Fix empty collections

Author: mythz

src/ServiceStack.Text/Common/DeserializeListWithElements.cs

@@ -110,8 +110,8 @@ public static List<string> ParseStringList(ReadOnlySpan<char> value)
 
         public static List<int> ParseIntList(ReadOnlySpan<char> value)
         {
-            if ((value = StripList(value)).IsEmpty) return null;
-            if (value.Length == 0) return new List<int>();
+            if ((value = StripList(value)).IsNullOrEmpty()) 
+                return value.IsEmpty ? null : new List<int>();
 
             var to = new List<int>();
             var valueLength = value.Length;
@@ -131,8 +131,8 @@ public static List<int> ParseIntList(ReadOnlySpan<char> value)
 
         public static List<byte> ParseByteList(ReadOnlySpan<char> value)
         {
-            if ((value = StripList(value)).IsEmpty) return null;
-            if (value.Length == 0) return new List<byte>();
+            if ((value = StripList(value)).IsNullOrEmpty()) 
+                return value.IsEmpty ? null : new List<byte>();
 
             var to = new List<byte>();
             var valueLength = value.Length;
@@ -161,7 +161,8 @@ public static ICollection<T> ParseGenericList(string value, Type createListType,
 
         public static ICollection<T> ParseGenericList(ReadOnlySpan<char> value, Type createListType, ParseStringSpanDelegate parseFn)
         {
-            if ((value = DeserializeListWithElements<TSerializer>.StripList(value)).IsEmpty) return null;
+            if ((value = DeserializeListWithElements<TSerializer>.StripList(value)).IsEmpty) 
+                return null;
 
             var isReadOnly = createListType != null
                 && (createListType.IsGenericType && createListType.GetGenericTypeDefinition() == typeof(ReadOnlyCollection<>));

src/ServiceStack.Text/PclExport.Net40.cs

@@ -683,10 +683,10 @@ public static Hashtable ParseHashtable(ReadOnlySpan<char> value)
 
         public static StringCollection ParseStringCollection<TS>(ReadOnlySpan<char> value) where TS : ITypeSerializer
         {
-            if ((value = DeserializeListWithElements<TS>.StripList(value)) == null) return null;
-            return value.Length == 0
-                   ? new StringCollection()
-                   : ToStringCollection(DeserializeListWithElements<TSerializer>.ParseStringList(value));
+            if ((value = DeserializeListWithElements<TS>.StripList(value)).IsNullOrEmpty()) 
+                return value.IsEmpty ? null : new StringCollection();
+    
+            return ToStringCollection(DeserializeListWithElements<TSerializer>.ParseStringList(value));
         }
 
         public static StringCollection ToStringCollection(List<string> items)

src/ServiceStack.Text/PclExport.NetStandard.cs

@@ -335,7 +335,8 @@ public override ParseStringSpanDelegate GetSpecializedCollectionParseStringSpanM
 
         private static StringCollection ParseStringCollection<TSerializer>(ReadOnlySpan<char> value) where TSerializer : ITypeSerializer
         {
-            if ((value = DeserializeListWithElements<TSerializer>.StripList(value)).IsEmpty) return null;
+            if ((value = DeserializeListWithElements<TSerializer>.StripList(value)).IsNullOrEmpty()) 
+                return value.IsEmpty ? null : new StringCollection();
 
             var result = new StringCollection();
 

tests/ServiceStack.Text.Tests/BasicStringSerializerTests.cs

@@ -628,16 +628,19 @@ public class EmptyCollections
         {
             public string[] Strings { get; set; }
             public int[] Ints { get; set; }
+            public List<int> IntList { get; set; }
         }
 
         [Test]
         public void Can_deserialize_empty_array()
         {
             Assert.That("[]".FromJson<string[]>(), Is.EquivalentTo(new string[0]));
             Assert.That("[]".FromJson<int[]>(), Is.EquivalentTo(new int[0]));
+            Assert.That("[]".FromJson<List<int>>(), Is.EquivalentTo(new List<int>()));
 
             Assert.That("{\"Strings\":[]}".FromJson<EmptyCollections>().Strings, Is.EquivalentTo(new string[0]));
             Assert.That("{\"Ints\":[]}".FromJson<EmptyCollections>().Ints, Is.EquivalentTo(new int[0]));
+            Assert.That("{\"IntList\":[]}".FromJson<EmptyCollections>().IntList, Is.EquivalentTo(new List<int>()));
         }
     }
 }