Add explicit error when a section is empty

[bankair]

Raises a ValidationError "empty section #{name} found in #{loaded_path || self}" instead of 'undefined method `each_key' for nil:NilClass' when the configuration file contains an empty section.

closes issue #1782

[bbatsov]

Looks good to me. @jonas054 what do you think?

[bquorning]

It’s not immediately obvious (to me, at least) what loaded_path || self would return. Maybe extract it to a variable with a descriptive name?

[bankair]

Hi,

That expression is used at least 2 other times in that file.

The way I see things, I could factorize it in a method called loaded_path_or_self, but I'm not sure it will add something to the code comprehension.

@bbatsov, what's your input on this ?

[bquorning]

Ah, I didn’t see that the expression was used already. Surely re-using it should be ok for this PR.

[jonas054]

👍 Looks good! I agree that loaded_path || self is a bit weird. It's there to support specs that create a cop without configuration, but all specs still pass if you remove || self. Leave it for now.

[bankair]

Thanks for your feedbacks, guys.

[bbatsov]

Why is / escaped?

[bankair]

My mistake. Thanks for noticing.

[bbatsov]

Please, rebase on top of the current master.

[bankair]

Done.

[bbatsov]

👍

[kWhittington]

Should this fix have worked it's way into v0.32.0? I'm getting the undefined methodeach_key' for false:FalseClass` with this config:

# Please see the following for configuration options:
#   https://github.com/bbatsov/rubocop
#   https://github.com/nevir/rubocop-rspec
require: rubocop-rspec

AllCops:
  RunRailsCops: true

Documentation: false

When I remove the Documentation: false bit, rubocop works again:

# Please see the following for configuration options:
#   https://github.com/bbatsov/rubocop
#   https://github.com/nevir/rubocop-rspec
require: rubocop-rspec

AllCops:
  RunRailsCops: true

Do you think this error is related to the bug this P.R. is fixing?