fix + simple tests

Author: hemnstill

YamlDotNet.Test/Serialization/DeserializerTest.cs

@@ -21,6 +21,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using FluentAssertions;
 using Xunit;
@@ -331,6 +332,42 @@ public void DeserializeWithoutDuplicateKeyChecking_YamlWithDuplicateKeys_DoesNot
             act = () => sut.Deserialize<Dictionary<string, Dictionary<string, string>>>(parser);
             act.ShouldNotThrow<YamlException>("Because duplicate key checking is not enabled");
         }
+        
+        [Fact]
+        public void MergingParserWithMergeObjectWithSequence_ShouldNotThrowException()
+        {
+            var yaml = @"
+base_level: &base 
+  tenant: 
+  - a1
+Level1: &Level1
+    <<: [*base]
+Level2: &Level2
+    <<: *Level1
+";
+            var mergingParserFailed = new MergingParser(new Parser(new StringReader(yaml)));
+            var deserializer = new DeserializerBuilder().Build();
+            Action act = () => deserializer.Deserialize(mergingParserFailed);
+            act.ShouldNotThrow<Exception>();
+        }
+        
+        [Fact]
+        public void MergingParserWithNestedSequence_ShouldNotThrowException()
+        {
+            var yaml = @"
+base_level: &base {}
+Level1: &Level1
+    <<: [*base]
+Level2: &Level2
+    <<: [*Level1]
+Level3:
+    <<: *Level2
+";
+            var mergingParserFailed = new MergingParser(new Parser(new StringReader(yaml)));
+            var deserializer = new DeserializerBuilder().Build();
+            Action act = () => deserializer.Deserialize(mergingParserFailed);
+            act.ShouldNotThrow<Exception>();
+        }
 
         public class Test
         {

YamlDotNet/Core/MergingParser.cs

@@ -140,7 +140,8 @@ private bool HandleSequence(LinkedListNode<ParsingEvent> node)
             var current = node;
             while (current != null)
             {
-                if (current.Value is SequenceEnd)
+                if (current.Value is SequenceEnd &&
+                    current.Value.Start.Line >= sequenceStart.Value.Start.Line)
                 {
                     events.MarkDeleted(current);
                     return true;