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

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

will be transpiled into this one:

1  cy.get("foo").then(__cypressSyncVar__ => {
2    let a = __cypressSyncVar__;
3    cy.log(a.text());
4    cy.get("bar").then(__cypressSyncVar__ => {
5      let b = __cypressSyncVar__;
6      cy.log(a.text());
7      b.click(); // using jQuery click method
8    });
9  });

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

1    let a = cy.get("foo")
2    cy.log(a.text())
3    let b = cy.get("bar")
4    cy.log(a.text())
5    b.click() // using jQuery click method

will be transpiled into this one:

1cy.get("foo").then(__cypressSyncVar__ => {
2   let a = __cypressSyncVar__;
3   cy.log(a.text());
4   cy.then(() => {
5      cy.get("bar").then(__cypressSyncVar__ => {
6         let b = __cypressSyncVar__;
7         cy.log(a.text());
8         cy.then(() => {
9            b.click(); // using jQuery click method
10         });
11      });
12   });
13});

Limitations

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

1 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:

1   let myValue 
2   if (myCondition) { // suppose myCondition is true
3       myValue = cy.wrap("foo").thenify()
4       someOtherCode()
5       console.log(myValue) // will print 'foo' as we are inside the same block of code as the `thenify` call
6   } else {
7       myValue = "bar"
8   }
9   console.log(myValue) // will print `undefined` as we are out of the initial block of code 
10   cy.thenify()
11   console.log(myValue) // will print 'foo' as we get in sync with the cypress event loop 
12                        // 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

1npm i cypress-thenify -D

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

1npm 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:

1const thenify = require("cypress-thenify")
2const webpackPreprocessor = require('@cypress/webpack-preprocessor')
3
4module.exports = (on) => {
5    const options = webpackPreprocessor.defaultOptions
6    options.webpackOptions.module.rules[0].use[0].options.plugins = [[thenify, { total_thenify: 'true' }]] // The 'Total' mode is enabled
7    on('file:preprocessor', webpackPreprocessor(options))
8}

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

1        setupNodeEvents(on, config) {
2            const thenify = require("cypress-thenify")
3            const webpackPreprocessor = require('@cypress/webpack-preprocessor')
4            const options = webpackPreprocessor.defaultOptions
5            options.webpackOptions.module.rules[0].use[0].options.plugins = [[thenify, { total_thenify: 'true' }]] // The 'Total' mode is enabled
6            on('file:preprocessor', webpackPreprocessor(options))
7        },

Plugin options

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

1  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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