[release/10.0-preview6] JSON: Don't mark unmapped properties as read

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Object/ObjectWithParameterizedConstructorConverter.cs

@@ -628,8 +628,8 @@ protected static bool TryLookupConstructorParameter(
                 out bool useExtensionProperty,
                 createExtensionProperty: false);
 
-            // Mark the property as read from the payload if required.
-            if (!useExtensionProperty)
+            // Mark the property as read from the payload if it is mapped to a non-extension member.
+            if (!useExtensionProperty && jsonPropertyInfo != JsonPropertyInfo.s_missingProperty)
             {
                 state.Current.MarkPropertyAsRead(jsonPropertyInfo);
             }

src/libraries/System.Text.Json/tests/Common/ConstructorTests/ConstructorTests.ParameterMatching.cs

@@ -1611,7 +1611,7 @@ public async Task TestClassWithManyDefaultParams()
             Class_With_Parameters_Default_Values result = await Serializer.DeserializeWrapper<Class_With_Parameters_Default_Values>(json);
             result.Verify();
         }
-        
+
         [Fact]
         public async Task TestClassWithCustomConverterOnCtorParameter_ShouldPassCorrectTypeToConvertParameter()
         {
@@ -1821,5 +1821,25 @@ public record class Class_ManyParameters_ExtraProperty_ExtData(int P0, int P1, i
             [JsonExtensionData]
             public Dictionary<string, object> ExtensionData { get; set; }
         }
+
+        [Fact]
+        public async Task RequiredMemberWithUnmappedMember()
+        {
+            // https://github.com/dotnet/runtime/issues/116801
+            string json = """
+                {
+                    "Bar": "asdf",
+                    "Baz": "hello"
+                }
+                """;
+
+            ClassWithRequiredProperty obj = await Serializer.DeserializeWrapper<ClassWithRequiredProperty>(json);
+            Assert.Equal("asdf", obj.Bar);
+        }
+
+        public class ClassWithRequiredProperty
+        {
+            public required string? Bar { get; set; }
+        }
     }
 }

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/Serialization/ConstructorTests.cs

@@ -158,6 +158,7 @@ protected ConstructorTests_Metadata(JsonSerializerWrapper stringWrapper)
         [JsonSerializable(typeof(Class_ExtraProperty_ExtData))]
         [JsonSerializable(typeof(Class_ExtraProperty_JsonElementDictionaryExtData))]
         [JsonSerializable(typeof(Class_ManyParameters_ExtraProperty_ExtData))]
+        [JsonSerializable(typeof(ClassWithRequiredProperty))]
         internal sealed partial class ConstructorTestsContext_Metadata : JsonSerializerContext
         {
         }
@@ -311,6 +312,7 @@ public ConstructorTests_Default(JsonSerializerWrapper jsonSerializer) : base(jso
         [JsonSerializable(typeof(Class_ExtraProperty_ExtData))]
         [JsonSerializable(typeof(Class_ExtraProperty_JsonElementDictionaryExtData))]
         [JsonSerializable(typeof(Class_ManyParameters_ExtraProperty_ExtData))]
+        [JsonSerializable(typeof(ClassWithRequiredProperty))]
         internal sealed partial class ConstructorTestsContext_Default : JsonSerializerContext
         {
         }