Lint/UnneededSplatExpansion: wrong unnecessary splat expansion.

[victorfeijo]

---

Expected behaviour

Hello! I'm having a issue with Rubocop warning this code:

[*'A'..'H', *%w(J K M N), *'P'..'Z', *'0'..'9'] Unnecessary splat expansion in *%w(J K M N)

Which gives me something like ['A', 'B', 'C', 'D' 'E' .. 'J', 'K', 'M', 'N', 'P' .. '0', .. '9'].

Actual behaviour

When i use rubocop -a filename , the cop just removes the * from *%w(J K M N) and the returned data appears to be something different like:

['A', 'B', 'C', ['J', K', 'M', 'N'], 'P' ... '0']

It creates a new array inside. I'm trying # disable instead but would be good if i could keep both running, rubocop and *%w(J K M N)

RuboCop version

$ rubocop -V
0.44.1

[tejasbubane]

I tried putting together a bugfix, but came across this:

[1] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node.source
=> "[*[1, 2, 3, 4, 5]]"
[2] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node
=> s(:array,
  s(:splat,
    s(:array,
      s(:int, 1),
      s(:int, 2),
      s(:int, 3),
      s(:int, 4),
      s(:int, 5))))

[1] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node.source
=> "*[1, 2, 3]"
[2] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node
=> s(:array,
  s(:splat,
    s(:array,
      s(:int, 1),
      s(:int, 2),
      s(:int, 3))))

This^ should be splat-array instead of array-splat-array. Is this some issue with the parser?

[rrosenblum]

@tejasbubane, I am not seeing the same issue with the code parsing that you are with the given example. What are versions of parser and ruby that you are using? Mine are 0.44.1 (using Parser 2.3.1.4, running on ruby 2.3.1 x86_64-darwin14).

[9] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node.source
=> "*[1, 2, 3]"
[10] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node
=> s(:splat,
  s(:array,
    s(:int, 1),
    s(:int, 2),
    s(:int, 3)))
[11] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node.parent.source
=> "[*[1, 2, 3]]"
[12] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node.parent
=> s(:array,
  s(:splat,
    s(:array,
      s(:int, 1),
      s(:int, 2),
      s(:int, 3))))

I was able to reproduce what you saw with the foo = *[1, 2, 3]. In this case, I assume that the array-splat-array has something to do with how Ruby will treat the array once it has been expanded.

[1] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node.source
=> "*[1, 2, 3]"
[2] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node
=> s(:splat,
  s(:array,
    s(:int, 1),
    s(:int, 2),
    s(:int, 3)))
[3] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node.parent.source
=> "*[1, 2, 3]"
[4] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node.parent
=> s(:array,
  s(:splat,
    s(:array,
      s(:int, 1),
      s(:int, 2),
      s(:int, 3))))
[5] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node.parent.parent.source
=> "foo = *[1, 2, 3]"
[6] pry(#<RuboCop::Cop::Lint::UnneededSplatExpansion>)> node.parent.parent
=> s(:lvasgn, :foo,
  s(:array,
    s(:splat,
      s(:array,
        s(:int, 1),
        s(:int, 2),
        s(:int, 3)))))

@victorfeijo, this doesn't look like it will be difficult to fix. We just need to change the correction if we are in an array.