Bug #12851: string.gsub!(/\W/, '').downcase! returns undefined method in some (listed) cases

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin16]
• Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN

[ciscoved (Mikhail A)]

Hi! Found this strange issue with gsub! and downcase! methods used together for a string. Example code:

def palindrome? (str)
  str.gsub!(/\W/, '').downcase!
  str == str.reverse
end

puts palindrome?("Madam, I'm Adam!")

returns true. Ok! But...!

if the given string is single word:

def palindrome? (str)
  str.gsub!(/\W/, '').downcase!
  str == str.reverse
end

puts palindrome?("aBba")

it returns no method error.

hw1_string.rb:13:in palindrome?': undefined method downcase!' for nil:NilClass (NoMethodError)
from hw1_string.rb:30:in `'

If the code is refactored like this:

def palindrome? (str)
  str.gsub!(/\W/, '')
  str.downcase!
  str == str.reverse
end

puts palindrome?("abba")
puts palindrome?("Madam, I'm Adam!")

than it worked ok in both cases. Why?

I'm new to ruby, and, may be still misunderstood something, but seems that is really a bug.

[ciscoved (Mikhail A)]

• Description updated (diff)

[ciscoved (Mikhail A)]

• Description updated (diff)

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Rejected

This isn't a bug. String#gsub! returns nil if no changes are made. From the documentation for String#gsub!: "Performs the substitutions of String#gsub in place, returning str, or nil if no substitutions were performed."