Add new Style/RedundantDoubleSplatBrackets cop

This cop checks for redundant uses of double splat hash braces. ```ruby # bad do_something(**{foo: bar, baz: qux}) # good do_something(foo: bar, baz: qux) ``` Both are keyword arguments after all.
rubocop · Dec 19, 2022 · 0732939 · 0732939
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diff --git a/changelog/new_add_new_redundant_double_splat_brackets_cop.md b/changelog/new_add_new_redundant_double_splat_brackets_cop.md
@@ -0,0 +1 @@
+* [#11305](https://github.com/rubocop/rubocop/pull/11305): Add new `Style/RedundantDoubleSplatHashBraces` cop. ([@koic][])
diff --git a/config/default.yml b/config/default.yml
@@ -4744,6 +4744,11 @@ Style/RedundantConstantBase:
   Enabled: pending
   VersionAdded: '1.40'
 
+Style/RedundantDoubleSplatHashBraces:
+  Description: 'Checks for redundant uses of double splat hash braces.'
+  Enabled: pending
+  VersionAdded: '<<next>>'
+
 Style/RedundantEach:
   Description: 'Checks for redundant `each`.'
   Enabled: pending

diff --git a/lib/rubocop.rb b/lib/rubocop.rb
@@ -546,6 +546,7 @@
 require_relative 'rubocop/cop/style/operator_method_call'
 require_relative 'rubocop/cop/style/redundant_assignment'
 require_relative 'rubocop/cop/style/redundant_constant_base'
+require_relative 'rubocop/cop/style/redundant_double_splat_hash_braces'
 require_relative 'rubocop/cop/style/redundant_each'
 require_relative 'rubocop/cop/style/redundant_fetch_block'
 require_relative 'rubocop/cop/style/redundant_file_extension_in_require'

diff --git a/lib/rubocop/cop/style/redundant_double_splat_hash_braces.rb b/lib/rubocop/cop/style/redundant_double_splat_hash_braces.rb
@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Style
+      # Checks for redundant uses of double splat hash braces.
+      #
+      # @example
+      #
+      #   # bad
+      #   do_something(**{foo: bar, baz: qux})
+      #
+      #   # good
+      #   do_something(foo: bar, baz: qux)
+      #
+      class RedundantDoubleSplatHashBraces < Base
+        extend AutoCorrector
+
+        MSG = 'Remove the redundant double splat and braces, use keyword arguments directly.'
+
+        # @!method double_splat_hash_braces?(node)
+        def_node_matcher :double_splat_hash_braces?, <<~PATTERN
+          (hash (kwsplat (hash ...)))
+        PATTERN
+
+        def on_hash(node)
+          return if node.pairs.empty? || node.pairs.any?(&:hash_rocket?)
+
+          grandparent = node.parent&.parent
+          return unless double_splat_hash_braces?(grandparent)
+
+          add_offense(grandparent) do |corrector|
+            corrector.replace(grandparent, node.pairs.map(&:source).join(', '))
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/rubocop/cop/style/redundant_double_splat_hash_braces_spec.rb b/spec/rubocop/cop/style/redundant_double_splat_hash_braces_spec.rb
@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Style::RedundantDoubleSplatHashBraces, :config do
+  it 'registers an offense when using double splat hash braces' do
+    expect_offense(<<~RUBY)
+      do_something(**{foo: bar, baz: qux})
+                   ^^^^^^^^^^^^^^^^^^^^^^ Remove the redundant double splat and braces, use keyword arguments directly.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      do_something(foo: bar, baz: qux)
+    RUBY
+  end
+
+  it 'does not register an offense when using keyword arguments' do
+    expect_no_offenses(<<~RUBY)
+      do_something(foo: bar, baz: qux)
+    RUBY
+  end
+
+  it 'does not register an offense when using empty double splat hash braces arguments' do
+    expect_no_offenses(<<~RUBY)
+      do_something(**{})
+    RUBY
+  end
+
+  it 'does not register an offense when using hash rocket double splat hash braces arguments' do
+    expect_no_offenses(<<~RUBY)
+      do_something(**{foo => bar})
+    RUBY
+  end
+
+  it 'does not register an offense when using method call for double splat hash braces arguments' do
+    expect_no_offenses(<<~RUBY)
+      do_something(**{foo: bar}.merge(options))
+    RUBY
+  end
+
+  it 'does not register an offense when using hash braces arguments' do
+    expect_no_offenses(<<~RUBY)
+      do_something({foo: bar, baz: qux})
+    RUBY
+  end
+
+  it 'does not register an offense when using double splat variable' do
+    expect_no_offenses(<<~RUBY)
+      do_something(**h)
+    RUBY
+  end
+
+  it 'does not register an offense when using hash literal' do
+    expect_no_offenses(<<~RUBY)
+      { a: a }
+    RUBY
+  end
+end
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		* [#11305](https://github.com/rubocop/rubocop/pull/11305): Add new `Style/RedundantDoubleSplatHashBraces` cop. ([@koic][])