Feathers: V3: Types error

[bitflower]

Expected behavior

Doesn't throw typescript error.

Actual behavior

I get this error after updating the types. I did a re-generate of the whole app.

System configuration

Module versions (especially the part that's not working):

"@feathersjs/feathers": "^3.3.1",
"@types/feathersjs__feathers": "^3.1.5",

NodeJS version: 10.15

[bitflower]

CC @j2L4e @TimMensch any ideas ?

[TimMensch]

OK, you have two choices when you're creating your app:

interface ServiceTypes {
    // I'm not actually sure what type this is intended to be, but boolean works.
    authentication: boolean; 
}

const app = express(feathers<ServiceTypes>());
app.service("authentication").hooks({}); // works for me

Or

const app = express(feathers()); // default constructor
app.service("authentication").hooks({}); // also works for me

If you create a ServiceTypes object and pass it as the type of the Feathers app, and then you try to reference a service() that isn't a member of ServiceTypes, app.service() will return never, because that's a type error.

I didn't design this, but it's an elegant bit of type declaration.

[bitflower]

Hi Tim,

thanks for the quick reply!

I wasn't sure where to put the interface ServiceTypes? In which file and folder?

However adding authentication: true to my type export type App = Application.. in app.interface.ts made it work. Is that fine?

It's a generator generated typescript project.

[bitflower]

Do you think this is related to this other issue I have?

https://github.com/DefinitelyTyped/DefinitelyTyped/commit/6c2ae3b20aeb588105b32dee1754dc20f42e2c22#commitcomment-33891529

[deskoh]

See PR https://github.com/feathersjs/feathers/pull/1364 for more details. Essentially, to take advantage of TypeScript checking for mis-spelled services, one could define 'allowed' service names as follows:

type Message = { text: string };
export type Application<{
  'messages': Message,
  //... other services
}>;

Service names that are not defined will result in the mentioned error. Alternatively, one could provide the typings as:

// All service names allowed, but will be typed as `Service<any>`.
export type Application;

// Explicitly allow any other service names, downside is that any mis-spelled service name won't be caught
export type Application<{
  'messages': Message,
  [name: string]: any,
}>;

Note in Feathers Crow (v4) app should be typed as follows (see https://github.com/feathersjs/feathers/issues/1369 for details):

export type Application<{
  'messages': Service<Message>,
}>;

[omidkrad]

I think the Feathers team should consider converting the project to TypeScript. Feathers is a great framework but could come short in type safety because type definitions are maintained separate from the source code and so are not always in sync or complete. Have a look at frameworks like NestJS that are written in TypeScript and getting a great start. Also, I suggest avoiding default exports for several reasons (see 1, 2, 3).

[daffl]

I'm going to close this since v4 comes with TypeScript definitions built in and supported in the CLI and docs. See the migration guide for how to upgrade