Clean up DuplicatePropertyNameHandling feature

Src/Newtonsoft.Json.Tests/JsonTextReaderTests/ReadAsyncTests.cs

@@ -1770,11 +1770,11 @@ public async Task ThrowOnDuplicateKeysDeserializingAsync()
                 }
             ";
 
-            JsonLoadSettings settings = new JsonLoadSettings { DuplicatePropertyNamesHandling = DuplicatePropertyNamesHandling.Throw };
+            JsonLoadSettings settings = new JsonLoadSettings { DuplicatePropertyNameHandling = DuplicatePropertyNameHandling.Error };
+
             JsonTextReader reader = new JsonTextReader(new StringReader(json));
-            await ExceptionAssert.ThrowsAsync<JsonException>( async () => await JToken.ReadFromAsync(reader, settings));
+            await ExceptionAssert.ThrowsAsync<JsonReaderException>(async () => await JToken.ReadFromAsync(reader, settings));
         }
     }
-
 }
 #endif

Src/Newtonsoft.Json.Tests/JsonTextReaderTests/ReadTests.cs

@@ -1761,12 +1761,11 @@ public void ThrowOnDuplicateKeysDeserializing()
                 }
             ";
 
-            JsonLoadSettings settings = new JsonLoadSettings {DuplicatePropertyNamesHandling = DuplicatePropertyNamesHandling.Throw};
+            JsonLoadSettings settings = new JsonLoadSettings {DuplicatePropertyNameHandling = DuplicatePropertyNameHandling.Error};
 
-            ExceptionAssert.Throws<JsonException>(() => JObject.Parse(json, settings));
+            JsonTextReader reader = new JsonTextReader(new StringReader(json));
             ExceptionAssert.Throws<JsonException>(() =>
             {
-                JsonTextReader reader = new JsonTextReader(new StringReader(json));
                 JToken.ReadFrom(reader, settings);
             });
         }

Src/Newtonsoft.Json.Tests/Linq/JObjectAsyncTests.cs

@@ -162,6 +162,39 @@ await ExceptionAssert.ThrowsAsync<JsonReaderException>(async () =>
                 await JToken.ReadFromAsync(reader);
             }, "Unexpected end of content while loading JObject. Path 'short.error.code', line 6, position 14.");
         }
+
+        [Test]
+        public async Task ParseMultipleProperties_EmptySettingsAsync()
+        {
+            string json = @"{
+        ""Name"": ""Name1"",
+        ""Name"": ""Name2""
+      }";
+
+            JsonTextReader reader = new JsonTextReader(new StringReader(json));
+            JObject o = (JObject)await JToken.ReadFromAsync(reader, new JsonLoadSettings());
+            string value = (string)o["Name"];
+
+            Assert.AreEqual("Name2", value);
+        }
+
+        [Test]
+        public async Task ParseMultipleProperties_IgnoreDuplicateSettingAsync()
+        {
+            string json = @"{
+        ""Name"": ""Name1"",
+        ""Name"": ""Name2""
+      }";
+
+            JsonTextReader reader = new JsonTextReader(new StringReader(json));
+            JObject o = (JObject)await JToken.ReadFromAsync(reader, new JsonLoadSettings
+            {
+                DuplicatePropertyNameHandling = DuplicatePropertyNameHandling.Ignore
+            });
+            string value = (string)o["Name"];
+
+            Assert.AreEqual("Name1", value);
+        }
     }
 }
 

Src/Newtonsoft.Json.Tests/Linq/JObjectTests.cs

@@ -1604,6 +1604,37 @@ public void ParseMultipleProperties()
             Assert.AreEqual("Name2", value);
         }
 
+        [Test]
+        public void ParseMultipleProperties_EmptySettings()
+        {
+            string json = @"{
+        ""Name"": ""Name1"",
+        ""Name"": ""Name2""
+      }";
+
+            JObject o = JObject.Parse(json, new JsonLoadSettings());
+            string value = (string)o["Name"];
+
+            Assert.AreEqual("Name2", value);
+        }
+
+        [Test]
+        public void ParseMultipleProperties_IgnoreDuplicateSetting()
+        {
+            string json = @"{
+        ""Name"": ""Name1"",
+        ""Name"": ""Name2""
+      }";
+
+            JObject o = JObject.Parse(json, new JsonLoadSettings
+            {
+                DuplicatePropertyNameHandling = DuplicatePropertyNameHandling.Ignore
+            });
+            string value = (string)o["Name"];
+
+            Assert.AreEqual("Name1", value);
+        }
+
 #if !(PORTABLE || DNXCORE50 || PORTABLE40) || NETSTANDARD2_0
         [Test]
         public void WriteObjectNullDBNullValue()

Src/Newtonsoft.Json/Linq/DuplicatePropertyNamesHandling.cs → Src/Newtonsoft.Json/Linq/DuplicatePropertyNameHandling.cs

@@ -28,15 +28,19 @@ namespace Newtonsoft.Json.Linq
     /// <summary>
     /// Specifies how duplicate property names are handled when loading JSON.
     /// </summary>
-    public enum DuplicatePropertyNamesHandling
+    public enum DuplicatePropertyNameHandling
     {
         /// <summary>
-        /// Ignore duplicate properties, use only last value (default)
+        /// Replace the existing value when there is a duplicate property. The value of the last property in the JSON object will be used.
         /// </summary>
-        Ignore = 0,
+        Replace = 0,
         /// <summary>
-        /// Throw exception
+        /// Ignore the new value when there is a duplicate property. The value of the first property in the JSON object will be used.
         /// </summary>
-        Throw = 1
+        Ignore = 1,
+        /// <summary>
+        /// Throw a <see cref="JsonReaderException"/> when a duplicate property is encountered.
+        /// </summary>
+        Error = 2
     }
 }

Src/Newtonsoft.Json/Linq/JContainer.Async.cs

@@ -148,25 +148,15 @@ private async Task ReadContentFromAsync(JsonReader reader, JsonLoadSettings sett
                         parent.Add(v);
                         break;
                     case JsonToken.PropertyName:
-                        string propertyName = reader.Value.ToString();
-                        JProperty property = new JProperty(propertyName);
-                        property.SetLineInfo(lineInfo, settings);
-                        JObject parentObject = (JObject)parent;
-                        // handle multiple properties with the same name in JSON
-                        JProperty existingPropertyWithName = parentObject.Property(propertyName);
-                        if (existingPropertyWithName == null)
+                        JProperty property = ReadProperty(reader, settings, lineInfo, parent);
+                        if (property != null)
                         {
-                            parent.Add(property);
+                            parent = property;
                         }
                         else
                         {
-                            if (settings != null && settings.DuplicatePropertyNamesHandling == DuplicatePropertyNamesHandling.Throw)
-                            {
-                                throw JsonException.Create(lineInfo, property.Path, $"Property with the same name ('{propertyName}') already exists");
-                            }
-                            existingPropertyWithName.Replace(property);
+                            await reader.SkipAsync();
                         }
-                        parent = property;
                         break;
                     default:
                         throw new InvalidOperationException("The JsonReader should not be on a token of type {0}.".FormatWith(CultureInfo.InvariantCulture, reader.TokenType));

Src/Newtonsoft.Json/Linq/JContainer.cs

@@ -837,32 +837,56 @@ internal void ReadContentFrom(JsonReader r, JsonLoadSettings settings)
                         parent.Add(v);
                         break;
                     case JsonToken.PropertyName:
-                        string propertyName = r.Value.ToString();
-                        JProperty property = new JProperty(propertyName);
-                        property.SetLineInfo(lineInfo, settings);
-                        JObject parentObject = (JObject)parent;
-                        // handle multiple properties with the same name in JSON
-                        JProperty existingPropertyWithName = parentObject.Property(propertyName);
-                        if (existingPropertyWithName == null)
+                        JProperty property = ReadProperty(r, settings, lineInfo, parent);
+                        if (property != null)
                         {
-                            parent.Add(property);
+                            parent = property;
                         }
                         else
                         {
-                            if (settings != null && settings.DuplicatePropertyNamesHandling == DuplicatePropertyNamesHandling.Throw)
-                            {
-                                throw JsonException.Create(lineInfo, property.Path, $"Property with the same name ('{propertyName}') already exists");
-                            }
-                            existingPropertyWithName.Replace(property);
+                            r.Skip();
                         }
-                        parent = property;
                         break;
                     default:
                         throw new InvalidOperationException("The JsonReader should not be on a token of type {0}.".FormatWith(CultureInfo.InvariantCulture, r.TokenType));
                 }
             } while (r.Read());
         }
 
+        private static JProperty ReadProperty(JsonReader r, JsonLoadSettings settings, IJsonLineInfo lineInfo, JContainer parent)
+        {
+            DuplicatePropertyNameHandling duplicatePropertyNameHandling = settings?.DuplicatePropertyNameHandling ?? DuplicatePropertyNameHandling.Replace;
+
+            JObject parentObject = (JObject)parent;
+            string propertyName = r.Value.ToString();
+            JProperty existingPropertyWithName = parentObject.Property(propertyName);
+            if (existingPropertyWithName != null)
+            {
+                if (duplicatePropertyNameHandling == DuplicatePropertyNameHandling.Ignore)
+                {
+                    return null;
+                }
+                else if (duplicatePropertyNameHandling == DuplicatePropertyNameHandling.Error)
+                {
+                    throw JsonReaderException.Create(r, "Property with the name '{0}' already exists in the current JSON object.".FormatWith(CultureInfo.InvariantCulture, propertyName));
+                }
+            }
+
+            JProperty property = new JProperty(propertyName);
+            property.SetLineInfo(lineInfo, settings);
+            // handle multiple properties with the same name in JSON
+            if (existingPropertyWithName == null)
+            {
+                parent.Add(property);
+            }
+            else
+            {
+                existingPropertyWithName.Replace(property);
+            }
+
+            return property;
+        }
+
         internal int ContentsHashCode()
         {
             int hashCode = 0;

Src/Newtonsoft.Json/Linq/JsonLoadSettings.cs

@@ -9,7 +9,7 @@ public class JsonLoadSettings
     {
         private CommentHandling _commentHandling;
         private LineInfoHandling _lineInfoHandling;
-        private DuplicatePropertyNamesHandling _duplicatePropertyNamesHandling;
+        private DuplicatePropertyNameHandling _duplicatePropertyNameHandling;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="JsonLoadSettings"/> class.
@@ -18,11 +18,12 @@ public JsonLoadSettings()
         {
             _lineInfoHandling = LineInfoHandling.Load;
             _commentHandling = CommentHandling.Ignore;
-            _duplicatePropertyNamesHandling = DuplicatePropertyNamesHandling.Ignore;
+            _duplicatePropertyNameHandling = DuplicatePropertyNameHandling.Replace;
         }
 
         /// <summary>
         /// Gets or sets how JSON comments are handled when loading JSON.
+        /// The default value is <see cref="CommentHandling.Ignore" />.
         /// </summary>
         /// <value>The JSON comment handling.</value>
         public CommentHandling CommentHandling
@@ -41,6 +42,7 @@ public CommentHandling CommentHandling
 
         /// <summary>
         /// Gets or sets how JSON line info is handled when loading JSON.
+        /// The default value is <see cref="LineInfoHandling.Load" />.
         /// </summary>
         /// <value>The JSON line info handling.</value>
         public LineInfoHandling LineInfoHandling
@@ -58,20 +60,21 @@ public LineInfoHandling LineInfoHandling
         }
 
         /// <summary>
-        /// Gets or sets how duplicate property names are handled when loading JSON.
+        /// Gets or sets how duplicate property names in JSON objects are handled when loading JSON.
+        /// The default value is <see cref="DuplicatePropertyNameHandling.Replace" />.
         /// </summary>
-        /// <value>The JSON duplicate property names handling.</value>
-        public DuplicatePropertyNamesHandling DuplicatePropertyNamesHandling
+        /// <value>The JSON duplicate property name handling.</value>
+        public DuplicatePropertyNameHandling DuplicatePropertyNameHandling
         {
-            get => this._duplicatePropertyNamesHandling;
+            get => _duplicatePropertyNameHandling;
             set
             {
-                if (value< DuplicatePropertyNamesHandling.Ignore|| value> DuplicatePropertyNamesHandling.Throw)
+                if (value < DuplicatePropertyNameHandling.Ignore || value > DuplicatePropertyNameHandling.Error)
                 {
                     throw new ArgumentOutOfRangeException(nameof(value));
                 }
 
-                this._duplicatePropertyNamesHandling = value;
+                _duplicatePropertyNameHandling = value;
             }
         }
     }

Src/Newtonsoft.Json/Newtonsoft.Json.csproj

@@ -34,7 +34,7 @@
     <None Include="..\..\LICENSE.md" Pack="true" PackagePath="LICENSE.md" />
   </ItemGroup>
   <ItemGroup> 
-    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0-beta-62925-02" PrivateAssets="All" />
+    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0-beta-63127-02" PrivateAssets="All" />
   </ItemGroup> 
   <PropertyGroup Condition="'$(TargetFramework)'=='net45'">
     <AssemblyTitle>Json.NET</AssemblyTitle>

Src/global.json

@@ -1,5 +1,4 @@
 {
-  "projects": [ "src" ],
   "sdk": {
     "version": "2.1.500"
   }