support private constructor, members

[messagepack-csharp]

support private constructor, members

[neuecc]

Utf8Json supports this feature, I found how to implements completely smart and keep performance way.
But MessagePack-Csharp needs a little refactoring.
Anyway, I know what to do, so I will finish it.

[qstarin]

I'm experiencing the same behavior as tylerhartwig with MessagePack v1.7.3.4.

[MessagePackObject]
public class Image
{
    [SerializationConstructor] 
    private Image() { }
    
    public Image(params string[] relativePathSegments)
    {
        if (ImagePathProvider.TryGetPaths(relativePathSegments, out var lp, out var ru)) {
            Path = lp;
            Url = ru;
        }
    }

    [Key(0)] public string Path { get; private set; }
    [Key(1)] public string Url { get; private set; }
    [IgnoreMember] public bool Exists => Path != null;
}

MessagePackSerializer.Serialize(value, MessagePack.Resolvers.StandardResolverAllowPrivate.Instance); fails with MessagePack.Internal.MessagePackDynamicObjectResolverException : can't find matched constructor.

If I make the constructor public, it works fine.

[neuecc]

What kind of effect is expected, serializer can not deserialize that have only private constructors.
Of course you can not set it to static private property.

If necessary, please make custom serializer.

public class RecoveryCompletedFormatter : IMessagePackFormatter<RecoveryCompleted>
{
    public int Serialize(ref byte[] bytes, int offset, RecoveryCompleted value, IFormatterResolver formatterResolver)
    {
        // TODO:as you like
    }

    public RecoveryCompleted Deserialize(byte[] bytes, int offset, IFormatterResolver formatterResolver, out int readSize)
    {
        // force create object...
        var uninitializedObject = System.Runtime.Serialization.FormatterServices.GetUninitializedObject(typeof(RecoveryCompletedFormatter));

        // set from bytes...

        // Of course can not set, but use reflection, can set...
        // RecoveryCompleted.Instance = uninitializedObject;

    }
}

This can not be generalized.

[alexvaluyskiy]

JSON.NET supports a private constructor via ConstructorHandling.AllowNonPublicDefaultConstructor. Wire also supports it

[neuecc]

Is it OK to understand that Singleton is irrelevant?

[alexvaluyskiy]

Yes, singleton was an inappropriate example. It is all about private constructor

[neuecc]

Okay.
I know how to handle private constructors and private members as fast.
I'll implement it.

[alexvaluyskiy]

It does not support internal members too

[israellot]

I think using private setters for properties is a good start.

[megakid]

Any progress on this? This is a blocker for us using this superb library.

[megakid]

Awesome work - Really nice job on the UTF8Json library as well.

[neuecc]

I've release v1.7.0, it includes this feature.
you can use new resolvers, StandardResolverAllowPrivate or ContractlessStandardResolverAllowPrivate.

[megakid]

Nice work. Thanks

[tylerhartwig]

Hi, I'm trying to use this library to deal with private constructors.

I have made the following unit test:

    public class UnitTest1
    {
        public T SerializeDeserialize<T>(T obj)
        {
            var serialized = MessagePackSerializer.Serialize(obj, ContractlessStandardResolverAllowPrivate.Instance);
            var unserialized =
                MessagePackSerializer.Deserialize<T>(serialized, ContractlessStandardResolverAllowPrivate.Instance);
            
            return unserialized;
        }

        public class TestType
        {
            public static TestType Create(int initial)
            {
                var t = new TestType();
                t.Val = initial;
                return t;
            }
            
            private TestType() { }
            private int val;

            public int Val
            {
                get { return val; }
                private set { val = value; }
            }
        }

        [Fact]
        public void TestPrivateTestType()
        {
            var testType = TestType.Create(42);

            var actual = SerializeDeserialize(testType);
            Assert.Equal(testType.Val, actual.Val);
        }
    }

This test fails with MessagePack.Internal.MessagePackDynamicObjectResolverException : can't find public constructor.

I'm using MessagePack v1.7.3.4.

Am I using this incorrectly? my understanding from this issue is that the TestType should serializable and deserializable.

[CheeryProgrammer]

SerializationConstructorAttribute does not help :(

[tylerhartwig]

IIRC what I found was that "AllowPrivate" on this MessagePack library only means access to private fields/members, but does not check for private constructors.

Not sure if that helps y'all, but I thought I'd add that in. I ended up making all my constructors public for the time being (though my code base is only myself, so I can enforce my own good practices).