fix: prevent crash when applying Yjs update with invalid Slate path

.changeset/defensive-path-handling.md

@@ -0,0 +1,5 @@
+---
+"@slate-yjs/core": patch
+---
+
+Fix crash when applying Yjs update with invalid Slate path. When Yjs and Slate get out of sync (e.g. after paste/duplication), the editor now recovers by re-syncing from Yjs instead of throwing "Cannot find a descendant at path".

.github/workflows/deploy.yml

@@ -11,10 +11,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Setup Node
-        uses: actions/setup-node@v2
+        uses: actions/setup-node@v4
         with:
           cache: yarn
           node-version-file: '.nvmrc'
@@ -40,22 +40,22 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Login to Docker Hub
-        uses: docker/login-action@v1
+        uses: docker/login-action@v3
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
       - name: Extract metadata (tags, labels) for Docker
         id: meta
-        uses: docker/metadata-action@v3
+        uses: docker/metadata-action@v5
         with:
           images: bitphinix/slate-yjs-example-backend
 
       - name: Build and push Docker image
-        uses: docker/build-push-action@v2
+        uses: docker/build-push-action@v5
         with:
           context: .
           file: ./examples/backend/Dockerfile

.github/workflows/lint.yml

@@ -14,12 +14,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
       - name: Setup Node
-        uses: actions/setup-node@v2
+        uses: actions/setup-node@v4
         with:
           cache: yarn
           node-version-file: '.nvmrc'

.github/workflows/release.yml

@@ -13,12 +13,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout Repo
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
       - name: Setup Node
-        uses: actions/setup-node@v2
+        uses: actions/setup-node@v4
         with:
           cache: yarn
           node-version-file: '.nvmrc'

.github/workflows/test.yml

@@ -14,12 +14,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
       - name: Setup Node
-        uses: actions/setup-node@v2
+        uses: actions/setup-node@v4
         with:
           cache: yarn
           node-version-file: '.nvmrc'

.nvmrc

@@ -1 +1 @@
-lts/gallium
+lts/iron

packages/core/src/applyToSlate/index.ts

@@ -1,7 +1,17 @@
-import { Editor, Operation } from 'slate';
+import { Editor, Operation, Transforms } from 'slate';
 import * as Y from 'yjs';
+import { RelativeRange } from '../model/types';
+import { yTextToSlateElement } from '../utils/convert';
+import { isSyncSkewError } from '../utils/errors';
+import {
+  relativeRangeToSlateRange,
+  slateRangeToRelativeRange,
+} from '../utils/position';
 import { translateYTextEvent } from './textEvent';
 
+let lastResyncTime = 0;
+const RESYNC_THROTTLE_MS = 1000;
+
 /**
  * Translate a yjs event into slate operations. The editor state has to match the
  * yText state before the event occurred.
@@ -21,10 +31,52 @@
   throw new Error('Unexpected Y event type');
 }
 
+/**
+ * Performs a full re-sync of the Slate editor from the Yjs shared root.
+ * Preserves the user's selection if possible by converting to/from relative positions.
+ */
+function resyncFromYjs(sharedRoot: Y.XmlText, editor: Editor): void {
+  let savedSelection: RelativeRange | null = null;
+
+  try {
+    if (editor.selection) {
+      savedSelection = slateRangeToRelativeRange(
+        sharedRoot,
+        editor,
+        editor.selection
+      );
+    }
+  } catch {
+    // Selection conversion failed; we'll lose the selection but continue with re-sync
+  }
+
+  const content = yTextToSlateElement(sharedRoot);
+  editor.children = content.children;
+  Editor.normalize(editor, { force: true });
+
+  if (savedSelection) {
+    try {
+      const newSelection = relativeRangeToSlateRange(
+        sharedRoot,
+        editor,
+        savedSelection
+      );
+      if (newSelection) {
+        Transforms.select(editor, newSelection);
+      }
+    } catch {
+      // Selection restoration failed; cursor position is lost but document is correct
+    }
+  }
+}
+
 /**
  * Translates yjs events into slate operations and applies them to the editor. The
  * editor state has to match the yText state before the events occurred.
  *
+ * If a sync-skew error occurs (e.g. invalid path due to Yjs/Slate mismatch),
+ * the editor is re-synced from the Yjs shared root to recover gracefully.
+ *
  * @param sharedRoot
  * @param editor
  * @param events
@@ -35,10 +87,32 @@
   events: Y.YEvent<Y.XmlText>[]
 ) {
   Editor.withoutNormalizing(editor, () => {
-    events.forEach((event) => {
-      translateYjsEvent(sharedRoot, editor, event).forEach((op) => {
-        editor.apply(op);
-      });
-    });
+    for (const event of events) {
+      try {
+        const ops = translateYjsEvent(sharedRoot, editor, event);
+        for (const op of ops) {
+          editor.apply(op);
+        }
+      } catch (error) {
+        if (isSyncSkewError(error)) {
+          const now = Date.now();
+          if (now - lastResyncTime >= RESYNC_THROTTLE_MS) {
+            lastResyncTime = now;
+            console.warn(
+              '[slate-yjs] Sync skew detected, re-syncing from Yjs:',
+              error instanceof Error ? error.message : error
+            );
+            resyncFromYjs(sharedRoot, editor);
+          } else {
+            console.warn(
+              '[slate-yjs] Sync skew detected (throttled, skipping re-sync):',
+              error instanceof Error ? error.message : error
+            );
+          }
+          return;
+        }
+        throw error;
+      }
+    }
   });
 }

packages/core/src/utils/errors.ts

@@ -0,0 +1,20 @@
+const SYNC_SKEW_ERROR_PATTERNS = [
+  'Cannot find a descendant at path',
+  'yOffset out of bounds',
+  'Cannot descent into slate text',
+  "yText isn't a descendant of root element",
+  "Path doesn't match yText",
+  'Unexpected y parent type',
+  'Path has to a have a length >= 1',
+  'yTarget spans multiple nodes',
+];
+
+export function isSyncSkewError(error: unknown): boolean {
+  if (!(error instanceof Error)) {
+    return false;
+  }
+
+  return SYNC_SKEW_ERROR_PATTERNS.some((pattern) =>
+    error.message.includes(pattern)
+  );
+}

packages/core/src/utils/position.ts

@@ -2,6 +2,7 @@ import { BasePoint, BaseRange, Node, Text } from 'slate';
 import * as Y from 'yjs';
 import { InsertDelta, RelativeRange, TextRange } from '../model/types';
 import { getInsertDeltaLength, yTextToInsertDelta } from './delta';
+import { isSyncSkewError } from './errors';
 import { getSlatePath, getYTarget, yOffsetToSlateOffsets } from './location';
 import { assertDocumentAttachment } from './yjs';
 
@@ -41,25 +42,30 @@ export function absolutePositionToSlatePoint(
     throw new Error('Absolute position points to a non-XMLText');
   }
 
-  const parentPath = getSlatePath(sharedRoot, slateRoot, type);
-  const parent = Node.get(slateRoot, parentPath);
+  try {
+    const parentPath = getSlatePath(sharedRoot, slateRoot, type);
+    const parent = Node.get(slateRoot, parentPath);
 
-  if (Text.isText(parent)) {
-    throw new Error(
-      "Absolute position doesn't match slateRoot, cannot descent into text"
-    );
-  }
+    if (Text.isText(parent)) {
+      return null;
+    }
 
-  const [pathOffset, textOffset] = yOffsetToSlateOffsets(parent, index, {
-    assoc,
-  });
+    const [pathOffset, textOffset] = yOffsetToSlateOffsets(parent, index, {
+      assoc,
+    });
 
-  const target = parent.children[pathOffset];
-  if (!Text.isText(target)) {
-    return null;
-  }
+    const target = parent.children[pathOffset];
+    if (!Text.isText(target)) {
+      return null;
+    }
 
-  return { path: [...parentPath, pathOffset], offset: textOffset };
+    return { path: [...parentPath, pathOffset], offset: textOffset };
+  } catch (error) {
+    if (isSyncSkewError(error)) {
+      return null;
+    }
+    throw error;
+  }
 }
 
 export function relativePositionToSlatePoint(