Addded TrailingCommaRule

[marcelofabri]

Fixes #883.

How would be the best way to handle both styles (mandatory comma and forbidden comma)? A configuration (if so, how should the rule description be)? Another rule?

I made this rule opt-in as even SwiftLint codebase isn't consistent. Thoughts?

PS: The changelog entry is missing on purpose as I thought it'd be better to think on how to handle both styles first.

[codecov-io]

Current coverage is 86.11% (diff: 89.79%)

Merging #886 into master will increase coverage by 0.08%

@@             master       #886   diff @@
==========================================
  Files           112        114     +2   
  Lines          4959       5055    +96   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits           4266       4353    +87   
- Misses          693        702     +9   
  Partials          0          0          

Powered by Codecov. Last update ad019af...50ec4e3

[jpsim]

I think this rule can be on-by-default as long as it's also configurable.

[marcelofabri]

But how would I handle the configurations in the examples? They're very different according to the specified configuration.

[jpsim]

But how would I handle the configurations in the examples? They're very different according to the specified configuration.

True, but that wouldn't be unprecedented. We have other rules where we reuse the convenient RuleDescription examples for tests with the default configuration, but have more explicit tests for custom configurations. For example, see RulesTests.testColon() where we first run the standard verifyRule(ColonRule.description) test, followed by passing in a custom RuleDescription and configuration: verifyRule(description, ruleConfiguration: ["flexible_right_spacing": true]).

Could do the same here, although there's an argument to be made that we should have a nicer way to specify different test examples for each configuration to test.

[marcelofabri]

@jpsim Another (small) problem with the current description behavior is that swiftlint rules [rule] would always show the examples for the default configuration, but it could be interesting to show for the provided one instead. However I do feel that this feature is mostly unused and few people are aware of it.

[jpsim]

Looks great! I've given you write access, since you've done nothing but great contributions! So merge this whenever you feel it's ready.

[jpsim]

just two trailing spaces: https://github.com/realm/SwiftLint/blob/master/CONTRIBUTING.md#tracking-changes

[jpsim]

link to the issue this resolves, not the PR adding it: https://github.com/realm/SwiftLint/blob/master/CONTRIBUTING.md#tracking-changes

[marcelofabri]