Set the target to data of the last stage

Sources/Algorithm.swift

@@ -95,6 +95,12 @@ public extension StagedChangeset where Collection: RangeReplaceableCollection, C
  )
  }
 
+ // Set the target to `data` of the last stage.
+ if !changesets.isEmpty {
+ let index = changesets.index(before: changesets.endIndex)
+ changesets[index].data = target
+ }
+
  self.init(changesets)
  }
 }
@@ -363,6 +369,12 @@ public extension StagedChangeset where Collection: RangeReplaceableCollection, C
  )
  }
 
+ // Set the target to `data` of the last stage.
+ if !changesets.isEmpty {
+ let index = changesets.index(before: changesets.endIndex)
+ changesets[index].data = target
+ }
+
  self.init(changesets)
  }
 }

Tests/AlgorithmTest.swift

@@ -5,6 +5,18 @@ final class AlgorithmTestCase: XCTestCase {}
 
 /// Test algorithm for linear collection.
 extension AlgorithmTestCase {
+ func testEmptyChangesets() {
+ let source = [Int]()
+ let target = [Int]()
+
+ XCTAssertExactDifferences(
+ source: source,
+ target: target,
+ section: 0,
+ expected: []
+ )
+ }
+
  func testDeleted() {
  let section = 1
 
@@ -227,6 +239,17 @@ extension AlgorithmTestCase {
 
 /// Test algorithm for sectioned collection.
 extension AlgorithmTestCase {
+ func testSectionedEmptyChangesets() {
+ let source = [Section<Int, Int>]()
+ let target = [Section<Int, Int>]()
+
+ XCTAssertExactDifferences(
+ source: source,
+ target: target,
+ expected: []
+ )
+ }
+
  func testSectionInserted() {
  let source1 = [
  Section(model: D.a, elements: [0])