Cannot use cy.readFile or cy.task inside cy.intercept even if promises are supported

[XavierLeTohic]

Current behavior

Using both cy.readFile or cy.task inside cy.intercept will occur the following error:

Desired behavior

We generate fixtures files before running Cypress containing multiple possible responses for each query. We would like to read the generated files in order to match the good mock according to the query's variables but we are unable to use cy.readFile or cy.task (that would use fs) inside cy.intercept.

Test code to reproduce

    cy.intercept('POST', 'http://graphql.test/graphql', (req) => {

      req.alias = operationName;

      const operationName = req.body.operationName;
      const [specName] = Cypress.spec.name.split('.');

      cy.readFile(`mocks/generated/${specName}_${req.body.operationName}.json`, (err, data) => {
        console.log(data)
        console.log(err)
      })
      .then((content) => {
        // we want here to find the good response from `content` according to req.body.variables
        req.reply(content);
      });
    });

Versions

Mac OS 11.2.1
Cypress 6.5.0
Node 14.15.3

[jennifer-shehane]

I can recreate this behavior. I'm not sure what the intended behavior is, but this does seem unexpected.

it('test cy.intercept()', () => {
  cy.intercept('POST', '/users', (req) => {
    cy.readFile('./fixtures/example.json').then((data) => {
      req.reply(data)
    })
  }).as('getUrl')
  cy.visit('https://example.com')
  cy.window().then((win) => {
    const xhr = new win.XMLHttpRequest()
    xhr.open('POST', '/users')
    xhr.send()
  })
  cy.wait('@getUrl')
})

[flotwig]

I think this is a duplicate of #7667 - cy commands are incidentally not supported, but it could use a better error either way