PreferredMethods: select is not an equivalent substitute for find_all

[fj]

Rubocop's presumption with PreferredMethods seems to be that the "undesired method" is equivalent to the more idiomatic "desired method", so we should use that one.

However, that's not accurate in the case of select and find_all. Consider, e.g., the following simple case:

h = {:a => 1, :b => 2}
# => {:a=>1, :b=>2}

h.find_all { true }
# => [[:a, 1], [:b, 2]]     # <---\
                            #     |
                            #  (these are different!)
h.select { true }           #     |
# => {:a=>1, :b=>2}         # <---/

[bbatsov]

@fj Limitation of static analysis... Both methods are actually the same in Enumerable, but some classes like Hash have a custom select and don't make find_all its alias.

[fj]

OK. Seems like there's no real way to address this short of an implementation change in Ruby itself, so should I go ahead and close this?

[bbatsov]

I'll think some more what we can do about this. /cc @jonas054 @yujinakayama

[fj]

👍