add new JsonIgnoreAttribute WhenWriting/WhenReading

src/libraries/System.Text.Json/Common/JsonIgnoreCondition.cs

@@ -30,5 +30,13 @@ public enum JsonIgnoreCondition
         /// This is applied only to reference-type properties and fields.
         /// </summary>
         WhenWritingNull = 3,
+        /// <summary>
+        /// Property is ignored during serialization
+        /// </summary>
+        WhenWriting = 4,
+        /// <summary>
+        /// Property is ignored during deserialization
+        /// </summary>
+        WhenReading = 5,
     }
 }

src/libraries/System.Text.Json/ref/System.Text.Json.cs

@@ -1028,6 +1028,8 @@ public enum JsonIgnoreCondition
         Always = 1,
         WhenWritingDefault = 2,
         WhenWritingNull = 3,
+        WhenWriting = 4,
+        WhenReading = 5,
     }
     [System.AttributeUsageAttribute(System.AttributeTargets.Field | System.AttributeTargets.Property, AllowMultiple=false)]
     public sealed partial class JsonIncludeAttribute : System.Text.Json.Serialization.JsonAttribute

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonPropertyInfoOfT.cs

@@ -429,6 +429,14 @@ private protected override void ConfigureIgnoreCondition(JsonIgnoreCondition? ig
                     IgnoreDefaultValuesOnWrite = true;
                     break;
 
+                case JsonIgnoreCondition.WhenWriting:
+                    ShouldSerialize = ShouldSerializeIgnoreConditionAlways;
+                    break;
+
+                case JsonIgnoreCondition.WhenReading:
+                    Set = null;
+                    break;
+
                 default:
                     Debug.Fail($"Unknown value of JsonIgnoreCondition '{ignoreCondition}'");
                     break;

src/libraries/System.Text.Json/tests/Common/PropertyVisibilityTests.cs

@@ -2165,6 +2165,35 @@ public async Task IgnoreConditionWhenWritingDefault_WinsOver_IgnoreReadOnlyField
             Assert.Equal(@"{}", json);
         }
 
+        [Fact]
+        public async Task JsonIgnoreCondition_WhenWriting()
+        {
+            var options = new JsonSerializerOptions { IgnoreReadOnlyProperties = true };
+            var json = await Serializer.SerializeWrapper
+                (
+                    new JsonIgnoreCondition_WhenReadingWritingTestModel { Age = 10, Name = "Mike" },
+                    options
+                );
+            Assert.Equal("""{"Age":10}""", json);
+        }
+
+        [Fact]
+        public async Task JsonIgnoreCondition_WhenReading()
+        {
+            var json = """{"Age":10, "Name":"Mike"}""";
+            var model = await Serializer.DeserializeWrapper<JsonIgnoreCondition_WhenReadingWritingTestModel>(json);
+            Assert.Equal("Mike", model.Name);
+            Assert.Equal(0, model.Age);
+        }
+
+        public class JsonIgnoreCondition_WhenReadingWritingTestModel
+        {
+            [JsonIgnore(Condition = JsonIgnoreCondition.WhenReading)]
+            public int Age { get; set; }
+            [JsonIgnore(Condition = JsonIgnoreCondition.WhenWriting)]
+            public string? Name { get; set; }
+        }
+
         public class ClassWithReadOnlyStringProperty
         {
             public string MyString { get; }

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

@@ -129,7 +129,7 @@ public override async Task HonorJsonPropertyName_PrivateGetter()
             Assert.Equal(MySmallEnum.AnotherValue, obj.GetProxy());
 
             // JsonInclude for private members not supported in source gen
-            await Assert.ThrowsAsync<InvalidOperationException>(async() => await Serializer.SerializeWrapper(obj));
+            await Assert.ThrowsAsync<InvalidOperationException>(async () => await Serializer.SerializeWrapper(obj));
         }
 
         [Fact]
@@ -331,7 +331,8 @@ public override async Task ClassWithIgnoredAndPrivateMembers_DoesNotIncludeIgnor
         [JsonSerializable(typeof(IDiamondInterfaceHierarchyWithNamingConflict.IJoinInterface), TypeInfoPropertyName = "IDiamondInterfaceHierarchyWithNamingConflictIJoinInterface")]
         [JsonSerializable(typeof(IDiamondInterfaceHierarchyWithNamingConflictUsingAttribute.IJoinInterface), TypeInfoPropertyName = "IDiamondInterfaceHierarchyWithNamingConflictUsingAttributeIJoinInterface")]
         [JsonSerializable(typeof(CollectionWithPrivateElementType))]
-        [JsonSerializable(typeof(DictionaryWithPrivateKeyAndValueType))][JsonSerializable(typeof(ClassWithIgnoredAndPrivateMembers))]
+        [JsonSerializable(typeof(DictionaryWithPrivateKeyAndValueType))]
+        [JsonSerializable(typeof(ClassWithIgnoredAndPrivateMembers))]
         [JsonSerializable(typeof(ClassWithInternalJsonIncludeProperties))]
         [JsonSerializable(typeof(ClassWithIgnoredAndPrivateMembers))]
         [JsonSerializable(typeof(ClassUsingIgnoreWhenWritingDefaultAttribute))]
@@ -340,6 +341,7 @@ public override async Task ClassWithIgnoredAndPrivateMembers_DoesNotIncludeIgnor
         [JsonSerializable(typeof(ClassWithProperty_IgnoreConditionAlways_Ctor))]
         [JsonSerializable(typeof(ClassWithClassProperty_IgnoreConditionWhenWritingDefault_Ctor))]
         [JsonSerializable(typeof(StructWithStructProperty_IgnoreConditionWhenWritingDefault_Ctor))]
+        [JsonSerializable(typeof(JsonIgnoreCondition_WhenReadingWritingTestModel))]
         [JsonSerializable(typeof(SmallStructWithValueAndReferenceTypes))]
         [JsonSerializable(typeof(WrapperForClassWithIgnoredUnsupportedDictionary))]
         [JsonSerializable(typeof(Class1))]
@@ -613,6 +615,7 @@ partial class DefaultContextWithGlobalIgnoreSetting : JsonSerializerContext;
         [JsonSerializable(typeof(ClassWithProperty_IgnoreConditionAlways_Ctor))]
         [JsonSerializable(typeof(ClassWithClassProperty_IgnoreConditionWhenWritingDefault_Ctor))]
         [JsonSerializable(typeof(StructWithStructProperty_IgnoreConditionWhenWritingDefault_Ctor))]
+        [JsonSerializable(typeof(JsonIgnoreCondition_WhenReadingWritingTestModel))]
         [JsonSerializable(typeof(SmallStructWithValueAndReferenceTypes))]
         [JsonSerializable(typeof(WrapperForClassWithIgnoredUnsupportedDictionary))]
         [JsonSerializable(typeof(Class1))]

src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/MetadataTests/DefaultJsonTypeInfoResolverTests.JsonPropertyInfo.cs

@@ -908,6 +908,7 @@ public enum ModifyJsonIgnore
         [InlineData(JsonIgnoreCondition.Never, ModifyJsonIgnore.DontModify)]
         [InlineData(JsonIgnoreCondition.WhenWritingDefault, ModifyJsonIgnore.NeverSerialize)]
         [InlineData(JsonIgnoreCondition.WhenWritingNull, ModifyJsonIgnore.NeverSerialize)]
+        [InlineData(JsonIgnoreCondition.WhenWriting, ModifyJsonIgnore.NeverSerialize)]
         [InlineData(JsonIgnoreCondition.Never, ModifyJsonIgnore.NeverSerialize)]
         [InlineData(JsonIgnoreCondition.WhenWritingDefault, ModifyJsonIgnore.AlwaysSerialize)]
         [InlineData(JsonIgnoreCondition.WhenWritingNull, ModifyJsonIgnore.AlwaysSerialize)]