Can the runtime dependency on types be moved to devDependencies

[lilwilsond2]

What version of OpenTelemetry are you using?

1.6.0

What version of Node are you using?

18.17.0

What did you do?

The inclusion of @types/express as a runtime dependency causes some typing issues for us in mocked tests.
I found this discussion about why the types were moved originally, but i was wondering if the types could be moved back at this point

What did you expect to see?

type defs as a dev dependency

What did you see instead?

type defs as a runtime dependency

Additional context

fwiw, i added this to my package json and things still seem okay

"resolutions": {
    "@types/express": "link:./node_modules/.cache/null"
  },

[Flarna]

The problem is that ExpressInstrumentation has types from express in it's public interface.
e.g. the requestHook uses type Request.

If some typescript user installs the instrumentation (maybe indirect via autoinstrumentations meta package) but not the express types typescript complains.

Therefore to move it into dev-deps it's additionally needed to cleanup the public API surface as described here.

[david-luna]

@Flarna

The description of requestHook says

Function for adding custom attributes on Express request.

Could we limit the request type to a subset of props (the ones necessary to add attributes) and allowing the user to pass the full type if needed?

export interface SimpleExpressRequest {
  // some props here
}

export type ExpressRequestInfo<T = SimpleExpressRequest> = {
  request: T;
  route: string;
  layerType: ExpressLayerType;
};

[Flarna]

As long as the dependency to express is broken it should be fine. The instrumentation itself doesn't need the hooks therefore I think no need for a SimpleExpressRequest types. We could default to unknown or any.

But for sure the docs need to mention what is actually given to the hook.

[david-luna]

@Flarna @pichlermarc I can prepare a PR. you can assign it to me