From 2c88ecc63880c4c720436bb5609c442f21fea00d Mon Sep 17 00:00:00 2001
From: Martin Kamleithner <martin.kamleithner@gmail.com>
Date: Sat, 16 Dec 2023 18:54:39 +0100
Subject: [PATCH] potential fix: wrong postponed update calc (#22)

* potential fix: wrong postponed update calc

* add regression tests
---
 lib/src/diffutil_impl.dart   |  1 -
 test/diffutil_data_test.dart | 15 +++++++++++++++
 test/diffutil_test.dart      | 17 ++++++++++++++++-
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/lib/src/diffutil_impl.dart b/lib/src/diffutil_impl.dart
index fdd49b7..6a86c2a 100644
--- a/lib/src/diffutil_impl.dart
+++ b/lib/src/diffutil_impl.dart
@@ -554,7 +554,6 @@ class DiffResult<T> {
       if (update.posInOwnerList == posInList && update.removal == removal) {
         postponedUpdate = update;
         postponedUpdates.removeAt(i);
-        i++;
         break;
       }
       i++;
diff --git a/test/diffutil_data_test.dart b/test/diffutil_data_test.dart
index f9697f5..7652d4f 100644
--- a/test/diffutil_data_test.dart
+++ b/test/diffutil_data_test.dart
@@ -324,6 +324,21 @@ void main() {
         ],
       );
     });
+
+    test("github issue #21: move detection bug", () {
+      final start = [1, 2, 3, 4, 5, 6];
+      final end = [1, 4, 2, 5, 6, 3];
+
+      final updates = diffutil
+          .calculateListDiff(start, end, detectMoves: true)
+          .getUpdatesWithData()
+          .toList();
+
+      expect(updates, const [
+        DataMove(from: 2, to: 5, data: 3),
+        DataMove(from: 1, to: 2, data: 2),
+      ]);
+    });
   });
 }
 
diff --git a/test/diffutil_test.dart b/test/diffutil_test.dart
index 6506cb6..65e74e1 100644
--- a/test/diffutil_test.dart
+++ b/test/diffutil_test.dart
@@ -242,7 +242,7 @@ void main() {
     ]);
   });
 
-  group('test list result calculaction', () {
+  group('test list result calculation', () {
     test('insert works in result list', () {
       expect(
           diffutil
@@ -334,6 +334,21 @@ void main() {
       );
     });
   });
+
+  test("github issue #21: move detection bug", () {
+    final start = [1, 2, 3, 4, 5, 6];
+    final end = [1, 4, 2, 5, 6, 3];
+
+    final updates = diffutil
+        .calculateListDiff(start, end, detectMoves: true)
+        .getUpdates(batch: false)
+        .toList();
+
+    expect(updates, const [
+      Move(from: 2, to: 5),
+      Move(from: 1, to: 2),
+    ]);
+  });
 }
 
 class DataObjectListDiff extends diffutil.ListDiffDelegate<DataObject> {