[Plugin] Cannot set property of undefined

[jmsansan]

Current behavior:

On cypress startup, it throws "Cannot set property [key] of undefined" error when modifying config from plugin.
This happens when setting a new object property to config on plugins.

Desired behavior:

Cypress startup properly and loads config on plugins.

Test code to reproduce

add code to /plugins/index.js file and start cypress

module.exports = (on, config) => {
  config.test = { foo: 'bar' }; // Fails
  config.test2 = "foobar"; // Pass
  config.test3 = { foo: {bar: "baz"} }; // Fails
  config.test4 = ["foo", "bar", "baz"]; // Pass
  return config;
};

Versions

Cypress: 4.10.0
OS: Manjaro/Arc linux

[jennifer-shehane]

In terms of what 'fail' means here, the pluginsFile throws an error upon opening.

module.exports = (on, config) => {
  config.test = { foo: 'bar' }; // Fails
  return config;
};

module.exports = (on, config) => {
  config.test.foo = 'bar'; // Fails
  return config;
};

module.exports = (on, config) => {
  config.test3 = { foo: { bar: "baz" } }; // Fails
  return config;
};

[cypress-bot]

The code for this is done in cypress-io/cypress#7960, but has yet to be released.
We'll update this issue and reference the changelog when it's released.

[cypress-bot]

Released in 4.11.0.

This comment thread has been locked. If you are still experiencing this issue after upgrading to
Cypress v4.11.0, please open a new issue.