FixXsdTimeSpanSerializeDeserialize

unit tests for serialize/deserialize negative timespans
fix TimeSpanConverter to handle negative timespans

Author: yuinlin

src/ServiceStack.Text/Support/TimeSpanConverter.cs

@@ -8,10 +8,11 @@ public class TimeSpanConverter
     {
         public static string ToXsdDuration(TimeSpan timeSpan)
         {
-            var sb = new StringBuilder("P");
+            var sb = new StringBuilder();
 
-            double ticks = timeSpan.Ticks;
+            sb.Append(timeSpan.Ticks < 0 ? "-P" : "P");
 
+            double ticks = Math.Abs(timeSpan.Ticks);
             double totalSeconds = ticks / TimeSpan.TicksPerSecond;
             int wholeSeconds = (int) totalSeconds;
             int seconds = wholeSeconds;
@@ -55,6 +56,7 @@ public static TimeSpan FromXsdDuration(string xsdDuration)
             int hours = 0;
             int minutes = 0;
             double seconds = 0;
+            var sign = (xsdDuration.StartsWith("-", StringComparison.Ordinal) ? -1 : 1);
 
             string[] t = xsdDuration.Substring(1).SplitOnFirst('T'); //strip P
 
@@ -100,7 +102,7 @@ public static TimeSpan FromXsdDuration(string xsdDuration)
                     + (minutes * 60)
                     + (seconds);
 
-            var interval = (long) (totalSecs * TimeSpan.TicksPerSecond);
+            var interval = (long) (totalSecs * TimeSpan.TicksPerSecond * sign);
 
             return TimeSpan.FromTicks(interval);
         }

tests/ServiceStack.Text.Tests/DateTimeOffsetAndTimeSpanTests.cs

@@ -59,6 +59,26 @@ public void Can_serialize_TimeSpan_field()
             Serialize(model);
         }
 
+        [Test]
+        public void Can_serialize_negative_TimeSpan_field()
+        {
+            var period = new TimeSpan(0, 0, -15, 0);
+
+            var model = new SampleModel { Id = 1, TimeSpan = period };
+            var json = JsonSerializer.SerializeToString(model);
+            Assert.That(json, Is.StringContaining("\"TimeSpan\":\"-PT15M\""));
+        }
+
+        [Test]
+        public void Can_deserialize_negative_TimeSpan_string()
+        {
+            var expectedTimeSpan = new TimeSpan(0, 0, -15, 0);
+            const string timeSpanString = @"-PT15M";
+
+            var timeSpan = JsonSerializer.DeserializeFromString<TimeSpan>(timeSpanString);
+            Assert.That(timeSpan, Is.EqualTo(expectedTimeSpan));
+        }
+
         [Test]
         public void Can_serialize_TimeSpan_field_with_StandardTimeSpanFormat()
         {