New Feature: Forward unknown command line arguments to jest.config.js

🚀 Feature Proposal

Forward unknown command line arguments to jest.config.js file. Right now, jest will respond with "unknown argument’. The proposal is to instead allow these unrecognized arguments so they can be used in the jest.config.js file to modify the config.

Tor-051496:my-project ben$ yarn jest --unit
yarn run v1.5.1
$ /Users/ben/Projects/my-project/node_modules/.bin/jest --unit
● Unrecognized CLI Parameter:

  Unrecognized option "unit".

  CLI Options Documentation:
  https://facebook.github.io/jest/docs/en/cli.html

Motivation

Sometimes you want to slightly change the jest config based on some variable. For example, I might want to only run my unit tests or integration tests instead of all my tests. Or I might want to only test a certain project in a monorepo.

Example

Your cli command would look like this: jest --integration

And you config might look like this:

const argv = require('yargs').argv;
function getTestRegex() {
  if(argv.integration) {
    return `__tests__/integration/\.(ts|js)x?$`;
  }

  return 'test\.(ts|js)x?$';
}

module.exports = {
  "testRegex": getTestRegex(),
}

Alternatives

Alternatively, you could also somehow specify this is a custom flag. The advantage here is that you can keep the “unknown flag” check. The disadvantage is that it becomes a little more verbose.

jest --known-jest-flag --custom-flags --integration or maybe jest --known-jest-flag -f --integration

Right now, you can also use environment variables, but they’re more verbose. TEST_TYPE=integration jest

Pitch

This involves a direct change to the jest cli, and there’s no way to do this outside the core as far as I know.

[thymikee]

Disabling unknown CLI commands was a conscious decision, to align Jest with a lot of UNIX tools, and we’re not going back. We believe this makes sense.

As you already mentioned, this is possible using env variables and I don’t see it being more verbose than a CLI flag. I can’t see any added value by this proposal, but even more config options to maintain.

Sorry to be a bearer of bad news, but I’m going to close this. Thanks for taking the time to prepare a nice feature request, appreciated! Looking forward to more proposals or bug fixes 😃

[thernstig]

Imagine you are using jest-puppeteer to run e2e tests. You might want to supply options like headless=false and slowmo=250, or even other start-up options for Puppeteer.

If a preset like jest-puppeteer could add it’s own commands directly to the Jest CLI, would that not be good? It makes sense to me at least, as long as they are namespaced and validated by the preset.