False Positive: Lint/InterpolationCheck

[jfelchner]

Expected behavior

The cop should understand matching things that look like string interpolations inside a Regex

Actual behavior

Matching \#{20} is matching 20 # in a row, not a string interpolation for a variable named 20

Steps to reproduce the problem

# baz.rb
class Foo
  def bar(qux)
    /\#{20}/
  end
end

> rubocop --only='Lint/InterpolationCheck' baz.rb

Output

Inspecting 1 file
W

Offenses:

baz.rb:3:6: W: Lint/InterpolationCheck: Interpolation in single quoted string detected. Use double quoted strings if you need interpolation.
    /\#{20}/
     ^^^^^^

1 file inspected, 1 offense detected

RuboCop version

$ rubocop -V
0.52.1 (using Parser 2.4.0.2, running on ruby 2.4.3 x86_64-darwin16)

[bbatsov]

I also notice that the message Interpolation in single quoted string detected. Use double quoted strings if you need interpolation. violates our policy to have a single-sentence cop messages. We should fix this as well.

[jamiemccarthy]

I'm seeing this too, also with an escaped # in a double-quoted string. My test case is:

Steps to reproduce the problem

root@ac560a15cb0c:/app# cat interp.rb
# frozen_string_literal: true

class Interp # :nodoc:
  my_string = "\#{msg}"
  puts my_string
end
root@ac560a15cb0c:/app# rubocop interp.rb

Output

Inspecting 1 file
W

Offenses:

interp.rb:4:15: W: Lint/InterpolationCheck: Interpolation in single quoted string detected. Use double quoted strings if you need interpolation.
  my_string = "\#{msg}"
              ^^^^^^^^^

1 file inspected, 1 offense detected

RuboCop version

root@ac560a15cb0c:/app# rubocop -V
0.52.1 (using Parser 2.4.0.2, running on ruby 2.3.5 x86_64-linux)