[Fix rubocop#7705] Fix Style/OneLineConditional to handle if/then/e…

…lsif/then/else and add AlwaysCorrectToMultiline config option

CHANGELOG.md

@@ -23,6 +23,7 @@
 * [#8524](https://github.com/rubocop-hq/rubocop/issues/8524): Fix `Layout/EmptyLinesAroundClassBody`  and `Layout/EmptyLinesAroundModuleBody` to correctly handle an access modifier as a first child. ([@dsavochkin][])
 * [#8518](https://github.com/rubocop-hq/rubocop/issues/8518): Fix `Lint/ConstantResolution` cop reporting offense for `module` and `class` definitions. ([@tejasbubane][])
 * [#8158](https://github.com/rubocop-hq/rubocop/issues/8158): Fix `Style/MultilineWhenThen` cop to correctly handle cases with multiline body. ([@dsavochkin][])
+* [#7705](https://github.com/rubocop-hq/rubocop/issues/7705): Fix `Style/OneLineConditional` cop to handle if/then/elsif/then/else/end cases. Add `AlwaysCorrectToMultiline` config option to this cop to always convert offenses to the multi-line form (false by default). ([@Lykos][], [@dsavochkin][])
 
 ### Changes
 
@@ -4804,3 +4805,4 @@
 [@wcmonty]: https://github.com/wcmonty
 [@nguyenquangminh0711]: https://github.com/nguyenquangminh0711
 [@chocolateboy]: https://github.com/chocolateboy
+[@Lykos]: https://github.com/Lykos

config/default.yml

@@ -3636,12 +3636,13 @@ Style/NumericPredicate:
 
 Style/OneLineConditional:
   Description: >-
-                 Favor the ternary operator(?:) over
-                 if/then/else/end constructs.
+                 Favor the ternary operator (?:) or multi-line constructs over
+                 single-line if/then/else/end constructs.
   StyleGuide: '#ternary-operator'
   Enabled: true
+  AlwaysCorrectToMultiline: false
   VersionAdded: '0.9'
-  VersionChanged: '0.38'
+  VersionChanged: '0.90'
 
 Style/OptionHash:
   Description: "Don't use option hashes when you can use keyword arguments."

docs/modules/ROOT/pages/cops_style.adoc

@@ -6665,33 +6665,51 @@ bar.baz > 0
 | Yes
 | Yes
 | 0.9
-| 0.38
+| 0.90
 |===
 
-TODO: Make configurable.
-Checks for uses of if/then/else/end on a single line.
+Checks for uses of if/then/else/end constructs on a single line.
+AlwaysCorrectToMultiline config option can be set to true to auto-convert all offenses to
+multi-line constructs. When AlwaysCorrectToMultiline is false (default case) the
+auto-correct will first try converting them to ternary operators.
 
 === Examples
 
 [source,ruby]
 ----
 # bad
-if foo then boo else doo end
-unless foo then boo else goo end
+if foo then bar else baz end
+
+# bad
+unless foo then baz else bar end
+
+# good
+foo ? bar : baz
 
 # good
-foo ? boo : doo
-boo if foo
-if foo then boo end
+bar if foo
+
+# good
+if foo then bar end
 
 # good
 if foo
-  boo
+  bar
 else
-  doo
+  baz
 end
 ----
 
+=== Configurable attributes
+
+|===
+| Name | Default value | Configurable values
+
+| AlwaysCorrectToMultiline
+| `false`
+| Boolean
+|===
+
 === References
 
 * https://rubystyle.guide#ternary-operator

lib/rubocop/cop/style/one_line_conditional.rb

@@ -3,34 +3,45 @@
 module RuboCop
   module Cop
     module Style
-      # TODO: Make configurable.
-      # Checks for uses of if/then/else/end on a single line.
+      # Checks for uses of if/then/else/end constructs on a single line.
+      # AlwaysCorrectToMultiline config option can be set to true to auto-convert all offenses to
+      # multi-line constructs. When AlwaysCorrectToMultiline is false (default case) the
+      # auto-correct will first try converting them to ternary operators.
       #
       # @example
       #   # bad
-      #   if foo then boo else doo end
-      #   unless foo then boo else goo end
+      #   if foo then bar else baz end
+      #
+      #   # bad
+      #   unless foo then baz else bar end
+      #
+      #   # good
+      #   foo ? bar : baz
       #
       #   # good
-      #   foo ? boo : doo
-      #   boo if foo
-      #   if foo then boo end
+      #   bar if foo
+      #
+      #   # good
+      #   if foo then bar end
       #
       #   # good
       #   if foo
-      #     boo
+      #     bar
       #   else
-      #     doo
+      #     baz
       #   end
       class OneLineConditional < Base
+        include ConfigurableEnforcedStyle
         include OnNormalIfUnless
         extend AutoCorrector
 
-        MSG = 'Favor the ternary operator (`?:`) ' \
-              'over `%<keyword>s/then/else/end` constructs.'
+        MSG = 'Favor the ternary operator (`?:`) or multi-line constructs ' \
+              'over single-line `%<keyword>s/then/else/end` constructs.'
 
         def on_normal_if_unless(node)
-          return unless node.single_line? && node.else_branch
+          return unless node.single_line?
+          return unless node.else_branch
+          return if node.elsif?
 
           message = message(node)
           add_offense(node, message: message) do |corrector|
@@ -45,16 +56,55 @@ def message(node)
         end
 
         def replacement(node)
-          return to_ternary(node) unless node.parent
+          if always_multiline? || cannot_replace_to_ternary?(node)
+            multiline_replacement(node)
+          else
+            replaced_node = ternary_replacement(node)
+            return replaced_node unless node.parent
+            return "(#{replaced_node})" if %i[and or].include?(node.parent.type)
+            return "(#{replaced_node})" if node.parent.send_type? && node.parent.operator_method?
+
+            replaced_node
+          end
+        end
 
-          return "(#{to_ternary(node)})" if %i[and or].include?(node.parent.type)
+        def always_multiline?
+          @config.for_cop('Style/OneLineConditional')['AlwaysCorrectToMultiline']
+        end
+
+        def cannot_replace_to_ternary?(node)
+          node.elsif_conditional?
+        end
 
-          return "(#{to_ternary(node)})" if node.parent.send_type? && node.parent.operator_method?
+        def multiline_replacement(node, indentation = nil)
+          indentation = ' ' * node.source_range.column if indentation.nil?
+          if_branch_source = node.if_branch&.source || 'nil'
+          elsif_indentation = indentation if node.respond_to?(:elsif?) && node.elsif?
+          if_branch = <<~RUBY
+            #{elsif_indentation}#{node.keyword} #{node.condition.source}
+            #{indentation}#{branch_body_indentation}#{if_branch_source}
+          RUBY
+          else_branch = else_branch_to_multiline(node.else_branch, indentation)
+          if_branch + else_branch
+        end
+
+        def else_branch_to_multiline(else_branch, indentation)
+          if else_branch.if_type? && else_branch.elsif?
+            multiline_replacement(else_branch, indentation)
+          else
+            <<~RUBY.chomp
+              #{indentation}else
+              #{indentation}#{branch_body_indentation}#{else_branch.source}
+              #{indentation}end
+            RUBY
+          end
+        end
 
-          to_ternary(node)
+        def branch_body_indentation
+          ' ' * (@config.for_cop('Layout/IndentationWidth')['Width'] || 2)
         end
 
-        def to_ternary(node)
+        def ternary_replacement(node)
           condition, if_branch, else_branch = *node
 
           "#{expr_replacement(condition)} ? " \

spec/rubocop/cli_spec.rb

@@ -175,8 +175,8 @@ def and_with_args
                 "if it's surely a splat operator, or add a whitespace to the " \
                 'right of the `*` if it should be a multiplication.',
                 "#{abs('example.rb')}:4:1: C: Style/OneLineConditional: " \
-                'Favor the ternary operator (`?:`) over `if/then/else/end` ' \
-                'constructs.',
+                'Favor the ternary operator (`?:`) or multi-line constructs over ' \
+                'single-line `if/then/else/end` constructs.',
                 ''].join("\n"))
     end
   end