Properly auto-correct percent arrays in CaseWhenSplat

MeetMe · Sep 17, 2015 · 8eedad3 · 8eedad3
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -10,6 +10,7 @@
 * [#2240](https://github.com/bbatsov/rubocop/pull/2240): `Lint/UnneededDisable` should not report non-`Lint` `rubocop:disable` comments when running `rubocop --lint`. ([@jonas054][])
 * [#2121](https://github.com/bbatsov/rubocop/issues/2121): Allow space before values in hash literals in `Style/ExtraSpacing` to avoid correction conflict. ([@jonas054][])
 * [#2241](https://github.com/bbatsov/rubocop/issues/2241): Read cache in binary format. ([@jonas054][])
+* [#2247](https://github.com/bbatsov/rubocop/issues/2247): Fix auto-correct of `Performance/CaseWhenSplat` for percent arrays (`%w`, `%W`, `%i`, and `%I`). ([@rrosenblum][])
 
 ### Changes
 

diff --git a/lib/rubocop/cop/performance/case_when_splat.rb b/lib/rubocop/cop/performance/case_when_splat.rb
@@ -56,6 +56,11 @@ class CaseWhenSplat < Cop
         MSG = 'Place `when` conditions with a splat ' \
               'at the end of the `when` branches.'.freeze
         ARRAY_MSG = 'Do not expand array literals in `when` conditions.'.freeze
+        OPEN_BRACKET = '['.freeze
+        PERCENT_W = '%w'.freeze
+        PERCENT_CAPITAL_W = '%W'.freeze
+        PERCENT_I = '%i'.freeze
+        PERCENT_CAPITAL_I = '%I'.freeze
 
         def on_case(node)
           _case_branch, *when_branches, _else_branch = *node
@@ -104,9 +109,16 @@ def error_condition?(condition)
 
         def correct_array_literal(condition, variable)
           lambda do |corrector|
-            corrector.remove(condition.loc.operator)
-            corrector.remove(variable.loc.begin)
-            corrector.remove(variable.loc.end)
+            array_start = variable.loc.begin.source
+
+            if array_start.start_with?(OPEN_BRACKET)
+              corrector.remove(condition.loc.operator)
+              corrector.remove(variable.loc.begin)
+              corrector.remove(variable.loc.end)
+            else
+              corrector.replace(condition.loc.expression,
+                                expand_percent_array(variable))
+            end
           end
         end
 
@@ -126,6 +138,22 @@ def reorder_splat_condition(node)
                                    correction)
           end
         end
+
+        def expand_percent_array(array)
+          array_start = array.loc.begin.source
+          elements = *array
+          elements = elements.map { |e| e.loc.expression.source }
+
+          if array_start.start_with?(PERCENT_W)
+            "'#{elements.join("', '")}'"
+          elsif array_start.start_with?(PERCENT_CAPITAL_W)
+            %("#{elements.join('", "')}")
+          elsif array_start.start_with?(PERCENT_I)
+            ":#{elements.join(', :')}"
+          elsif array_start.start_with?(PERCENT_CAPITAL_I)
+            %(:"#{elements.join('", :"')}")
+          end
+        end
       end
     end
   end

diff --git a/spec/rubocop/cop/performance/case_when_splat_spec.rb b/spec/rubocop/cop/performance/case_when_splat_spec.rb
@@ -298,5 +298,91 @@
                                 '  bar',
                                 'end'].join("\n"))
     end
+
+    it 'corrects splat on array literals using %w' do
+      new_source = autocorrect_source(cop, ['case foo',
+                                            'when *%w(first second)',
+                                            '  baz',
+                                            'end'])
+
+      expect(new_source).to eq(['case foo',
+                                "when 'first', 'second'",
+                                '  baz',
+                                'end'].join("\n"))
+    end
+
+    it 'corrects splat on array literals using %W' do
+      new_source = autocorrect_source(cop, ['case foo',
+                                            'when *%W(#{first} #{second})',
+                                            '  baz',
+                                            'end'])
+
+      expect(new_source).to eq(['case foo',
+                                'when "#{first}", "#{second}"',
+                                '  baz',
+                                'end'].join("\n"))
+    end
+
+    context 'ruby >= 2.0', ruby_greater_than_or_equal: 2.0 do
+      it 'corrects splat on array literals using %i' do
+        new_source = autocorrect_source(cop, ['case foo',
+                                              'when *%i(first second)',
+                                              '  baz',
+                                              'end'])
+
+        expect(new_source).to eq(['case foo',
+                                  'when :first, :second',
+                                  '  baz',
+                                  'end'].join("\n"))
+      end
+
+      it 'corrects splat on array literals using %I' do
+        new_source = autocorrect_source(cop, ['case foo',
+                                              'when *%I(#{first} #{second})',
+                                              '  baz',
+                                              'end'])
+
+        expect(new_source).to eq(['case foo',
+                                  'when :"#{first}", :"#{second}"',
+                                  '  baz',
+                                  'end'].join("\n"))
+      end
+
+      it 'corrects everything at once' do
+        new_source = autocorrect_source(cop, ['case foo',
+                                              'when *bar',
+                                              '  1',
+                                              'when baz',
+                                              '  2',
+                                              "when *['a', 'b']",
+                                              '  3',
+                                              'when *%w(c d)',
+                                              '  4',
+                                              'when *%W(#{e} #{f})',
+                                              '  5',
+                                              'when *%i(g h)',
+                                              '  6',
+                                              'when *%I(#{i} #{j})',
+                                              '  7',
+                                              'end'])
+
+        expect(new_source).to eq(['case foo',
+                                  'when baz',
+                                  '  2',
+                                  "when 'a', 'b'",
+                                  '  3',
+                                  "when 'c', 'd'",
+                                  '  4',
+                                  'when "#{e}", "#{f}"',
+                                  '  5',
+                                  'when :g, :h',
+                                  '  6',
+                                  'when :"#{i}", :"#{j}"',
+                                  '  7',
+                                  'when *bar',
+                                  '  1',
+                                  'end'].join("\n"))
+      end
+    end
   end
 end