[BUG] TS2339: Property 'on' does not exist on type.

[sebastien-savalle]

Is there an existing issue for this?

• [X] I have searched the existing issues

Current Behavior

We observed a weird behavior when migrating to cds 8 and cds-types 0.7.0.

Custom handler cannot be registered properly. A typescript error is thrown.

error TS2339: Property 'on' does not exist on type 'AdminService'.

import { ApplicationService } from '@sap/cds';

export default class AdminService extends ApplicationService {
  init() {
    this.on('health', () => {
      return { status: 'UP' };
    });
  }
}

But it works when this is cast to ApplicationService.

import { ApplicationService } from '@sap/cds';

export default class AdminService extends ApplicationService {
  init() {
    (this as ApplicationService).on('health', () => {
      return { status: 'UP' };
    });
  }
}

Expected Behavior

No response

References

https://pages.github.tools.sap/cap/docs/tools/cds-typer#typer-top-level-imports

Versions

backend	https://github.com/<your/repo>
@cap-js/asyncapi	1.0.2
@cap-js/audit-logging	0.8.1
@cap-js/cds-types	0.7.0
@cap-js/db-service	1.14.1
@cap-js/hana	1.4.1
@cap-js/openapi	1.0.7
@cap-js/sqlite	1.7.6
@cap-js/telemetry	1.0.1
@sap/cds	8.4.0
@sap/cds-compiler	5.4.0
@sap/cds-dk	8.4.0
@sap/cds-dk (global)	8.4.0
@sap/cds-fiori	1.2.7
@sap/cds-foss	5.0.1
@sap/cds-mtxs	2.3.0
@sap/eslint-plugin-cds	3.0.4
Node.js	v20.15.1

Anything else? Logs?

No response

[sebastien-savalle]

Same code works with cds-types 0.6.5 :(

[daogrady]

Hi Sébastien,

thanks for reporting this issue! This looks a bit like TS is trying to infer the type from the implementation files, which would imply you don't have cds-types installed in your project. Please note that since cds8, @cap-js/cds-types has to be installed explicitly and is no longer pulled in from @sap/cds. Did you add @cap-js/cds-types as devDependency to your project and install it?

Best, Daniel

[daogrady]

Actually, I am pretty sure this is a duplicate of https://github.com/cap-js/cds-types/issues/251

If you do have cds-types installed, can you please run (p)npm rebuild in your project and see, if that fixes the problem?

[sebastien-savalle]

Hi Daniel,

Yes, we do have cds-types installed as you can see in the summary. We use pnpm, so this might be similar to the issue you mentioned.

But, this works well with version 0.6.5.

[daogrady]

Hi Sébastien,

thanks for checking! Please also check out my other suggestion.

Best, Daniel

[hakimio]

pnpm rebuild doesn't fix the issue. Most likely because of the issue with pnpm: https://github.com/cap-js/cds-types/issues/251#issuecomment-2468470167

[daogrady]

Hi Sébastien,

can you please check out @hakimio's suggestion and see if that solves the problem for you? If it does, could you please also elaborate a bit on your setup? Do you use a monorepo? If so, do the submodules of that monorepo have a dependency on cds-types?

Best, Daniel