Remove memoization in Config#for_all_cops

[volmer]

Sometimes a Config instance has its internal hash mutated, and changes on AllCops don't get reflected in #for_all_cops due to its memoization.

This problem doesn't happen when AllCops is set initially, but when AllCops is set afterwards @for_all_cops already got instantiated with an empty hash.

This issue is noticeable in ConfigLoaderResolver#resolve_inheritance, which mutates the config to merge the values coming from the parent configuration. When the parent config defines AllCops the values don't get used in places that rely on #for_all_cops.

I checked the git history and I didn't find any reason to have had that method memoized. I also run this change in a fairly large codebase and I didn't notice any noticeable performance decrease.

[etiennebarrie]

It can be reproduced quite easily:

$ mkdir rubocop-3726
$ cd rubocop-3726
$ cat <<EOS >.rubocop-disabled.yml
AllCops:
  DisabledByDefault: true
EOS
$ echo inherit_from: .rubocop-disabled.yml > .rubocop.yml
$ echo self.puts 42 > offense.rb
$ rubocop
Inspecting 1 file
C

Offenses:

offense.rb:1:1: C: Redundant self detected.
self.puts 42
^^^^^^^^^^^^

1 file inspected, 1 offense detected

It worked up to 0.42.0, started failing at 0.43.0:

$ rubocop _0.42.0_
Inspecting 1 file
.

1 file inspected, no offenses detected
$ rubocop _0.43.0_
Inspecting 1 file
C

Offenses:

offense.rb:1:1: C: Redundant self detected.
self.puts 42
^^^^^^^^^^^^

1 file inspected, 1 offense detected

[volmer]

@jonas054 @bbatsov any inputs on this? Maybe a different approach?

[jonas054]

The problem seems to be fixed in 0.46.0 by #3713. Can you confirm?

[volmer]

It is indeed! Thank you.