autocorrect removes negation

[tbhi]

With file containing:

def get_m3u8_lines_from(manifest_body)
  manifest_body.each_line.map(&:strip).reject(&:empty?).select{|line| (not line.start_with? '#') }
end

Running autocorrect:

$ rubocop -V
0.66.0 (using Parser 2.5.3.0, running on ruby 2.6.2 x86_64-darwin18)
$ rubocop -a ~/Downloads/manifest.rb
Inspecting 1 file
C

Offenses:

Downloads/manifest.rb:2:3: C: [Corrected] Style/InverseMethods: Use reject instead of inverting select.
  manifest_body.each_line.map(&:strip).reject(&:empty?).select{|line| (not line.start_with? '#') }
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Downloads/manifest.rb:2:3: C: [Corrected] Style/InverseMethods: Use select instead of inverting reject.
  manifest_body.each_line.map(&:strip).reject(&:empty?).reject {|line| (!line.start_with? '#') }
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Downloads/manifest.rb:2:63: C: [Corrected] Layout/SpaceBeforeBlockBraces: Space missing to the left of {.
  manifest_body.each_line.map(&:strip).reject(&:empty?).select{|line| (not line.start_with? '#') }
                                                              ^
Downloads/manifest.rb:2:63: C: [Corrected] Layout/SpaceInsideBlockBraces: Space between { and | missing.
  manifest_body.each_line.map(&:strip).reject(&:empty?).select{|line| (not line.start_with? '#') }
                                                              ^^
Downloads/manifest.rb:2:64: C: [Corrected] Layout/SpaceInsideBlockBraces: Space between { and | missing.
  manifest_body.each_line.map(&:strip).reject(&:empty?).reject {|line| (!line.start_with? '#') }
                                                               ^^
Downloads/manifest.rb:2:72: C: [Corrected] Style/Not: Use ! instead of not.
  manifest_body.each_line.map(&:strip).reject(&:empty?).select{|line| (not line.start_with? '#') }
                                                                       ^^^
Downloads/manifest.rb:2:81: C: Metrics/LineLength: Line is too long. [96/80]
  manifest_body.each_line.map(&:strip).reject(&:empty?).select { |line| (line.start_with? '#') }
                                                                                ^^^^^^^^^^^^^^^^

1 file inspected, 7 offenses detected, 6 offenses corrected

Ends up losing the negation in the output:

def get_m3u8_lines_from(manifest_body)
  manifest_body.each_line.map(&:strip).reject(&:empty?).select { |line| (line.start_with? '#') }
end

[dduugg]

In case useful, a more minimal repro:

x.select {|y| not y.z}

is autocorrected to

x.select(&:z)

using rubocop defaults

[hoshinotsuyoshi]

The comment #6860 (comment) is so helpful to me. thank you! @dduugg

I believe that the problem is that Style/InverseMethods cop and Style/Not cop combination cannot auto-correct such code at once.

file:

x.select { |y| not y.z }

auto-correct:

$ bundle exec rubocop -a c.rb --only Style/InverseMethods,Style/Not
Inspecting 1 file
C

Offenses:

c.rb:1:1: C: [Corrected] Style/InverseMethods: Use reject instead of inverting select.
x.select { |y| not y.z }
^^^^^^^^^^^^^^^^^^^^^^^^
c.rb:1:1: C: [Corrected] Style/InverseMethods: Use select instead of inverting reject.
x.reject { |y| !y.z }
^^^^^^^^^^^^^^^^^^^^^
c.rb:1:16: C: [Corrected] Style/Not: Use ! instead of not.
x.select { |y| not y.z }
               ^^^

1 file inspected, 3 offenses detected, 3 offenses corrected

corrected badly:

x.select { |y| y.z }