How best to make the codegen understand a custom directive?

[aprilrd]

Let me start by expressing my gratitude for this set of awesome tools! I was especially blown away by "typescript-react-apollo" with its custom hooks.

Internally, we have a directive called nonNull on FIELD, which makes our gateway treat a nullable field as if it is a non-nullable field. This directive helps the client not to deal with the partial data due to engineering/design complexity.

I'd love to enable the generated types to type a field with this directive as required correctly. But I am not sure where to start for this behavior. Could I get a pointer on where to begin?

For reference, here is the definition of the directive:

directive @nonNull() on FIELD

[dotansimha]

I can recommend you to add a transformation layer that would change the schema according to your needs, based on the spec. So @nonNull can change a field to be non-nullable. This can be done with a custom schema loader: https://graphql-code-generator.com/docs/getting-started/schema-field#custom-schema-loader

[aprilrd]

I appreciate the quick response. But doesn't the schema loader operate at the schema level? The @nonNull directive is at the document level. I am not sure how to use the loader to affect the generated types of documents.

[dotansimha]

Oh, I see now. So I'm not sure that we have a way to support it at the moment. We had a thought to add more lifecycle hooks to the generation process, but it's not there yet.

[aprilrd]

Gotcha. When I looked at the plugin codes, I realized there wasn't a way to extend the functionality of a plugin. So lifecycle methods would be great! Or maybe a "custom document loader" works for my use case.

Regardless, thank you for answering my question.

[jamiter]

@aprilrd, ever found a way to modify the typing based on custom directives?

I'm personally looking for a way to make an @auth directive guarantee there is a userId in the context, where it's optional right now. This would prevent a lot of "if userId is string" checks in resolvers, because the directive guarantees this.

[darkbasic]

@jamiter did you find any way to implement this?

@dotansimha I'm looking for a way to change the context type from IContext to WithRequired<IContext, "user" | "userId"> whenever the accounts.js @auth directive is being used in order to avoid tons of avoidable if (user !== undefined) in the resolvers.

export type WithRequired<T, K extends keyof T> = T & { [P in K]-?: T[P] };

[jamiter]

@darkbasic, I haven't found a solution yet. Maybe @dotansimha can let us know if the required support for this feature has been added. Or send us in the right direction.

If it requires adding or modifying a current plugin, that's fine. If I find the time I could make a stab at it. I just wonder what the best approach would be.

[moetelo]

For people who come across this, see directiveContextTypes field.