Additional control over resolver arguments

[meh]

Description of the feature

I'd like to be able to tell if a resolver argument was passed or explicitly set to null.

Code example (if possible)

async fn update(&self, foo: Parameter<i32>, bar: Parameter<Input>)

Now this Parameter would be equivalent to Option, but for the sake of clarity it's a different enum.

This means that in the case of Parameter<Option<T>> I can discern between a parameter not being passed, a null, and a value.

This might be possible to handle by abusing default but I'm not entirely sure about the semantics in that case, and a Parameter type would make that clearer.

I need this to implement decent partial updates to objects.

[oscartbeaumont]

You should have a look at MaybeUndefined<T>. You can see more information about how it works here.

[meh]

That's exactly what I wanted :panda_face:

[oscartbeaumont]

It also took me a while to find when I ran into the same use case as you have.

@sunli829 Is MaybeUndefined<T> included in the async-graphql book website? Because if it is missing from the website I can do a PR to add a section about it so it is easier to find.

[sunli829]

@oscartbeaumont I am so happy that you can help me add this to the book. 🙂

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