firefoxGcInterval: null does not work as documented

[jennifer-shehane]

Current behavior:

It says in our docs, to turn off firefoxGcInterval for both runMode and openMode, I can just set the following: https://on.cypress.io/configuration#firefoxGcInterval

{
  "firefoxGcInterval": null
}

But this throws an error

I don't see any indication of this setting ever having worked (tried back to 4.0.2).

Full stack trace:

TypeError: intervals is null
    createIntervalGetter/<@https://docs.cypress.io/__cypress/runner/cypress_runner.js:157219:22
    install/<@https://docs.cypress.io/__cypress/runner/cypress_runner.js:157242:30
    listener@https://docs.cypress.io/__cypress/runner/cypress_runner.js:150130:19
From previous event:
    extend/events.emitThen@https://docs.cypress.io/__cypress/runner/cypress_runner.js:150132:22
    extend/events.proxyTo/</parent[fn]@https://docs.cypress.io/__cypress/runner/cypress_runner.js:150082:29
    action@https://docs.cypress.io/__cypress/runner/cypress_runner.js:145451:32
    fire@https://docs.cypress.io/__cypress/runner/cypress_runner.js:151440:18
    testBeforeRunAsync/<@https://docs.cypress.io/__cypress/runner/cypress_runner.js:151450:14
From previous event:
    testBeforeRunAsync@https://docs.cypress.io/__cypress/runner/cypress_runner.js:151448:18
    onRunnableRun@https://docs.cypress.io/__cypress/runner/cypress_runner.js:152462:14
    action@https://docs.cypress.io/__cypress/runner/cypress_runner.js:145442:61
    patchRunnableRun/Runnable.prototype.run@https://docs.cypress.io/__cypress/runner/cypress_runner.js:151262:13
    ../driver/node_modules/mocha/lib/runner.js/</Runner.prototype.runTest@https://docs.cypress.io/__cypress/runner/cypress_runner.js:92961:10
    next/<@https://docs.cypress.io/__cypress/runner/cypress_runner.js:93087:12
    next@https://docs.cypress.io/__cypress/runner/cypress_runner.js:92870:14
    next/<@https://docs.cypress.io/__cypress/runner/cypress_runner.js:92880:11
    next@https://docs.cypress.io/__cypress/runner/cypress_runner.js:92782:14
    ../driver/node_modules/mocha/lib/runner.js/</Runner.prototype.hook/<@https://docs.cypress.io/__cypress/runner/cypress_runner.js:92848:9
    timeslice@https://docs.cypress.io/__cypress/runner/cypress_runner.js:86774:27

Looks like a null value is not being handled at all here:

https://github.com/cypress-io/cypress/blob/develop/packages/driver/src/util/firefox_forced_gc.ts#L3:L3

Desired behavior:

Well, the question is - is this a bug in the code or was this just documented wrong. Not sure which requires updating.

Test code to reproduce

cypress.json - open via cypress open or cypress run in Firefox 72.0.2

{
  "firefoxGcInterval": null
}

Versions

4.0.0+

[cypress-bot]

The code for this is done in cypress-io/cypress#6826, but has yet to be released.
We'll update this issue and reference the changelog when it's released.

[cypress-bot]

Released in 4.3.0.

This comment thread has been locked. If you are still experiencing this issue after upgrading to
Cypress v4.3.0, please open a new issue.