[Configuration] allow configuring parameterized rules from the configuration file

[jpsim]

This is awkwardly implemented at the moment because we're starting to duplicate the set of rules in quite a few places, but this works for now.

line_length:
  - 120 # Very Low
  - 140 # Low
  - 160 # Medium
  - 180 # High
  - 200 # Very High

Thoughts @segiddins @keith ?

[keith]

Personally I question the need for the different levels of severity. But I also think projects should have 0 warnings. Regardless 5 of them may be a little more than needed?

I also think that if someone only provides a single number for these it should actually correspond to very high, and work backwards to very low. In our project I would just use very high at 110 for line length for example.

[jpsim]

Personally I question the need for the different levels of severity.

Same here, to be honest. The original idea was that you may want to warn for some levels, but fail/error for more severe cases. Or you may want to set a minimum severity level you care about depending on the situation? But I think in practice, that complicates usage of SwiftLint more than helping.

Maybe just moving to 2 severity levels (warning & error, which is all that Xcode can present anyway) would be the best way forward?

I understand your intentions in proposing going backwards in the list of parameters, but I think that could get confusing.

[keith]

I think warning vs error is a good distinction. I get that reversing is confusing, I'm not sure what the best way to handle this when someone just adds a single parameter. That is pretty confusion from the users side.

[keith]

Actually if there are only 2 levels I think it makes a lot of sense to be an error unless you add multiple. With 5 reversing is definitely complicated.

[keith]

Can this be removed now?

[jpsim]

not really, we still need a way to access the parameters.

[jpsim]

This has been rebased off master with the changes from #114 so there are now only two severity levels, warning and error.

[jpsim]

Marking this as work-in-progress until I can refactor this a bit to bundle a config file in the SwiftLintFramework.framework bundle and define the default rule parameters in there rather than in code. Thanks @segiddins for the idea.

This will require the ability to "merge" configuration files (framework bundled file + custom file).

[jpsim]

Turns out that refactoring to bundle a config file in the framework and adding the ability to merge config files is a bit out of scope for this PR, and is holding back a release, so I'll merge this now and create a new GitHub issue to track doing this refactoring in the future.

[keith]

Sounds good!