Fix hang when deserializing JTokenReader with preceding comment (#2178)

Src/Newtonsoft.Json.Tests/Issues/Issue1962.cs

@@ -0,0 +1,86 @@
+#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
+
+using System.Linq;
+using Newtonsoft.Json.Linq;
+#if DNXCORE50
+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 Issue1962
+    {
+        [Test]
+        public void Test_Default()
+        {
+            string json = @"// comment
+[ 1, 2, 42 ]";
+            JToken token = JToken.Parse(json);
+
+            Assert.AreEqual(JTokenType.Comment, token.Type);
+            Assert.AreEqual(" comment", ((JValue)token).Value);
+        }
+
+        [Test]
+        public void Test_LoadComments()
+        {
+            string json = @"// comment
+[ 1, 2, 42 ]";
+            JToken token = JToken.Parse(json, new JsonLoadSettings
+            {
+                CommentHandling = CommentHandling.Load
+            });
+
+            Assert.AreEqual(JTokenType.Comment, token.Type);
+            Assert.AreEqual(" comment", ((JValue)token).Value);
+
+            int[] obj = token.ToObject<int[]>();
+            Assert.IsNull(obj);
+        }
+
+        [Test]
+        public void Test_IgnoreComments()
+        {
+            string json = @"// comment
+[ 1, 2, 42 ]";
+            JToken token = JToken.Parse(json, new JsonLoadSettings
+            {
+                CommentHandling = CommentHandling.Ignore
+            });
+
+            Assert.AreEqual(JTokenType.Array, token.Type);
+            Assert.AreEqual(3, token.Count());
+            Assert.AreEqual(1, (int)token[0]);
+            Assert.AreEqual(2, (int)token[1]);
+            Assert.AreEqual(42, (int)token[2]);
+        }
+    }
+}

Src/Newtonsoft.Json/Linq/JTokenReader.cs

@@ -90,6 +90,12 @@ namespace Newtonsoft.Json.Linq
                 }
             }
 
+            // The current value could already be the root value if it is a comment
+            if (_current == _root)
+            {
+                return false;
+            }
+
             _current = _root;
             SetToken(_current);
             return true;