Should a field's type specify null when setting nullable: true?

[mmcgahan]

e.g. from the type-graphql docs:

  @Field({ nullable: true })
  averageRating?: number;

would it be more accurate/type-safe to include null in the field's type, i.e.

  @Field({ nullable: true })
  averageRating?: number | null;

I'm new to type-graphql but I think TS would be able to enforce better safety if the field type included null? If it doesn't matter, is there a simple explanation of why the GQL-related nullable: true is sufficient?

[MichalLytek]

Technically it should be number | null but thanks to the truthy/falsy mechanism in JS, people mostly do:

if (foo) {
  bar();
}

So for TS it makes no difference it it's only undefined or undefined | null.

Moreover, declaring field as T | null forces you to use @Field(() => T) which might be less convinent.

[gregoirechauvet]

I think it's not that reliable to do if (foo). When foo is a boolean, you can't do this otherwise the false case will be handled as undefined and null. Same with number actually, 0 is falsy.
Especially, on nullable inputs, the client can omit the field (i.e. undefined), send null, or send a value. And to handle this we need to check both for undefined and null.

To help with this, is there a way to automatically convert null to undefined? Would that be a good idea? Or with a custom decorator maybe?

[MichalLytek]

you can do if (foo != null) which is checking for both null and undefined.

[gregoirechauvet]

That's true 👍
However, I still need to add | null to all the fields as @mmcgahan suggests, so I can make sure I handle all the cases properly.