SF-2905 Fix crash when syncing a book with invalid chapters (#2660)

src/SIL.XForge.Scripture/Services/DeltaUsxMapper.cs

@@ -549,6 +549,11 @@ public XDocument ToUsx(XDocument oldUsxDoc, IEnumerable<ChapterDelta> chapterDel
                     }
                 }
 
+                if (i >= chapterDeltaArray.Length)
+                {
+                    return newUsxDoc;
+                }
+
                 if (
                     chapterDeltaArray[i].Number == curChapter
                     && chapterDeltaArray[i].IsValid

test/SIL.XForge.Scripture.Tests/Services/DeltaUsxMapperTests.cs

@@ -119,6 +119,47 @@ public void ToUsx_EmptySegments()
         Assert.IsTrue(XNode.DeepEquals(newUsxDoc, expected));
     }
 
+    [Test]
+    public void ToUsx_InvalidChapters()
+    {
+        // Set up a USX document with two invalid chapters
+        XDocument usxDoc = Usx(
+            "RUT",
+            null,
+            "3.0",
+            Chapter("1"),
+            Verse("1"),
+            Chapter("2."),
+            Verse("1"),
+            Chapter("3"),
+            Verse("1"),
+            Chapter("4."),
+            Verse("1")
+        );
+
+        var mapper = new DeltaUsxMapper(_mapperGuidService, _logger, _exceptionHandler);
+
+        // Get the chapter deltas, which will be the valid chapters
+        List<ChapterDelta> chapterDeltas = mapper.ToChapterDeltas(usxDoc).ToList();
+
+        var expected1 = Delta.New().InsertChapter("1").InsertVerse("1").InsertBlank("verse_1_1").InsertText("\n");
+        var expected2 = Delta.New().InsertChapter("3").InsertVerse("1").InsertBlank("verse_3_1").InsertText("\n");
+
+        Assert.That(chapterDeltas[0].Number, Is.EqualTo(1));
+        Assert.That(chapterDeltas[0].LastVerse, Is.EqualTo(1));
+        Assert.That(chapterDeltas[0].IsValid, Is.True);
+        Assert.IsTrue(chapterDeltas[0].Delta.DeepEquals(expected1));
+
+        Assert.That(chapterDeltas[1].Number, Is.EqualTo(3));
+        Assert.That(chapterDeltas[1].LastVerse, Is.EqualTo(1));
+        Assert.That(chapterDeltas[1].IsValid, Is.True);
+        Assert.IsTrue(chapterDeltas[1].Delta.DeepEquals(expected2));
+
+        // Ensure that the USX round trips perfectly
+        XDocument newUsxDoc = mapper.ToUsx(usxDoc, chapterDeltas);
+        Assert.IsTrue(XNode.DeepEquals(newUsxDoc, usxDoc));
+    }
+
     [Test]
     public void ToUsx_CharText()
     {
@@ -1223,37 +1264,6 @@ public void ToUsx_MismatchNoChapters_UnchangedUsx()
             .ReportException(Arg.Is<Exception>((Exception e) => e.Message.Contains("no real chapters")));
     }
 
-    [Test]
-    public void ToUsx_MismatchedChapters_UnchangedUsx()
-    {
-        _exceptionHandler.ClearReceivedCalls();
-        var chapterDeltas = new[]
-        {
-            new ChapterDelta(
-                1,
-                0,
-                true,
-                new Delta().InsertChapter("1").InsertBlank("p_1").InsertVerse("1").InsertBlank("verse_1_1")
-            )
-        };
-
-        var mapper = new DeltaUsxMapper(_mapperGuidService, _logger, _exceptionHandler);
-
-        // The USX here has chapter 2, which is not in chapterDeltas. The chapterDeltas does contain 1 real chapter.
-        XDocument input = Usx(
-            "PHM",
-            Chapter("1"),
-            Para("p", Verse("1"), "Verse text."),
-            Chapter("2"),
-            Para("p", Verse("1"), "Verse text.")
-        );
-
-        // SUT
-        Exception thrown = Assert.Throws<Exception>(() => mapper.ToUsx(input, chapterDeltas));
-        Assert.That(thrown.Message, Contains.Substring("Rethrowing"));
-        Assert.That(thrown.InnerException, Is.TypeOf<IndexOutOfRangeException>());
-    }
-
     [Test]
     public void ToUsx_BlankLine()
     {
@@ -3605,8 +3615,8 @@ public void Roundtrip_NestedChars()
         AssertRoundtrips(
             """
 \id PHM
-\c 1
-\p
+            \c 1
+            \p
 \v 1 \bd \+sup 1\+sup* This is\+sup 2\+sup* bold text.\+sup 3\+sup* \bd*  This is normal text.
 """
         );