+
+describe('StringCharMapping', () => {
+  it('treats nodes as equivalent regardless of key order', () => {
+    const map = new StringCharMapping();
+    const c1 = map.nodeToChar({ type: 'a', children: [] });
+    const c2 = map.nodeToChar({ children: [], type: 'a' });
+    expect(c1).toBe(c2);
+  });
+});

packages/diff/src/internal/utils/string-char-mapping.ts

@@ -4,27 +4,28 @@
  */
 
 import { TDescendant } from '@udecode/plate-common';
+import isEqual from 'lodash/isEqual.js';
+
+import { unusedCharGenerator } from './unused-char-generator';
 
 export class StringCharMapping {
-  private _nextChar: string = 'A';
-  private _charToNode: Map<string, TDescendant> = new Map();
-  private _keyToChar: Map<string, string> = new Map();
+  private _charGenerator = unusedCharGenerator();
+  private _mappedNodes: [TDescendant, string][] = [];
 
   public nodesToString(nodes: TDescendant[]): string {
     return nodes.map(this.nodeToChar.bind(this)).join('');
   }
 
   public nodeToChar(node: TDescendant): string {
-    const key = this.getKeyForNode(node);
-
-    const existingChar = this._keyToChar.get(key);
-    if (existingChar) return existingChar;
-
-    const c = this.getNextChar();
-
-    this._keyToChar.set(key, c);
-    this._charToNode.set(c, node);
-
+    // Check for a previously assigned character
+    for (const [n, c] of this._mappedNodes) {
+      if (isEqual(n, node)) {
+        return c;
+      }
+    }
+
+    const c = this._charGenerator.next().value;
+    this._mappedNodes.push([node, c]);
     return c;
   }
 
@@ -33,18 +34,8 @@ export class StringCharMapping {
   }
 
   public charToNode(c: string): TDescendant {
-    const node = this._charToNode.get(c);
-    if (!node) throw new Error(`No node found for char ${c}`);
-    return node;
-  }
-
-  private getKeyForNode(node: TDescendant): string {
-    return JSON.stringify(node);
-  }
-
-  private getNextChar(): string {
-    const c = this._nextChar;
-    this._nextChar = String.fromCodePoint(this._nextChar.codePointAt(0)! + 1);
-    return c;
+    const entry = this._mappedNodes.find(([_node, c2]) => c2 === c);
+    if (!entry) throw new Error(`No node found for char ${c}`);
+    return entry[0];
   }
 }