fix diff issue

Author: dmonad

delta/delta.js

@@ -1075,10 +1075,12 @@ export class Delta {
     }
     while (currNode != null && currNode.length <= remainingLen) {
       list.pushEnd(cpy.children, currNode.clone())
+      remainingLen -= currNode.length
       currNode = currNode.next
     }
     if (currNode != null && remainingLen > 0) {
       list.pushEnd(cpy.children, currNode.clone(0, remainingLen))
+      remainingLen -= math.min(currNode.length, remainingLen)
     }
     cpy.childCnt = slicedLen - remainingLen
     // @ts-ignore
@@ -2247,11 +2249,12 @@ export const diff = (d1, d2) => {
           const cd = cdiff[i]
           cd.remove = isContent.slice(cd.index, cd.index + cd.remove.length)
           cd.insert = shouldContent.slice(cd.index + adj, cd.index + adj + cd.insert.length)
-          adj += cd.remove.length - cd.insert.length
+          adj += cd.insert.length - cd.remove.length
         }
         for (let i = 0, lastIndex = 0; i < cdiff.length; i++) {
           const cd = cdiff[i]
           d.retain(cd.index - lastIndex)
+          lastIndex = cd.index
           let cdii = 0
           let cdri = 0
           // try to match as much content as possible, preferring to skip over non-deltas

delta/delta.test.js

@@ -710,3 +710,13 @@ export const testDeltaDiffWithFormatting2 = () => {
   const diff = delta.diff(d1, d2)
   t.compare(diff, delta.create().retain(5).insert(' ').insert('world', { bold: true }))
 }
+
+export const testDeltaDiffIssue1 = () => {
+  const stateA = delta.create().insert([delta.create('paragraph').set('ychange', null).insert('ABCDEFGHIJKLMNOPQRSTUVWXYZ')])
+  const stateB = delta.create().insert([delta.create('paragraph').set('ychange', null).insert('ABCDE123FGHIJKLMNOPQRSTUVWXYZ2sawfa')])
+  const expectedDiff = delta.create().modify(delta.create().retain(5).insert('123').retain(21).insert('2sawfa'))
+  const diffResult = delta.diff(stateA, stateB)
+  const synced = delta.clone(stateA).apply(diffResult)
+  t.assert(synced.equals(stateB))
+  t.assert(expectedDiff.equals(diffResult))
+}