Use default value with null inputs

[gregoirechauvet]

On a boolean input field that has a default value, a GraphQL client can send:

• Omit the field (i.e. undefined in JavaScript)
• null
• A boolean

The default value will only be used in the undefined case. Whereas in the null case, null is actually what is received in the resolver.
From my understanding, it's the expected behavior from the GraphQL specification. null is considered a value.
(even though it's quite inconvenient in my opinion 😛)

I would like to always have a boolean here, in all cases. My example here is with a boolean, but it works on all input types.

How the input is declared:

@InputType()
class MyInput {
  @Field({ defaultValue: false })
  myProperty: boolean;
}

One solution is to fix the type and add | null, and handle this case in the resolver. But it's quite cumbersome.

@InputType()
class MyInput {
  @Field({ defaultValue: false })
--  myProperty: boolean;
++  myProperty: boolean | null;
}

I'm looking for a simpler solution. I tried to use the @UseMiddleware() decorator, but it seems they are not working on inputs, only on @ObjectType. Then I tried to wrap the @Field decorator, but I'm not able to patch the values either.

Would you have a solution, or a lead to investigate? What would be the best way to do it?

---

I think the TypeGraphQL documentation is not very clear on this topic. There are no hints, not even with the type system that null can be received, while it's a valid input.

[MichalLytek]

I think your issue has been solved in #806, so when you provide default value, it will no more emit the field as nullable, so null value won't be allowed.

[gregoirechauvet]

Hum... but what's the point of a default value if the field is non-nullable? 🤔
As far as I know, nullable means the field can be omitted, or null can be sent, right? Otherwise, the client is required to send a value. Am I missing something?

[MichalLytek]

Read the discussion in the original issue, everything about default value and null is described there.

[gregoirechauvet]

I did but I'm still confused. But I can try the change and play with it myself.
I'll try with the version from master has the change hasn't been released yet. Thanks for your answers!

[gregoirechauvet]

It works perfectly fine, my understanding of the GraphQL specification wasn't correct. Awesome!
Any new release planned then? 😇

[MichalLytek]

Yes, I need to finish a few things and then v1.2 will be ready!