cypress-thenify

Rationale

Cypress commands are asynchronous. It's a common pattern to use a then callback to get the value of a cypress command.

However, any callback, especially nested one, makes the code less readable.

This plugin allows wrapping a cypress command call statement into a then callback under the hood and keep your code clean and readable.

Usage example

Strict mode (the default mode):

Given code

    let a = cy.get("foo").thenify()
    cy.log(a.text())
    let b = cy.get("bar").thenify()
    cy.log(a.text())
    b.click() // using jQuery click method

will be transpiled into this one:

  cy.get("foo").then(__cypressSyncVar__ => {
    let a = __cypressSyncVar__;
    cy.log(a.text());
    cy.get("bar").then(__cypressSyncVar__ => {
      let b = __cypressSyncVar__;
      cy.log(a.text());
      b.click(); // using jQuery click method
    });
  });

Total mode:

In this mode, the plugin will thenify all the cy statements. To enable this mode, use total_thenify = 'true' option, see Plugin options section for details. Given code

    let a = cy.get("foo")
    cy.log(a.text())
    let b = cy.get("bar")
    cy.log(a.text())
    b.click() // using jQuery click method

will be transpiled into this one:

cy.get("foo").then(__cypressSyncVar__ => {
   let a = __cypressSyncVar__;
   cy.log(a.text());
   cy.then(() => {
      cy.get("bar").then(__cypressSyncVar__ => {
         let b = __cypressSyncVar__;
         cy.log(a.text());
         cy.then(() => {
            b.click(); // using jQuery click method
         });
      });
   });
});

Limitations (Strict mode)

1. The plugin wraps statements inside the current block of statements only. Use an empty call to cy.thenify() to 'synchronize' the execution context with the cypress event loop:

   let myValue 
   if (myCondition) { // suppose myCondition is true
       myValue = cy.wrap("foo").thenify()
       someOtherCode()
       console.log(myValue) // will print 'foo' as we are inside the same block of code as the `thenify` call
   } else {
       myValue = "bar"
   }
   console.log(myValue) // will print `undefined` as we are out of the initial block of code 
   cy.thenify()
   console.log(myValue) // will print 'foo' as we get in sync with the cypress event loop 
                        // because this and all below statements of the current block will be executed under a `then` callback   

2. Only a single thenify call per statement is currently supported. So

 let a = cy.wrap(1).thenify() + cy.wrap(2).thenify()

will produce an error.

3. The plugin searches for the thenify call only by its name, no deep semantic analysis is performed. So it will transpile any of myObj.thenify() calls. Use the plugin options to define your own unique function name if this default name clashes with any of your existing function (see Plugin options section)

Install and configure

npm i cypress-thenify -D

Put this into your plugin/index.js:

const browserify = require('@cypress/browserify-preprocessor')
const thenify = require("cypress-thenify")

module.exports = (on) => {
  const options = browserify.defaultOptions
  options.browserifyOptions.transform[1][1].plugins.push([thenify, { total_thenify: 'true' }]) // Total mode is enabled 
  on('file:preprocessor', browserify(options))
}

Plugin options

You can define a custom thenify function name by passing options to the plugin:

    options.browserifyOptions.transform[1][1].plugins.push([thenify, { thenify_function_name: 'cyEval' }])

Project status notice

This project is in alpha stage. Some bugs are highly likely to be found.