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

1. 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.

2. [Strict mode] 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   

3. [Strict mode] 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

If you do not have webpack and babel installed, add them like so per the webpack documentation:

npm i babel-loader @babel/core @babel/preset-env webpack -D

After that, we need to add this plugin as a babel plugin for Cypress.

Put this into your plugin/index.js if you have Cypress < 10 version:

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

module.exports = (on) => {
    const options = webpackPreprocessor.defaultOptions
    options.webpackOptions.module.rules[0].use[0].options.plugins = [[thenify, { total_thenify: 'true' }]] // The 'Total' mode is enabled
    on('file:preprocessor', webpackPreprocessor(options))
}

Or put this into your setupNodeEvents within the configuration file if you have Cypress >= 10 version:

        setupNodeEvents(on, config) {
            const thenify = require("cypress-thenify")
            const webpackPreprocessor = require('@cypress/webpack-preprocessor')
            const options = webpackPreprocessor.defaultOptions
            options.webpackOptions.module.rules[0].use[0].options.plugins = [[thenify, { total_thenify: 'true' }]] // The 'Total' mode is enabled
            on('file:preprocessor', webpackPreprocessor(options))
        },

Plugin options

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

  options.webpackOptions.module.rules[0].use[0].options.plugins = [[thenify, { thenify_function_name: 'cyEval'}]] 

Project status notice

This project is in alpha stage. Some bugs are highly likely to be found. Please report any issues or suggestions into the tracker

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