Cypress.Commands.add type doesn't take into account prevSubject to define the type of the custom command

[IlCallo]

Current behavior

declare global {
  namespace Cypress {
    interface Chainable {
      /**
       * Custom command to select DOM element by data-cy attribute.
       * @example cy.dataCy('greeting')
       */
      dataCy<E extends Node = HTMLElement>(value: string): Chainable<JQuery<E>>;
    }
  }
}

Cypress.Commands.add(
    'dataCy',
    { prevSubject: 'optional' },
    (subject, value) => {
      return cy.get(`[data-cy=${value}]`, {
        withinSubject: subject,
      });
    },
  );

subject and value are inferred as any as prevSubject isn't taken into account and TS expect a single param
If value is removed, the first param becomes string which is wrong
The same problem applies to child commands

Desired behavior

Types should take into consideration prevSubject and use it into a conditional to provide correct typings
There may be other edge cases with element | document | window

Test code to reproduce

https://github.com/cypress-io/cypress/pull/17496/files#diff-facdf706a5238380b5e97c040bc1a5f5cb89e3116f878754dd7fb4e693787715R77

This test is wrong, it should be

Cypress.Commands.add('newCommand', { prevSubject: true }, (subject, arg) => {
    // $ExpectType string
    arg
    return
  })

Cypress Version

9.0.0

Other

No response

[villanuevaSEAT]

We have the same issue 😢

[Nodonisko]

same issue here, problem is both for dual and child custom commands

[radan-iml]

Same here, introduced with this PR, like OP said wrong tests.

[Nodonisko]

Also this test for optional subject should be added:

Cypress.Commands.add('newCommand', { prevSubject: 'optional' }, (subject, arg) => {
    // $ExpectType string
    arg
    return
  })

[keeema]

Same issue:

This was working in Cypress < 9.0.0

declare namespace Cypress {
    interface Chainable<Subject> {
        myCommand(options?: Partial<Cypress.Loggable>): Cypress.Chainable<Window>;
    }
}

Cypress.Commands.add(
    "myCommand",
    {
        prevSubject: ["optional", "window"],
    },
    (prevSubject?: Window, options?: Partial<Cypress.Loggable>): Cypress.Chainable<Window> => {
       ....some code....
    }
);

It is not working in Cypress 9.0.0.
I have looked to given example mentioned in PR.
But cypress-image-snapshot is JS plugin with external d.ts. Not a TS plugin.

[cypress-bot]

The code for this is done in cypress-io/cypress#19003, but has yet to be released.
We'll update this issue and reference the changelog when it's released.

[cypress-bot]

Released in 9.2.0.

This comment thread has been locked. If you are still experiencing this issue after upgrading to
Cypress v9.2.0, please open a new issue.