Allow jest-validate to print deprecation warnings for CLI flags

[SimenB]

Do you want to request a feature or report a bug?
Feature

What is the current behavior?
When jest-validate was created in #2524, it came with support for printing deprecation warnings in configuration.

If the current behavior is a bug, please provide the steps to reproduce and
either a repl.it demo through https://repl.it/languages/jest or a minimal
repository on GitHub that we can yarn install and yarn test.
N/A

What is the expected behavior?
It would be great if we could also print deprecation warnings for CLI flags in the same way. Currently unknown flags throws (which makes sense to catch typos), but it would be great to alert users of removed (or altered) options in a semver-compliant way.

Please provide your exact Jest configuration and mention your Jest, node,
yarn/npm version and operating system.
Jest@master

[Aftabnack]

Is this taken? Can I work on this?

[thymikee]

@Aftabnack not taken :)

[Aftabnack]

It's mine then. 😉

[Aftabnack]

https://github.com/facebook/jest/blob/55c342af240a8aa1acb487a253a6ade4a8a4f4a1/packages/jest-cli/src/cli/args.js#L306-L312

• I am planning to add two more attributes to this here, called isDeprecated (boolean) & deprecationMessage (string)
• I will have a generic template which will print all the deprecation warnings. Avoids the need to have a jest-config/src/deprecated.js with functions to warn on specific attributes.

And also, I am assuming that the above file contains the master list of all the options that can be configured.

/cc @SimenB @thymikee
Thoughts?

[SimenB]

I think that makes sense! 🙂 @thymikee knows this part of the code better than me, though

[Aftabnack]

Also, we don't merge CLI flags with the config.js options. Is this intended? If we don't merge, then deprecation warnings may end up twice. Is this OK?

IMO, we should have CLI flags override it's values specified in the config.

[SimenB]

I agree. Separate issue, though

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