Argument of type '() => void' is not assignable to parameter of type '() => Chainable<any>'.

Current behavior

With the upgrade to v9, Cypress is reporting the following error when adding a custom method:

Argument of type '() => void' is not assignable to parameter of type '() => Chainable<any>'.

Desired behavior

According to the documentation, no other code should be needed to make this work.

Thus I believe that void should be a valid type to be supported.

Test code to reproduce

Cypress.Commands.add('login', () => {
  // do something
})

Cypress Version

9.0.0

Other

No response

[LuisValgoi]

Same thing here…

[mleblancbpa]

If anybody else falls here to find out how to get rid of typescript error in declaring commands, you have to wrap your declare namespace Cypress bloc in a declare global { ... } block like so:

declare global {
  namespace Cypress {
    interface Chainable {
      login(): void;
    }
  }
}