Merge pull request #22650 from overleaf/em-tracked-deletes-at-same-position

Handle multiple tracked deletes at same position

GitOrigin-RevId: 3cbf1c418bcd50cf08e1b90ce6ba3bc480236079

services/document-updater/app/js/RangesManager.js

@@ -352,6 +352,12 @@ function getHistoryOpForInsert(op, comments, changes) {
     }
   }
 
+  // If it's determined that the op is a tracked delete rejection, we have to
+  // calculate its proper history position. If multiple tracked deletes are
+  // found at the same position as the insert, the tracked deletes that come
+  // before the tracked delete that was actually rejected offset the history
+  // position.
+  let trackedDeleteRejectionOffset = 0
   for (const change of changes) {
     if (!isDelete(change.op)) {
       // We're only interested in tracked deletes
@@ -362,14 +368,25 @@ function getHistoryOpForInsert(op, comments, changes) {
       // Tracked delete is before the op. Move the op forward.
       hpos += change.op.d.length
     } else if (change.op.p === op.p) {
-      // Tracked delete is at the same position as the op. The insert comes before
-      // the tracked delete so it doesn't move.
+      // Tracked delete is at the same position as the op.
       if (op.u && change.op.d.startsWith(op.i)) {
         // We're undoing and the insert matches the start of the tracked
         // delete. RangesManager treats this as a tracked delete rejection. We
         // will note this in the op so that project-history can take the
         // appropriate action.
         trackedDeleteRejection = true
+
+        // The history must be updated to take into account all preceding
+        // tracked deletes at the same position
+        hpos += trackedDeleteRejectionOffset
+
+        // No need to continue. All subsequent tracked deletes are after the
+        // insert.
+        break
+      } else {
+        // This tracked delete does not match the insert. Note its length in
+        // case we find a tracked delete that matches later.
+        trackedDeleteRejectionOffset += change.op.d.length
       }
     } else {
       // Tracked delete is after the insert. Tracked deletes are ordered, so

services/document-updater/test/unit/js/RangesManager/RangesManagerTests.js

@@ -323,6 +323,44 @@ describe('RangesManager', function () {
         })
       })
 
+      describe('tracked delete rejections with multiple tracked deletes at the same position', function () {
+        beforeEach(function () {
+          // original text is "one [two ][three ][four ]five"
+          // [] denotes tracked deletes
+          this.ranges = {
+            changes: makeRanges([
+              { d: 'two ', p: 4 },
+              { d: 'three ', p: 4 },
+              { d: 'four ', p: 4 },
+            ]),
+          }
+          this.updates = makeUpdates([{ i: 'three ', p: 4, u: true }])
+          this.newDocLines = ['one three five']
+          this.result = this.RangesManager.applyUpdate(
+            this.project_id,
+            this.doc_id,
+            this.ranges,
+            this.updates,
+            this.newDocLines,
+            { historyRangesSupport: true }
+          )
+        })
+
+        it('should insert the text at the right history position', function () {
+          expect(this.result.historyUpdates.map(x => x.op)).to.deep.equal([
+            [
+              {
+                i: 'three ',
+                p: 4,
+                hpos: 8,
+                u: true,
+                trackedDeleteRejection: true,
+              },
+            ],
+          ])
+        })
+      })
+
       describe('deletes over tracked changes', function () {
         beforeEach(function () {
           // original text is "on[1]e [22](three) f[333]ou[4444]r [55555]five"