Style/For should be marked as unsafe

[diesl]

Cop Style/For should be marked as unsafe, because it can break code

Reason might be that scopes are different, as quoted from Ruby Style Guide

for doesn’t introduce a new scope (unlike each) and variables defined in its block will be visible outside it.

---

Expected behavior

I expect safe autocorrection not to break my existing ruby code.

Actual behavior

Running a cop marked as safe breaks my existing ruby code.

Steps to reproduce the problem

for n in 1..3 do
  x = "numbers:" if n == 1
  x = x + " " + n.to_s
  puts x
end

# output is
# numbers: 1
# numbers: 1 2
# numbers: 1 2 3

When I run rubocop -a --only Style/IdenticalConditionalBranches, it autocorrects my file to:

(1..3).each do |n|
   x = "numbers:" if n == 1
   x = x + " " + n.to_s
  puts x
end

# output is
# numbers: 1
# NoMethodError (undefined method `+' for nil:NilClass)

RuboCop version

$ [bundle exec] rubocop -V
1.25.1 (using Parser 3.1.0.0, rubocop-ast 1.15.2, running on ruby 2.7.5 x86_64-linux)
  - rubocop-performance 1.13.2
  - rubocop-rails 2.13.2
  - rubocop-rspec 2.8.0

[jonas054]

I think you mean rubocop -a --only Style/For, but you're right about the reason for the failure. It's the change in scope for the x variable in this case.

I agree. Marking it as unsafe is a simple solution.

[diesl]

I think you mean rubocop -a --only Style/For

Sure, I just forgot to change this after c&p a similar issue.

Thanks for fast response and fix 👍