fix #657 - relative positions issue when using followUndoneDeletions=false

src/utils/RelativePosition.js

@@ -9,7 +9,7 @@ import {
   ContentType,
   followRedone,
   getItem,
-  ID, Doc, AbstractType // eslint-disable-line
+  StructStore, ID, Doc, AbstractType, // eslint-disable-line
 } from '../internals.js'
 
 import * as encoding from 'lib0/encoding'
@@ -256,6 +256,18 @@ export const readRelativePosition = decoder => {
  */
 export const decodeRelativePosition = uint8Array => readRelativePosition(decoding.createDecoder(uint8Array))
 
+/**
+ * @param {StructStore} store
+ * @param {ID} id
+ */
+const getItemWithOffset = (store, id) => {
+  const item = getItem(store, id)
+  const diff = id.clock - item.id.clock
+  return {
+    item, diff
+  }
+}
+
 /**
  * Transform a relative position to an absolute position.
  *
@@ -286,7 +298,7 @@ export const createAbsolutePositionFromRelativePosition = (rpos, doc, followUndo
     if (getState(store, rightID.client) <= rightID.clock) {
       return null
     }
-    const res = followUndoneDeletions ? followRedone(store, rightID) : { item: getItem(store, rightID), diff: 0 }
+    const res = followUndoneDeletions ? followRedone(store, rightID) : getItemWithOffset(store, rightID)
     const right = res.item
     if (!(right instanceof Item)) {
       return null

tests/relativePositions.tests.js

@@ -85,6 +85,26 @@ export const testRelativePositionCase6 = tc => {
   checkRelativePositions(ytext)
 }
 
+/**
+ * Testing https://github.com/yjs/yjs/issues/657
+ *
+ * @param {t.TestCase} tc
+ */
+export const testRelativePositionCase7 = tc => {
+  const docA = new Y.Doc()
+  const textA = docA.getText('text')
+  textA.insert(0, 'abcde')
+  // Create a relative position at index 2 in 'textA'
+  const relativePosition = Y.createRelativePositionFromTypeIndex(textA, 2)
+  // Verify that the absolutes positions on 'docA' are the same
+  const absolutePositionWithFollow =
+    Y.createAbsolutePositionFromRelativePosition(relativePosition, docA, true)
+  const absolutePositionWithoutFollow =
+    Y.createAbsolutePositionFromRelativePosition(relativePosition, docA, false)
+  t.assert(absolutePositionWithFollow?.index === 2)
+  t.assert(absolutePositionWithoutFollow?.index === 2)
+}
+
 /**
  * @param {t.TestCase} tc
  */