From bc1e3dacdadaed0072a69ebb6e630a79c50b7980 Mon Sep 17 00:00:00 2001
From: Eric Mc Sween <5454374+emcsween@users.noreply.github.com>
Date: Wed, 6 Nov 2024 08:09:13 -0500
Subject: [PATCH] Merge pull request #21643 from
 overleaf/em-tracked-deletes-at-same-position

Improve handling of tracked delete rejections

GitOrigin-RevId: 79308539f5e7af70f6292a0fd6352e882eac84dd
---
 libraries/ranges-tracker/index.cjs            | 31 ++++++++++----
 .../test/unit/ranges-tracker-test.js          | 42 +++++++++++++++++++
 2 files changed, 66 insertions(+), 7 deletions(-)

diff --git a/libraries/ranges-tracker/index.cjs b/libraries/ranges-tracker/index.cjs
index 8d3cb840c0..1311763020 100644
--- a/libraries/ranges-tracker/index.cjs
+++ b/libraries/ranges-tracker/index.cjs
@@ -313,10 +313,11 @@ class RangesTracker {
 
     let alreadyMerged = false
     let previousChange = null
+    let trackedDeleteRejected = false
     const movedChanges = []
     const removeChanges = []
     const newChanges = []
-
+    const trackedDeletesAtOpPosition = []
     for (let i = 0; i < this.changes.length; i++) {
       change = this.changes[i]
       const changeStart = change.op.p
@@ -327,13 +328,22 @@ class RangesTracker {
           change.op.p += opLength
           movedChanges.push(change)
         } else if (opStart === changeStart) {
-          // If we are undoing, then we want to cancel any existing delete ranges if we can.
-          // Check if the insert matches the start of the delete, and just remove it from the delete instead if so.
-          if (
+          // Keep track of tracked deletes that are at the same position as the
+          // insert. At the end of the loop, If we didn't find a tracked delete
+          // to reject, we'll move these deletes after the insert.
+          trackedDeletesAtOpPosition.push(change)
+
+          if (trackedDeleteRejected) {
+            // We rejected a tracked delete. Move the remaining tracked deletes after the insert
+            change.op.p += opLength
+            movedChanges.push(change)
+          } else if (
             undoing &&
             change.op.d.length >= op.i.length &&
             change.op.d.slice(0, op.i.length) === op.i
           ) {
+            // If we are undoing, then we want to reject any existing tracked delete if we can.
+            // Check if the insert matches the start of the delete, and just remove it from the delete instead if so.
             change.op.d = change.op.d.slice(op.i.length)
             change.op.p += op.i.length
             if (change.op.d === '') {
@@ -342,9 +352,7 @@ class RangesTracker {
               movedChanges.push(change)
             }
             alreadyMerged = true
-          } else {
-            change.op.p += opLength
-            movedChanges.push(change)
+            trackedDeleteRejected = true
           }
         }
       } else if (change.op.i != null) {
@@ -449,6 +457,15 @@ class RangesTracker {
       previousChange = change
     }
 
+    if (!trackedDeleteRejected) {
+      // We didn't reject any tracked delete. Move all existing tracked deletes
+      // at the insert position after the insert
+      for (const change of trackedDeletesAtOpPosition) {
+        change.op.p += opLength
+        movedChanges.push(change)
+      }
+    }
+
     if (this.track_changes && !alreadyMerged) {
       this._addOp(op, metadata)
     }
diff --git a/libraries/ranges-tracker/test/unit/ranges-tracker-test.js b/libraries/ranges-tracker/test/unit/ranges-tracker-test.js
index 75d7024d09..41c9b72697 100644
--- a/libraries/ranges-tracker/test/unit/ranges-tracker-test.js
+++ b/libraries/ranges-tracker/test/unit/ranges-tracker-test.js
@@ -4,6 +4,7 @@ const RangesTracker = require('../..')
 describe('RangesTracker', function () {
   describe('with duplicate change ids', function () {
     beforeEach(function () {
+      this.comments = []
       this.changes = [
         { id: 'id1', op: { p: 1, i: 'hello' } },
         { id: 'id2', op: { p: 10, i: 'world' } },
@@ -26,4 +27,45 @@ describe('RangesTracker', function () {
       expect(this.rangesTracker.changes).to.deep.equal([this.changes[2]])
     })
   })
+
+  describe('with multiple tracked deletes at the same position', function () {
+    beforeEach(function () {
+      this.comments = []
+      this.changes = [
+        { id: 'id1', op: { p: 33, d: 'before' } },
+        { id: 'id2', op: { p: 50, d: 'right before' } },
+        { id: 'id3', op: { p: 50, d: 'this one' } },
+        { id: 'id4', op: { p: 50, d: 'right after' } },
+        { id: 'id5', op: { p: 75, d: 'long after' } },
+      ]
+      this.rangesTracker = new RangesTracker(this.changes, this.comments)
+    })
+
+    it('preserves the text order when rejecting changes', function () {
+      this.rangesTracker.applyOp(
+        { p: 50, i: 'this one', u: true },
+        { user_id: 'user-id' }
+      )
+      expect(this.rangesTracker.changes).to.deep.equal([
+        { id: 'id1', op: { p: 33, d: 'before' } },
+        { id: 'id2', op: { p: 50, d: 'right before' } },
+        { id: 'id4', op: { p: 58, d: 'right after' } },
+        { id: 'id5', op: { p: 83, d: 'long after' } },
+      ])
+    })
+
+    it('moves all tracked deletes after the insert if not rejecting changes', function () {
+      this.rangesTracker.applyOp(
+        { p: 50, i: 'some other text', u: true },
+        { user_id: 'user-id' }
+      )
+      expect(this.rangesTracker.changes).to.deep.equal([
+        { id: 'id1', op: { p: 33, d: 'before' } },
+        { id: 'id2', op: { p: 65, d: 'right before' } },
+        { id: 'id3', op: { p: 65, d: 'this one' } },
+        { id: 'id4', op: { p: 65, d: 'right after' } },
+        { id: 'id5', op: { p: 90, d: 'long after' } },
+      ])
+    })
+  })
 })