Fix parsed decimal losing trailing zeroes (#2769)

Author: JamesNK

Src/Newtonsoft.Json.Tests/Issues/Issue2768.cs

@@ -0,0 +1,151 @@
+#region License
+// Copyright (c) 2007 James Newton-King
+//
+// Permission is hereby granted, free of charge, to any person
+// obtaining a copy of this software and associated documentation
+// files (the "Software"), to deal in the Software without
+// restriction, including without limitation the rights to use,
+// copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following
+// conditions:
+//
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+// OTHER DEALINGS IN THE SOFTWARE.
+#endregion
+
+#if !NET20
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Runtime.Serialization;
+using System.Text;
+using System.Threading;
+using Newtonsoft.Json.Linq;
+using Newtonsoft.Json.Tests.Documentation.Samples.Serializer;
+using System.Globalization;
+#if DNXCORE50
+using System.Reflection;
+using Xunit;
+using Test = Xunit.FactAttribute;
+using Assert = Newtonsoft.Json.Tests.XUnitAssert;
+#else
+using NUnit.Framework;
+#endif
+
+namespace Newtonsoft.Json.Tests.Issues
+{
+    [TestFixture]
+    public class Issue2768 : TestFixtureBase
+    {
+        [Test]
+        public void Test_Serialize()
+        {
+            decimal d = 0.0m;
+            string json = JsonConvert.SerializeObject(d);
+
+            Assert.AreEqual("0.0", json);
+        }
+
+        [Test]
+        public void Test_Serialize_NoTrailingZero()
+        {
+            decimal d = 0m;
+            string json = JsonConvert.SerializeObject(d);
+
+            Assert.AreEqual("0.0", json);
+        }
+
+        [Test]
+        public void Test_Deserialize()
+        {
+            decimal d = JsonConvert.DeserializeObject<decimal>("0.0");
+
+            Assert.AreEqual("0.0", d.ToString());
+        }
+
+        [Test]
+        public void Test_Deserialize_MultipleTrailingZeroes()
+        {
+            decimal d = JsonConvert.DeserializeObject<decimal>("0.00");
+
+            Assert.AreEqual("0.00", d.ToString());
+        }
+
+        [Test]
+        public void Test_Deserialize_NoTrailingZero()
+        {
+            decimal d = JsonConvert.DeserializeObject<decimal>("0");
+
+            Assert.AreEqual("0", d.ToString());
+        }
+
+        [Test]
+        public void ParseJsonDecimal()
+        {
+            var json = @"{ ""property"": 0.0 }";
+
+            var reader = new JsonTextReader(new StringReader(json))
+            {
+                FloatParseHandling = FloatParseHandling.Decimal
+            };
+
+            decimal? parsedDecimal = null;
+            
+            while (reader.Read())
+            {
+                if (reader.TokenType == JsonToken.Float)
+                {
+                    parsedDecimal = (decimal)reader.Value;
+                    break;
+                }
+            }
+
+            Assert.AreEqual("0.0", parsedDecimal.ToString());
+        }
+
+        [Test]
+        public void ParseJsonDecimal_IsBoxedInstanceSame()
+        {
+            var json = @"[ 0.0, 0.0 ]";
+
+            var reader = new JsonTextReader(new StringReader(json))
+            {
+                FloatParseHandling = FloatParseHandling.Decimal
+            };
+
+            List<object> boxedDecimals = new List<object>();
+
+            // Start array
+            Assert.IsTrue(reader.Read());
+
+            Assert.IsTrue(reader.Read());
+            boxedDecimals.Add(reader.Value);
+
+            Assert.IsTrue(reader.Read());
+            boxedDecimals.Add(reader.Value);
+
+            Assert.IsTrue(reader.Read());
+            Assert.IsFalse(reader.Read());
+
+            // Boxed values will match or not depending on whether framework supports.
+#if NET6_0_OR_GREATER
+            Assert.IsTrue(object.ReferenceEquals(boxedDecimals[0], boxedDecimals[1]));
+#else
+            Assert.IsFalse(object.ReferenceEquals(boxedDecimals[0], boxedDecimals[1]));
+#endif
+
+        }
+    }
+}
+#endif

Src/Newtonsoft.Json/Utilities/BoxedPrimitives.cs

@@ -23,6 +23,9 @@
 // OTHER DEALINGS IN THE SOFTWARE.
 #endregion
 
+using System;
+using System.Diagnostics;
+
 namespace Newtonsoft.Json.Utilities
 {
     internal static class BoxedPrimitives
@@ -87,9 +90,42 @@ internal static class BoxedPrimitives
         internal static readonly object Int64_7 = 7L;
         internal static readonly object Int64_8 = 8L;
 
-        internal static object Get(decimal value) => value == decimal.Zero ? DecimalZero : value;
+        internal static object Get(decimal value)
+        {
+            // Decimals can contain trailing zeros. For example 1 vs 1.0. Unfortunatly, Equals doesn't check for trailing zeros.
+            // There isn't a way to find out if a decimal has trailing zeros in older frameworks without calling ToString.
+            // Don't provide a cached boxed decimal value in older frameworks.
+
+#if NET6_0_OR_GREATER
+            // Number of bits scale is shifted by.
+            const int ScaleShift = 16;
+        
+            if (value == decimal.Zero)
+            {
+                Span<int> bits = stackalloc int[4];
+                int written = decimal.GetBits(value, bits);
+                MiscellaneousUtils.Assert(written == 4);
+
+                byte scale = (byte)(bits[3] >> ScaleShift);
+                // Only use cached boxed value if value is zero and there is zero or one trailing zeros.
+                if (scale == 0)
+                {
+                    return DecimalZero;
+                }
+                else if (scale == 1)
+                {
+                    return DecimalZeroWithTrailingZero;
+                }
+            }
+#endif
+
+            return value;
+        }
 
+#if NET6_0_OR_GREATER
         private static readonly object DecimalZero = decimal.Zero;
+        private static readonly object DecimalZeroWithTrailingZero = 0.0m;
+#endif
 
         internal static object Get(double value)
         {