Include element updates in changet stage 4

Sources/Algorithm.swift

@@ -253,8 +253,8 @@ public extension StagedChangeset where Collection: RangeReplaceableCollection, C
  // If the element target section is recorded as insertion, record its element path as deletion.
  if let targetElementPath = sourceElementTraces[sourceElementPath].reference,
  case .some = sectionResult.metadata.targetReferences[targetElementPath.section] {
- let targetElement = contiguousTargetSections[targetElementPath]
- firstStageElements.append(targetElement)
+ let sourceElement = contiguousSourceSections[sourceElementPath]
+ firstStageElements.append(sourceElement)
  continue
  }
 
@@ -263,8 +263,8 @@ public extension StagedChangeset where Collection: RangeReplaceableCollection, C
  offsetByDelete += 1
  }
 
- let section = Section(source: sourceSections[sourceSectionIndex], elements: firstStageElements)
- firstStageSections.append(section)
+ let firstStageSection = Section(source: sourceSections[sourceSectionIndex], elements: firstStageElements)
+ firstStageSections.append(firstStageSection)
  }
 
  // Record the element updates/moves/insertions.
@@ -284,30 +284,32 @@ public extension StagedChangeset where Collection: RangeReplaceableCollection, C
  let secondStageSection = firstStageSections[sourceSectionIndex - sectionDeleteOffset]
  secondStageSections.append(secondStageSection)
 
- let thirdStageSection = Section(source: secondStageSection, elements: targetElements)
- thirdStageSections.append(thirdStageSection)
+ var thirdStageElements = ContiguousArray<Element>()
+ thirdStageElements.reserveCapacity(targetElements.count)
 
  for targetElementIndex in targetElements.indices {
  untrackedSourceIndex = untrackedSourceIndex.flatMap { index in
  sourceElementTraces[sourceSectionIndex].suffix(from: index).index { !$0.isTracked }
  }
 
  let targetElementPath = ElementPath(element: targetElementIndex, section: targetSectionIndex)
+ let targetElement = contiguousTargetSections[targetElementPath]
 
  // If the element source section is recorded as deletion, record its element path as insertion.
  guard let sourceElementPath = targetElementReferences[targetElementPath],
  let movedSourceSectionIndex = sectionResult.metadata.sourceTraces[sourceElementPath.section].reference else {
+ thirdStageElements.append(targetElement)
  elementInserted.append(targetElementPath)
  continue
  }
 
  sourceElementTraces[sourceElementPath].isTracked = true
 
  let sourceElement = contiguousSourceSections[sourceElementPath]
- let targetElement = contiguousTargetSections[targetElementPath]
+ thirdStageElements.append(sourceElement)
 
  if !targetElement.isContentEqual(to: sourceElement) {
- elementUpdated.append(sourceElementPath)
+ elementUpdated.append(targetElementPath)
  }
 
  if sourceElementPath.section != sourceSectionIndex || sourceElementPath.element != untrackedSourceIndex {
@@ -316,19 +318,21 @@ public extension StagedChangeset where Collection: RangeReplaceableCollection, C
  elementMoved.append((source: moveSourceElementPath, target: targetElementPath))
  }
  }
+
+ let thirdStageSection = Section(source: secondStageSection, elements: thirdStageElements)
+ thirdStageSections.append(thirdStageSection)
  }
 
  var changesets = ContiguousArray<Changeset<Collection>>()
 
- // The 1st stage changeset includes only the section deletions and element deletions, element updates
- // and the collection that its changes applied to source collection.
- if !sectionResult.deleted.isEmpty || !elementDeleted.isEmpty || !elementUpdated.isEmpty {
+ // The 1st stage changeset includes only the section deletions and element deletions and the collection
+ // that its changes applied to source collection.
+ if !sectionResult.deleted.isEmpty || !elementDeleted.isEmpty {
  changesets.append(
  Changeset(
  data: Collection(firstStageSections),
  sectionDeleted: sectionResult.deleted,
- elementDeleted: elementDeleted,
- elementUpdated: elementUpdated
+ elementDeleted: elementDeleted
  )
  )
  }
@@ -358,11 +362,12 @@ public extension StagedChangeset where Collection: RangeReplaceableCollection, C
  }
 
  // The 4th stage changeset includes only the section updates and the collection that its changes applied to 3rd stage collection.
- if !sectionResult.updated.isEmpty {
+ if !sectionResult.updated.isEmpty || !elementUpdated.isEmpty {
  changesets.append(
  Changeset(
  data: target,
- sectionUpdated: sectionResult.updated
+ sectionUpdated: sectionResult.updated,
+ elementUpdated: elementUpdated
  )
  )
  }