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Dante DG
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Implemented option to account for array entry moves in ArrayDiff.
Before, when an array entry moved, it was always documented in the result as an add and a delete. Now, an add and delete of the same entry can be treated as a single operation: a move. This implements a feature that already exists in the original jsondiffpatch.
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3 files changed

+226
-81
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3 files changed

+226
-81
lines changed

‎Src/JsonDiffPatchDotNet.UnitTests/DiffUnitTests.cs‎

Lines changed: 87 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -193,6 +193,49 @@ public void Diff_EfficientArrayDiffDifferentHeadAdded_ValidDiff()
193193
Assert.IsNotNull(diff["0"]);
194194
}
195195

196+
[Test]
197+
public void Diff_EfficientArrayDiffTailMovedToHead_IgnoreMove_NoChange()
198+
{
199+
var jdp = new JsonDiffPatch(new Options { ArrayDiff = ArrayDiffMode.Efficient, DiffArrayOptions = new ArrayOptions { DetectMove = true, IncludeValueOnMove = false } });
200+
var left = JToken.Parse(@"[1,2,3,4,5,6,7,8,9,10]");
201+
var right = JToken.Parse(@"[4,1,2,3,7,5,6,8,10,9]");
202+
203+
var diff = jdp.Diff(left, right);
204+
205+
Assert.IsNull(diff);
206+
}
207+
208+
[Test]
209+
public void Diff_EfficientArrayDiffTailHeadMovedToTail_IncludeMove_ValidDiff()
210+
{
211+
var jdp = new JsonDiffPatch(new Options { ArrayDiff = ArrayDiffMode.Efficient, DiffArrayOptions = new ArrayOptions { DetectMove = true, IncludeValueOnMove = true } });
212+
var left = JToken.Parse(@"[1,2,3,4]");
213+
var right = JToken.Parse(@"[2,3,4,1]");
214+
215+
JObject diff = jdp.Diff(left, right) as JObject;
216+
217+
Assert.IsNotNull(diff);
218+
Assert.AreEqual(2, diff.Properties().Count());
219+
Assert.AreEqual(diff["_0"], JToken.Parse("['', 3, 3]"));
220+
}
221+
222+
[Test]
223+
public void Diff_EfficientArrayDiffWithComplexObjects_IncludeMove_ValidDiff()
224+
{
225+
var jdp = new JsonDiffPatch(new Options { ArrayDiff = ArrayDiffMode.Efficient, ObjectHash = (jObj) => jObj["Id"].Value<string>(), DiffArrayOptions = new ArrayOptions { DetectMove = true, IncludeValueOnMove = true } });
226+
//var jdp = new JsonDiffPatch(new Options { ArrayDiff = ArrayDiffMode.Efficient });
227+
var left = JToken.Parse(@"[{""Id"" : ""F12B21EF-F57D-4958-ADDC-A3F52EC25EC8"", ""p"":false}, {""Id"" : ""F12B21EF-F57D-4958-ADDC-A3F52EC25EC9"", ""p"":true}, {""Id"" : ""F12B21EF-F57D-4958-ADDC-A3F52EC25EC10"", ""p"":true}]");
228+
var right = JToken.Parse(@"[{""Id"" : ""F12B21EF-F57D-4958-ADDC-A3F52EC25EC10"", ""p"":false}, {""Id"" : ""F12B21EF-F57D-4958-ADDC-A3F52EC25EC8"", ""p"":true}, {""Id"" : ""F12B21EF-F57D-4958-ADDC-A3F52EC25EC9"", ""p"":true}]");
229+
230+
JObject diff = jdp.Diff(left, right) as JObject;
231+
232+
Assert.IsNotNull(diff);
233+
Assert.AreEqual(4, diff.Properties().Count());
234+
Assert.AreEqual(diff["_2"], JToken.Parse("['', 0, 3]"));
235+
Assert.AreEqual(diff["0"]["p"], JToken.Parse("[true, false]"));
236+
Assert.AreEqual(diff["1"]["p"], JToken.Parse("[false, true]"));
237+
}
238+
196239
[Test]
197240
public void Diff_EfficientArrayDiffDifferentTailAdded_ValidDiff()
198241
{
@@ -250,22 +293,6 @@ public void Diff_EfficientArrayDiffWithComplexObject_ValidDiff()
250293
Assert.AreEqual(4, diff.Properties().Count());
251294
}
252295

253-
[Test]
254-
public void Diff_EfficientArrayDiffWithComplexObjectHash_ValidDiff()
255-
{
256-
var jdp = new JsonDiffPatch(new Options { ArrayDiff = ArrayDiffMode.Efficient, ObjectHash = (jObj) => jObj["Id"].Value<string>() });
257-
var left = JToken.Parse(@"[{""Id"": ""22ff56c7-2307-414b-8a3a-9bf1cdba2095"",""city"":""São Paulo""},{""Id"":""3fca9cdb-dd9b-4b7c-afc1-587751e25bd6"",""city"":""abc""},{""Id"":""1fe6a0f9-3974-427f-81cb-6004748cb179"",""city"":""xyz""}]");
258-
var right = JToken.Parse(@"[{""Id"":""3fca9cdb-dd9b-4b7c-afc1-587751e25bd6"",""city"":""abc""},{""Id"":""1fe6a0f9-3974-427f-81cb-6004748cb179"",""city"":""xyz""}, {""Id"":""3fca9cdb-dd9b-4b7c-afc1-587751e25b44"",""city"":""new""}]");
259-
260-
JObject diff = jdp.Diff(left, right) as JObject;
261-
262-
Assert.IsNotNull(diff);
263-
Assert.AreEqual(3, diff.Properties().Count());
264-
Assert.IsNotNull(diff["_0"]);
265-
Assert.IsNotNull(diff["2"]);
266-
Assert.AreEqual(((JArray)diff["2"])[0].Value<string>("city"), "new");
267-
}
268-
269296
[Test]
270297
public void Diff_EfficientArrayDiffSameWithObject_NoDiff()
271298
{
@@ -313,6 +340,50 @@ public void Diff_EfficientArrayDiffHugeArrays_NoStackOverflow()
313340
Assert.That(JToken.DeepEquals(restored, right));
314341
}
315342

343+
[Test]
344+
public void Diff_EfficientArrayDiffHugeArrays_OnlyIgnoredMoves_NoStackOverflow()
345+
{
346+
const int arraySize = 1000;
347+
348+
Func<JToken> shuffledArrayFunc = () =>
349+
{
350+
Random rng = new Random();
351+
var builder = new StringBuilder("[");
352+
353+
var randomList = new List<int>();
354+
for (int i = 0; i < arraySize; i++)
355+
{
356+
randomList.Add(i);
357+
}
358+
359+
// Shuffle array
360+
int n = arraySize - 1;
361+
while (n > 1)
362+
{
363+
n--;
364+
int k = rng.Next(n + 1);
365+
int val = randomList[k];
366+
randomList[k] = randomList[n];
367+
randomList[n] = val;
368+
}
369+
370+
foreach (var i in randomList)
371+
{
372+
builder.Append($"{i},");
373+
}
374+
builder.Append("]");
375+
376+
return JToken.Parse(builder.ToString());
377+
};
378+
379+
var jdp = new JsonDiffPatch(new Options { ArrayDiff = ArrayDiffMode.Efficient, DiffArrayOptions = new ArrayOptions { DetectMove = true, IncludeValueOnMove = false } });
380+
var left = shuffledArrayFunc();
381+
var right = shuffledArrayFunc();
382+
383+
JToken diff = jdp.Diff(left, right);
384+
Assert.IsNull(diff);
385+
}
386+
316387
[Test]
317388
public void Diff_IntStringDiff_ValidPatch()
318389
{

‎Src/JsonDiffPatchDotNet/JsonDiffPatch.cs‎

Lines changed: 76 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,10 @@
11
using System;
22
using System.Collections.Generic;
3+
using System.Dynamic;
34
using System.Globalization;
45
using System.IO;
56
using System.Linq;
7+
using System.Xml.Linq;
68
using DiffMatchPatch;
79
using Newtonsoft.Json.Linq;
810

@@ -379,7 +381,8 @@ private JObject ArrayDiff(JArray left, JArray right)
379381
{
380382
var objectHash = this._options.ObjectHash;
381383
var itemMatch = new DefaultItemMatch(objectHash);
382-
var result = JObject.Parse(@"{ ""_t"": ""a"" }");
384+
385+
var result = JObject.Parse(@"{ ""_t"": ""a"" }");
383386

384387
int commonHead = 0;
385388
int commonTail = 0;
@@ -389,22 +392,20 @@ private JObject ArrayDiff(JArray left, JArray right)
389392

390393
var childContext = new List<JToken>();
391394

392-
// Find common head
393-
while (commonHead < left.Count
394-
&& commonHead < right.Count
395-
&& itemMatch.Match(left[commonHead], right[commonHead]))
396-
{
397-
var index = commonHead;
398-
var child = Diff(left[index], right[index]);
399-
if(child != null)
400-
{
401-
result[$"{index}"] = child;
402-
}
403-
commonHead++;
404-
}
395+
while (commonHead < left.Count
396+
&& commonHead < right.Count
397+
&& itemMatch.Match(left[commonHead], right[commonHead]))
398+
{
399+
var index = commonHead;
400+
var child = Diff(left[index], right[index]);
401+
if (child != null)
402+
{
403+
result[$"{index}"] = child;
404+
}
405+
commonHead++;
406+
}
405407

406-
// Find common tail
407-
while (commonTail + commonHead < left.Count
408+
while (commonTail + commonHead < left.Count
408409
&& commonTail + commonHead < right.Count
409410
&& itemMatch.Match(left[left.Count - 1 - commonTail], right[right.Count - 1 - commonTail]))
410411
{
@@ -428,35 +429,52 @@ private JObject ArrayDiff(JArray left, JArray right)
428429

429430
return result;
430431
}
432+
431433
if (commonHead + commonTail == right.Count)
432434
{
433435
// Trivial case, a block (1 or more consecutive items) was removed
434436
for (int index = commonHead; index < left.Count - commonTail; ++index)
435437
{
436-
if (result.ContainsKey(index.ToString()))
437-
{
438-
result.Remove(index.ToString());
439-
}
440-
result[$"_{index}"] = new JArray(left[index], 0, (int)DiffOperation.Deleted);
438+
if (result.ContainsKey(index.ToString()))
439+
{
440+
result.Remove(index.ToString());
441+
}
442+
443+
result[$"_{index}"] = new JArray(left[index], 0, (int)DiffOperation.Deleted);
441444
}
442445

443446
return result;
444447
}
445448

446-
// Complex Diff, find the LCS (Longest Common Subsequence)
447-
List<JToken> trimmedLeft = left.ToList().GetRange(commonHead, left.Count - commonTail - commonHead);
449+
// Keep track of items in the array that were deleted, as if they are added back,
450+
// they can be treated as moves
451+
Dictionary<object, int> deletes = new Dictionary<object, int>();
452+
453+
var comparer = new JTokenEqualityComparer();
454+
455+
// Complex Diff, find the LCS (Longest Common Subsequence)
456+
List<JToken> trimmedLeft = left.ToList().GetRange(commonHead, left.Count - commonTail - commonHead);
448457
List<JToken> trimmedRight = right.ToList().GetRange(commonHead, right.Count - commonTail - commonHead);
458+
449459
Lcs lcs = Lcs.Get(trimmedLeft, trimmedRight, itemMatch);
450460

451461
for (int index = commonHead; index < left.Count - commonTail; ++index)
452462
{
453463
if (lcs.Indices1.IndexOf(index - commonHead) < 0)
454464
{
455-
// Removed
456465
if (result.ContainsKey(index.ToString()))
457466
{
458467
result.Remove(index.ToString());
459468
}
469+
470+
// If handling moves, mark the delete
471+
if (_options.DiffArrayOptions.DetectMove)
472+
{
473+
var entryId = (objectHash == null || left[index].Type != JTokenType.Object) ? comparer.GetHashCode(left[index]) : objectHash.Invoke(left[index]);
474+
475+
deletes.Add(entryId, index);
476+
}
477+
460478
result[$"_{index}"] = new JArray(left[index], 0, (int)DiffOperation.Deleted);
461479
}
462480
}
@@ -465,10 +483,35 @@ private JObject ArrayDiff(JArray left, JArray right)
465483
{
466484
int indexRight = lcs.Indices2.IndexOf(index - commonHead);
467485

468-
if (indexRight < 0)
486+
if (indexRight < 0)
469487
{
470-
// Added
471-
result[$"{index}"] = new JArray(right[index]);
488+
// If handling moves, check to see if the entry was already marked as deleted
489+
var entryId = (objectHash == null || right[index].Type != JTokenType.Object) ? comparer.GetHashCode(right[index]) : objectHash.Invoke(right[index]);
490+
491+
if (_options.DiffArrayOptions.DetectMove && deletes.ContainsKey(entryId))
492+
{
493+
// If added and deleted, it was moved (though still potentially modified)
494+
var compareIndex = deletes[entryId];
495+
result.Remove("_" + compareIndex.ToString());
496+
497+
// Only include a move in final result if flag is set
498+
if (_options.DiffArrayOptions.IncludeValueOnMove)
499+
{
500+
result[$"_{compareIndex}"] = new JArray("", index, 3);
501+
}
502+
503+
JToken diff = Diff(left[compareIndex], right[index]);
504+
505+
if (diff != null)
506+
{
507+
result[$"{index}"] = diff;
508+
}
509+
}
510+
else
511+
{
512+
// Added
513+
result[$"{index}"] = new JArray(right[index]);
514+
}
472515
}
473516
else
474517
{
@@ -484,6 +527,12 @@ private JObject ArrayDiff(JArray left, JArray right)
484527
}
485528
}
486529

530+
if (JToken.DeepEquals(result, JObject.Parse(@"{ ""_t"": ""a"" }")))
531+
{
532+
// result is empty, so ignored moves were the only modifications
533+
return null;
534+
}
535+
487536
return result;
488537
}
489538

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