Style/RedundantDoubleSplatHashBraces incorrect Autofix

[mseedat-moj]

When upgrading to rubocop 1.57.1, splat arguments can be flagged by the Style/RedundantDoubleSplatHashBraces. Running rubocop -A for autofixing the problem introduced incorrect code.

---

Expected behavior

Autofix should not try to simplifiy code that has list operations on a part of the argument list, in the example below .compact_blank should be applied to the resulting merge hash.

Actual behavior

Given the following code:

def client
  @client ||= Aws::S3::Client.new(
     **{ endpoint: }.merge(default_client_cfg).compact_blank
  )
end

Then running:

rubocop -A --debug

Results in:

<path:linenumber>: C: [Corrected] Style/RedundantDoubleSplatHashBraces: Remove the redundant double splat and braces, use keyword arguments directly.
            **{ ...
            ^^^

And the new code:

def client
  @client ||= Aws::S3::Client.new(
    endpoint:, **default_client_cfg.compact_blank
  )
end

Steps to reproduce the problem

You can run code similar to the above to reproduce the problem.

You can see the Autofix output from Rubocop is not functionally equivalent to the original by running the following code snippet in Rails console/ IRB:

class Rubbish
  def initialize(**args)
    puts args.inspect
  end
end
def endpoint; @endpoint; end;

@endpoint = 'https'
default_client_cfg = {:name=>"mo", :last=>nil, :endpoint=>""}


# Original:
Rubbish.new( **{endpoint:}.merge(default_client_cfg).compact_blank )
# Result > {:name=>"mo"}

# Rubocop autofix:
Rubbish.new( endpoint:, **default_client_cfg.compact_blank )
# Result > {:endpoint=>"http", :name=>"mo"}

RuboCop version

Include the output of rubocop -V or bundle exec rubocop -V if using Bundler.
If you see extension cop versions (e.g. rubocop-performance, rubocop-rspec, and others)
output by rubocop -V, include them as well. Here's an example:

$ [bundle exec] rubocop -V
1.57.1 (using Parser 3.2.2.4, rubocop-ast 1.29.0, running on ruby 3.2.2) [x86_64-darwin22]
  - rubocop-performance 1.19.1
  - rubocop-rails 2.21.2
  - rubocop-rspec 2.24.1