Add "flatten" attribute to field about async-graphql

[sunli829]

Branch dynamic-interface supports the flatten property, we may need sufficient validation to merge to the master, because this will break the type safety of the interface.

Here are all the tests:

async-graphql/tests/object.rs

Line 4 in 8714185

pub async fn test_object_field_flatten() {

async-graphql/tests/object.rs

Line 41 in 8714185

pub async fn test_simple_object_field_flatten() {

async-graphql/tests/object.rs

Line 73 in 8714185

pub async fn test_object_field_flatten_interface() {

[sunli829]

This is pretty easy to implement, but I can't make an object that contains the flatten fields support Interface.😭

[nicolaiunrein]

Does that mean you cannot support the flatten attribute on interfaces or objects that use flatten cannot implement an interface? I think having flatten would kind of sort #35 in that you can combine a SimpleObject with an Object.

[sunli829]

Yes, it's the same problem. I can't pass data between macros, which makes it impossible. But all of these problems can be solved with generic specialization, so let's wait for this feature to stabilize. 😂

[nicolaiunrein]

So I poked around a little in the code base. I tried to manually (without macros) implement an "Object" by implementing ObjectType, OutputValueType and Type on a struct. I can't quite get create_type_info to work correctly but I thought it should be possible to create a trait Merge with required methods async fn base(&self) -> impl ObjectType and async fn extend(&self) -> impl ObjectType and then implement impl<T> ObjectType for T where T: Merge { ... } so that it registers all fields on the object returned from a call to self.base() and self.extend(). Or maybe even a method like async fn objects(&self) -> Vec<Box<dyn ObjectType>>. Could that work or have I hit a dead end?

[sunli829]

The main reason is that Interface cannot be supported. The field of Interface is function forwarding, which can achieve the purpose of type safety.

[sunli829]

If I don't need to support the Interface, I've actually implemented it.😁

[sunli829]

Unless you abandon the type-safety of the interface, which is not what this library is for.

[sunli829]

The Edge type actually does that, it moves the extra_type to a higher level, but the field inside the extra_type doesn't support interface.

fn Edge::node() and fn Edge::cursor() are actually intended to support the interface.

[nicolaiunrein]

That is very nice! 👍