CD
Cloudflare Developers•2mo ago
scook

Workers service binding Typescript types uses Rpc.Stub<null>

Hi team, I cannot get TS return types working as expected when calling a method via service binding between Workers. My goal is to have the service return in the form: 
type ServiceResponseSuccess<T> = {
    data: T;
    error: null;
};
type ServiceResponseFailure = {
    data: null;
    error: MyErrorObject;
};
export type ServiceResponse<T> = ServiceResponseFailure | ServiceResponseSuccess<T>;


// my-service.ts:
async myMethod(...): Promise<ServiceResponse<boolean>>;
type ServiceResponseSuccess<T> = {
    data: T;
    error: null;
};
type ServiceResponseFailure = {
    data: null;
    error: MyErrorObject;
};
export type ServiceResponse<T> = ServiceResponseFailure | ServiceResponseSuccess<T>;


// my-service.ts:
async myMethod(...): Promise<ServiceResponse<boolean>>;
and then the caller can do: 
const { data, error } = await myService.myMethod(...);
const { data, error } = await myService.myMethod(...);
The issue is that the generated TS types for the service use Rpc.Stub<null> instead of raw null. And this does not play nice with anything the caller would want to do afterwards. For example, if (error) does not work to check if we're in the error case, since Rpc.Stub<null> != null; and the same null-check doesn't work for the data object. 
// generated TS return type for the service
Promise<{ data: Rpc.Stub<null>; error: {...}; }> 
| Promise<{ data: {...}; error: Rpc.Stub<null>; }>
// generated TS return type for the service
Promise<{ data: Rpc.Stub<null>; error: {...}; }> 
| Promise<{ data: {...}; error: Rpc.Stub<null>; }>
Btw, it appears to only use Rpc.Stub<> for null and undefined. For all other types (number, boolean, custom types, etc) , the generated TS uses the actual type.
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