Odd inconsistency with --cache-root

[dgollahon]

Expected behavior

Configuring --cache-root would behave exactly like setting RUBOCOP_CACHE_ROOT or AllCops: CacheRootDirectory, modulo precedence.

Actual behavior

The --cache-root flag specifies the exact cache folder. The other two options end up creating a nested rubocop_cache directory. I think I see from the code why this is happening but it is perplexing as an end user (and messed up my CI cache at first).

Steps to reproduce the problem

Specify a directory to --cache-root and separately either of the other options and observe that the directory structure it creates is different.

RuboCop version

1.31.0 (using Parser 3.1.2.0, rubocop-ast 1.18.0, running on ruby 2.7.6 x86_64-linux)
  - rubocop-performance 1.14.2
  - rubocop-rspec 2.11.1

I'm not sure if this should be changed to match or if the difference should just be documented but it is very surprising as-is. I actually prefer the --cache-root behavior (so i don't have an extra nesting of directories) but the main issue here is that it is confusing.

[jonas054]

I think this is a bug. A rubocop_cache directory level should be added, also for --cache_root.