Proposal: Let's add a rule not to use interpolated strings in translations

[jkmassel]

Don't use interpolated strings inside of a call to NSLocalizedString. Use String(format: instead.

Examples

// Correct
let year = 2018
let template = NSLocalizedString("© %d Automattic, Inc.", comment: "Copyright Notice")
let str = String(format: template, year)


// Wrong
let year = 2018
let str = NSLocalizedString("© \(year) Automattic, Inc.", comment: "Copyright Notice")

Rationale

Some translators mentioned in the community Slack that they didn't understand what was being asked for. Because of that, I opened wordpress-mobile/WordPress-iOS#10511. Per @rachelmcr – doing translations this way doesn't work, because the escaping \ doesn't make it into the translation, so it's actually impossible to translate strings that use this format.

Enforcing the rule

I've opened a PR suggesting a Danger rule for this that uses Swiftlint: wordpress-mobile/WordPress-iOS#10526. This issue is an accompaniment to that rule.

[jleandroperez]

Thumbs up on this one!!! Thanks for doing this sir!!