Is there any way to know if a type can be serialized by Inspector?

[akeit]

ValueTuples have [Serializable] attributes and Public fields, but they can not be serialized.
Vector3 and some built-in types don’t have [Serializable] attributes, but they can be serialized.
Is there any way to know if a type can be serialized by Inspector from C#?

[Kurt-Dekker]

The Unity docs would be the best place to start your investigation.

Serialization in Unity

[system]

@akeit

if a type can be serialized by Inspector

Unity - Manual: Script serialization

[akeit]

@Kurt-Dekker

The Unity docs would be the best place to start your investigation.

https://blog.unity.com/engine-platform/serialization-in-unity

https://docs.unity3d.com/Manual/script-Serialization.html

I already know them.
ValueTuple is an exception to what they say, and I also want to know how to make certain types fit into Unity built-in types.
Does everything in the UnityEngine namespace apply to inspector serializable?

[system]

@akeit

ValueTuple is an exception to what they say

Why? I think ValueTuple is exactly what they say: it is not serializable because it doesn’t fulfill the rules they laid out on the link I provided above.
What is the exact exception?

@akeit

Does everything in the UnityEngine namespace apply to inspector serializable?

It doesn’t dependent where it is declared, it depends on the rules you can find on the link I provided above.
Especially these, but the rest also apply:

To use field serialization you must ensure that the field:

• Is public, or has a SerializeField attribute

• isn’t static

• isn’t const

• isn’t readonly

• Has a field type that can be serialized:

• Primitive data types (int, float, double, bool, string, etc.)

• Enum types (32 bites or smaller)

• Fixed-size buffers

• Unity built-in types, for example, Vector2, Vector3, Rect, Matrix4x4, Color, AnimationCurve

• Custom structs with the Serializable attribute

• References to objects that derive from UnityEngine.Object

• Custom classes with the Serializable attribute. (See Serialization of custom classes).

• An array of a field type mentioned above

• A List of a field type mentioned above

Note: Unity doesn’t support serialization of multilevel types (multidimensional arrays, jagged arrays, dictionaries, and nested container types). If you want to serialize these, you have two options:

• Wrap the nested type in a class or struct
• Use serialization callbacks, by implementing ISerializationCallbackReceiver, to perform custom serialization.

ValueTuple currently doesn’t fulfill these rules.

@akeit

know how to make certain types fit into Unity built-in types

Wrap in a Serializable class using this:

• Use serialization callbacks, by implementing ISerializationCallbackReceiver, to perform custom serialization.

[akeit]

As an example, this is part of the code for ValueTuple<T1, T2>.

[Serializable]
  [StructLayout(LayoutKind.Auto)]
  public struct ValueTuple<T1, T2> :
    IEquatable<(T1, T2)>,
    IStructuralEquatable,
    IStructuralComparable,
    IComparable,
    IComparable<(T1, T2)>,
    IValueTupleInternal,
    ITuple
  {
    public T1 Item1;
    public T2 Item2;

When I copy and paste this code and remove IValueTupleInternal interface, it can be serialized.

[CodeSmile]

If I’m not mistaken Unity cannot serialize a generic type T with no restrictions (aka “where T: System.Object”). This means it could literally be anything.

It might work with [SerializeReference] though.

[Kurt-Dekker]

@akeit

As an example, this is part of the code for ValueTuple<T1, T2>.

What part of that code changes what has already been noted above?

[system]

@akeit

When I copy and paste this code

Well, of course, custom structs (when fulfill the rules I even pasted for you above) can be serialized. And when you do that, it becomes a custom struct called “ValueTuple” and it won’t be the C# type ValueTuple

But as @Kurt-Dekker asked above, what’s your point?

[akeit]

@Kurt-Dekker

What part of that code changes what has already been noted above?

I can’t find what rule is not fulfilled.
The TupleTest below has been serialized.

public ValueTuple<int, int> TupleTest;
[Serializable]
[StructLayout(LayoutKind.Auto)]
public struct ValueTuple<T1, T2> {
    public T1 Item1;
    public T2 Item2;

    public ValueTuple(T1 item1, T2 item2) {
        this.Item1 = item1;
        this.Item2 = item2;
    }
}

[akeit]

Well, of course, custom structs (when fulfill the rules I even pasted for you above) can be serialized. And when you do that, it becomes a custom struct called “ValueTuple” and it won’t be the C# type ValueTuple

But as @Kurt-Dekker asked above, what’s your point?

I copied from mscorlib.dll.

[system]

@akeit

I copied from mscorlib.dll.

Yeah, that’s only .NetFramework, in .NetStandard (netstandard.dll) it looks like this:

public partial struct ValueTuple<T1, T2> : System.Collections.IStructuralComparable, System.Collections.IStructuralEquatable, System.IComparable, System.IComparable<System.ValueTuple<T1, T2>>, System.IEquatable<System.ValueTuple<T1, T2>>, System.Runtime.CompilerServices.ITuple
{
     public T1 Item1;
     public T2 Item2;

     [...]
}

Unity Serializer probably implements the lowest common denominator here. I’m obviously not sure because I don’t work at Unity.

[akeit]

Ah, I understand, UnityEngine does not seem to look for Serializable types in mscorlib.dll or UnityEngine.dll.