feat(config): external configuration files

[noomorph]

• This change has been discussed in issue point to a single configuration file #901, Allow giving detox config file as param, with fallbacks #906, feat(local-cli): using cosmiconfig to remove requirement on package.j… #1910, and the solution has been agreed upon with maintainers.

Resolves #901.

Description:

1. Makes both parameters optional in detox.init(config[, userParams]) signature.

a. Renames config to configOverride. Speaking lodash language, we deep-merge: _.merge(configFromFile, configOverride). Also, userParams parameter is redundant, since you can tweak its behavior via the first configOverride parameter, or right in the config file. Below is an example for sake of the demonstration:

await detox.init({
  selectedConfiguration: process.env.platform === 'android' ? 'android.emulator' : 'ios.simulator',
  artifacts: { rootDir: '.artifacts' },
  behavior: {
    init: { exposeGlobals: false, reinstallApp: false, launchApp: false },
    cleanup: { shutdownDevice: true },
  },
});

2. Speaking of the aforementioned configFromFile variable, it represents Detox configuration object, imported either from .detoxrc, .detoxrc.json, .detoxrc.js, detox.config.json, detox.config.js, package.json (detox section) in the current working directory, or from process.env.configPath (--config-path CLI argument) path override. If you are using detox-cli, you will have to specify --config-path path/to/.detoxrc parameter to pass it explicitly to mocha or jest runner.

Acknowledgements:

Thanks to @Debens and @oreporan for their early work on this feature. It took long to implement this feature, though the path we walked wasn't short and easy either - there were many configuration refactors preceding it. 🤔

[coveralls]

Pull Request Test Coverage Report for Build 2170

• 130 of 130 (100.0%) changed or added relevant lines in 13 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.4%) to 77.381%

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Totals
Change from base Build 1193:	0.4%
Covered Lines:	3266
Relevant Lines:	3936

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💛 - Coveralls