Recyclable.AddRange fixed to ignore empty sources

Recyclable.Collections/RecyclableList.cs

@@ -275,6 +275,11 @@ namespace Recyclable.Collections
 
 		public void AddRange(in T[] items)
 		{
+			if (items.LongLength == 0)
+			{
+				return;
+			}
+
 			long targetCapacity = _longCount + items.LongLength;
 			if (_capacity < targetCapacity)
 			{
@@ -309,6 +314,11 @@ namespace Recyclable.Collections
 
 		public void AddRange(RecyclableArrayList<T> items)
 		{
+			if (items.Count == 0)
+			{
+				return;
+			}
+
 			long targetCapacity = _longCount + items.Count;
 			if (_capacity < targetCapacity)
 			{
@@ -343,6 +353,11 @@ namespace Recyclable.Collections
 
 		public void AddRange(RecyclableList<T> items)
 		{
+			if (items.LongCount == 0)
+			{
+				return;
+			}
+
 			long itemsCount = items.LongCount,
 				targetCapacity = _longCount + itemsCount;
 
@@ -410,6 +425,11 @@ namespace Recyclable.Collections
 
 		public void AddRange(List<T> items)
 		{
+			if (items.Count == 0)
+			{
+				return;
+			}
+
 			long targetCapacity = _longCount + items.Count;
 			if (_capacity < targetCapacity)
 			{
@@ -445,6 +465,11 @@ namespace Recyclable.Collections
 
 		public void AddRange(IList<T> items)
 		{
+			if (items.Count == 0)
+			{
+				return;
+			}
+
 			long targetCapacity = _longCount + items.Count;
 			if (_capacity < targetCapacity)
 			{

Recyclable.CollectionsTests/EnumerableWithoutCount.cs

@@ -0,0 +1,17 @@
+using System.Collections;
+
+namespace Recyclable.CollectionsTests
+{
+	public class EnumerableWithoutCount<T> : IEnumerable<T>
+	{
+		private IEnumerable<T> _testData;
+
+		public EnumerableWithoutCount(IEnumerable<T> testData)
+		{
+			_testData = testData;
+		}
+
+		public IEnumerator<T> GetEnumerator() => _testData.GetEnumerator();
+		IEnumerator IEnumerable.GetEnumerator() => _testData.GetEnumerator();
+	}
+}

Recyclable.CollectionsTests/RecyclableListTests.cs

@@ -323,6 +323,17 @@ namespace Recyclable.CollectionsTests
 			new object[] { "IEnumerable<int>", _testData },
 		};
 
+		public static IEnumerable<object[]> AddRangeEmptyCollectionTypes => new[]
+		{
+			new object[] { "int[]", Array.Empty<int>() },
+			new object[] { "List<int>", Array.Empty<int>().ToList() },
+			new object[] { "RecyclableArrayList<int>", Array.Empty<int>().ToRecyclableArrayList() },
+			new object[] { "RecyclableList<int>", Array.Empty<int>().ToRecyclableList() },
+			new object[] { "IList<int>", new CustomIList<int>(Array.Empty<int>()) },
+			new object[] { "IEnumerable<int> with non-enumerated count", Array.Empty<int>().AsEnumerable() },
+			new object[] { "IEnumerable<int> without non-enumerated count", new EnumerableWithoutCount<int>(Array.Empty<int>()) }
+		};
+
 		[Theory]
 		[MemberData(nameof(AddRangeCollectionTypes))]
 		public void AddRangeShouldAddItemsInCorrectOrder(string testCase, IEnumerable<int> testData)
@@ -428,6 +439,48 @@ namespace Recyclable.CollectionsTests
 				.And.BeEquivalentTo(expectedData);
 		}
 
+		[Theory]
+		[MemberData(nameof(AddRangeEmptyCollectionTypes))]
+		public void AddRangeShouldDoNothingWhenSourceIsEmpty(string testCase, IEnumerable<int> testData)
+		{
+			// Prepare
+			var list = new RecyclableList<int>();
+
+			// Act
+			if (testData is int[] testDataArray)
+			{
+				list.AddRange(testDataArray);
+			}
+			else if (testData is List<int> testDataList)
+			{
+				list.AddRange(testDataList);
+			}
+			else if (testData is RecyclableArrayList<int> testDataRecyclableArrayList)
+			{
+				list.AddRange(testDataRecyclableArrayList);
+			}
+			else if (testData is RecyclableList<int> testDataRecyclableList)
+			{
+				list.AddRange(testDataRecyclableList);
+			}
+			else if (testData is IList<int> testDataIList)
+			{
+				list.AddRange(testDataIList);
+			}
+			else if (testData is IEnumerable<int> testDataIEnumerable)
+			{
+				list.AddRange(testDataIEnumerable);
+			}
+			else
+			{
+				throw new InvalidCastException("Unknown type of test data");
+			}
+
+			// Validate
+			_ = list.Capacity.Should().Be(0);
+			_ = list.Should().BeEmpty().And.HaveCount(0);
+		}
+
 		[Fact]
 		public void InsertAtTheBeginningShouldMoveItems()
 		{