Style/AndOr suggests replacing "and" with "&&", and doesn't autocorrect, in places where "and" and "&&" have different semantics

[dmolesUC]

Consider the following:

@h = { a: {b: 'c'} } 

def find_value_1(k1, k2)
  h1 = @h[k1] and h1[k2]
end

def find_value_2(k1, k2)
  h1 = @h[k1] && h1[k2]
end

find_value_1(:a, :b)
# => "c"

find_value_2(:a, :b)
# NoMethodError: undefined method `[]' for nil:NilClass
#   from (irb):8:in `find_value_2'
#   from (irb):13

Rubocop suggests “Use && instead of and” for methods like find_value_1. (To its credit, it doesn't autocorrect with -a, though.)

I understand that the style guide bans use of and for any purpose, but in that case it seems like Rubocop should suggest a different idiom (and/or warn about parentheses / precedence) here, rather than a substitution that will fail.

[alexdowad]

Did you use --auto-correct to fix the problem? If so, RC should add parentheses as needed, so the meaning of the expression is not changed.

...Though even if not autocorrecting, RC could mention precedence in cases where it makes a difference. We have the technology to do that.

[dmolesUC]

It doesn't autocorrect. Maybe that's the bug?

$ bundle exec rubocop --auto-correct
Inspecting 16 files
...C............

Offenses:

lib/factory/factory/abstract_factory.rb:68:40: C: Use && instead of and.
        products = product_registry[k] and products[v.to_s]
                                       ^^^

16 files inspected, 1 offense detected

[dmolesUC]

As a side note, the failure to autocorrect got me to actually read up on the and/&& difference, so I guess there's a pedagogical benefit.

[alexdowad]

When I cut-and-paste find_value_1 into a new source file and run rubocop -a, it is auto-corrected, and parentheses are added, like this:

# encoding: utf-8
def find_value_1(k1, k2)
  (h1 = @h[k1]) && h1[k2]
end

The second example is corrected to:

# encoding: utf-8
(products = product_registry[k]) && products[v.to_s]

...Maybe there is some surrounding context in lib/factory/factory/abstract_factory.rb which makes a difference? Can you share that file (or a portion of it which can reproduce the problem)?

[bbatsov]

@dmolesUC3 what's your RuboCop version btw?

[jonas054]

I did a little digging. Found that the inspected code must have been and older revision (e.g. 7720451) of https://github.com/dmolesUC3/config-factory

Stripping down the code to a minimal example, I found that there's no auto-correction of

def x
end

def y
  a = b and a.c
end

but if I remove the method x, the expression inside y will be auto-corrected.

[alexdowad]

Awesome detective work @jonas054!

[alexdowad]

Just pushing a fix to my open PR. It turns out this is my bug.

[dmolesUC]

@jonas054 Nice work! Thanks.