[rubocop#5050] Add Style/TrailingBodyOnClass cop

CHANGELOG.md

@@ -8,6 +8,7 @@
 * [#3666](https://github.com/bbatsov/rubocop/issues/3666): Add new `Naming/UncommunicativeMethodParamName` cop. ([@garettarrowood][])
 * [#5356](https://github.com/bbatsov/rubocop/issues/5356): Add new `Lint/UnneededCopEnableDirective` cop. ([@garettarrowood][])
 * [#5248](https://github.com/bbatsov/rubocop/pull/5248): Add new `Lint/BigDecimalNew` cop. ([@koic][])
+* Add new `Style/TrailingBodyOnClass` cop. ([@garettarrowood][])
 * [#3394](https://github.com/bbatsov/rubocop/issues/3394): Add new `Style/TrailingCommmaInArrayLiteral` cop. ([@garettarrowood][])
 * [#3394](https://github.com/bbatsov/rubocop/issues/3394): Add new `Style/TrailingCommmaInHashLiteral` cop. ([@garettarrowood][])
 * [#5319](https://github.com/bbatsov/rubocop/pull/5319): Add new `Security/Open` cop. ([@mame][])

config/enabled.yml

@@ -1928,6 +1928,10 @@ Style/TernaryParentheses:
   Description: 'Checks for use of parentheses around ternary conditions.'
   Enabled: true
 
+Style/TrailingBodyOnClass:
+  Description: 'Class body goes below class statement.'
+  Enabled: true
+
 Style/TrailingBodyOnMethodDefinition:
   Description: 'Method body goes below definition.'
   Enabled: true

lib/rubocop.rb

@@ -139,6 +139,7 @@
 require_relative 'rubocop/cop/mixin/target_ruby_version'
 require_relative 'rubocop/cop/mixin/target_rails_version'
 require_relative 'rubocop/cop/mixin/too_many_lines'
+require_relative 'rubocop/cop/mixin/trailing_body'
 require_relative 'rubocop/cop/mixin/trailing_comma'
 require_relative 'rubocop/cop/mixin/uncommunicative_name'
 require_relative 'rubocop/cop/mixin/unused_argument'
@@ -503,6 +504,7 @@
 require_relative 'rubocop/cop/style/symbol_literal'
 require_relative 'rubocop/cop/style/symbol_proc'
 require_relative 'rubocop/cop/style/ternary_parentheses'
+require_relative 'rubocop/cop/style/trailing_body_on_class'
 require_relative 'rubocop/cop/style/trailing_body_on_method_definition'
 require_relative 'rubocop/cop/style/trailing_comma_in_arguments'
 require_relative 'rubocop/cop/style/trailing_comma_in_array_literal'

lib/rubocop/cop/correctors/line_break_corrector.rb

@@ -5,7 +5,26 @@ module Cop
     # This class handles autocorrection for code that needs to be moved
     # to new lines.
     class LineBreakCorrector
+      extend Alignment
+      extend TrailingBody
+      extend Util
+
       class << self
+        attr_reader :processed_source
+
+        def correct_trailing_body(configured_width:, corrector:, node:,
+                                  processed_source:)
+          @processed_source = processed_source
+          range = first_part_of(node.to_a.last)
+          eol_comment = end_of_line_comment(node.source_range.line)
+
+          break_line_before(range: range, node: node, corrector: corrector,
+                            configured_width: configured_width)
+          move_comment(eol_comment: eol_comment, node: node,
+                       corrector: corrector)
+          remove_semicolon(node, corrector)
+        end
+
         def break_line_before(range:, node:, corrector:, indent_steps: 1,
                               configured_width:)
           corrector.insert_before(
@@ -22,6 +41,18 @@ def move_comment(eol_comment:, node:, corrector:)
                                   text + "\n" + (' ' * node.loc.keyword.column))
           corrector.remove(eol_comment.loc.expression)
         end
+
+        private
+
+        def remove_semicolon(node, corrector)
+          return unless semicolon(node)
+          corrector.remove(semicolon(node).pos)
+        end
+
+        def semicolon(node)
+          @semicolon ||= {}
+          @semicolon[node.object_id] ||= tokens(node).find(&:semicolon?)
+        end
       end
     end
   end

lib/rubocop/cop/mixin/trailing_body.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    # Common methods shared by TrailingBody cops
+    module TrailingBody
+      def trailing_body?(node)
+        body = node.to_a.reverse[0]
+        body && node.multiline? &&
+          body_on_first_line?(node, body)
+      end
+
+      def body_on_first_line?(node, body)
+        node.source_range.first_line == body.source_range.first_line
+      end
+
+      def first_part_of(body)
+        if body.begin_type?
+          body.children.first.source_range
+        else
+          body.source_range
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/style/trailing_body_on_class.rb

@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Style
+      # This cop checks for trailing code after the class definition.
+      #
+      # @example
+      #   # bad
+      #   class Foo; def foo; end
+      #   end
+      #
+      #   # good
+      #   class Foo
+      #     def foo; end
+      #   end
+      #
+      class TrailingBodyOnClass < Cop
+        include Alignment
+        include TrailingBody
+
+        MSG = 'Place the first line of class body on its own line.'.freeze
+
+        def on_class(node)
+          return unless trailing_body?(node)
+
+          add_offense(node, location: first_part_of(node.to_a.last))
+        end
+
+        def autocorrect(node)
+          lambda do |corrector|
+            LineBreakCorrector.correct_trailing_body(
+              configured_width: configured_indentation_width,
+              corrector: corrector,
+              node: node,
+              processed_source: processed_source
+            )
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/style/trailing_body_on_method_definition.rb

@@ -26,6 +26,7 @@ module Style
       #
       class TrailingBodyOnMethodDefinition < Cop
         include Alignment
+        include TrailingBody
 
         MSG = "Place the first line of a multi-line method definition's " \
               'body on its own line.'.freeze
@@ -39,44 +40,14 @@ def on_def(node)
 
         def autocorrect(node)
           lambda do |corrector|
-            LineBreakCorrector.break_line_before(
-              range: first_part_of(node.body), node: node, corrector: corrector,
-              configured_width: configured_indentation_width
+            LineBreakCorrector.correct_trailing_body(
+              configured_width: configured_indentation_width,
+              corrector: corrector,
+              node: node,
+              processed_source: processed_source
             )
-            LineBreakCorrector.move_comment(
-              eol_comment: end_of_line_comment(node.source_range.line),
-              node: node, corrector: corrector
-            )
-            remove_semicolon(node, corrector)
           end
         end
-
-        private
-
-        def trailing_body?(node)
-          node.body && node.multiline? && on_def_line?(node)
-        end
-
-        def on_def_line?(node)
-          node.source_range.first_line == node.body.source_range.first_line
-        end
-
-        def first_part_of(body)
-          if body.begin_type?
-            body.children.first.source_range
-          else
-            body.source_range
-          end
-        end
-
-        def remove_semicolon(node, corrector)
-          return unless semicolon(node)
-          corrector.remove(semicolon(node).pos)
-        end
-
-        def semicolon(node)
-          @semicolon ||= tokens(node).find(&:semicolon?)
-        end
       end
     end
   end

manual/cops.md

@@ -504,6 +504,7 @@ In the following section you find all available cops:
 * [Style/SymbolLiteral](cops_style.md#stylesymbolliteral)
 * [Style/SymbolProc](cops_style.md#stylesymbolproc)
 * [Style/TernaryParentheses](cops_style.md#styleternaryparentheses)
+* [Style/TrailingBodyOnClass](cops_style.md#styletrailingbodyonclass)
 * [Style/TrailingBodyOnMethodDefinition](cops_style.md#styletrailingbodyonmethoddefinition)
 * [Style/TrailingCommaInArguments](cops_style.md#styletrailingcommainarguments)
 * [Style/TrailingCommaInArrayLiteral](cops_style.md#styletrailingcommainarrayliteral)

manual/cops_style.md

@@ -5370,6 +5370,27 @@ Name | Default value | Configurable values
 EnforcedStyle | `require_no_parentheses` | `require_parentheses`, `require_no_parentheses`, `require_parentheses_when_complex`
 AllowSafeAssignment | `true` | Boolean
 
+## Style/TrailingBodyOnClass
+
+Enabled by default | Supports autocorrection
+--- | ---
+Enabled | Yes
+
+This cop checks for trailing code after the class definition.
+
+### Examples
+
+```ruby
+# bad
+class Foo; def foo; end
+end
+
+# good
+class Foo
+  def foo; end
+end
+```
+
 ## Style/TrailingBodyOnMethodDefinition
 
 Enabled by default | Supports autocorrection

spec/rubocop/cop/style/trailing_body_on_class_spec.rb

@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Style::TrailingBodyOnClass do
+  subject(:cop) { described_class.new(config) }
+
+  let(:config) do
+    RuboCop::Config.new('Layout/IndentationWidth' => { 'Width' => 2 })
+  end
+
+  it 'registers an offense when body trails after class definition' do
+    expect_offense(<<-RUBY.strip_indent)
+      class Foo; body
+                 ^^^^ Place the first line of class body on its own line.
+      end
+      class Bar; def bar; end
+                 ^^^^^^^^^^^^ Place the first line of class body on its own line.
+      end
+    RUBY
+  end
+
+  it 'registers offense with multi-line class' do
+    expect_offense(<<-RUBY.strip_indent)
+      class Foo; body
+                 ^^^^ Place the first line of class body on its own line.
+        def bar
+          qux
+        end
+      end
+    RUBY
+  end
+
+  it 'accepts regular class' do
+    expect_no_offenses(<<-RUBY.strip_indent)
+      class Foo
+        def no_op; end
+      end
+    RUBY
+  end
+
+  it 'accepts class inheritance' do
+    expect_no_offenses(<<-RUBY.strip_indent)
+      class Foo < Bar
+      end
+    RUBY
+  end
+
+  it 'auto-corrects body after class definition' do
+    corrected = autocorrect_source(['class Foo; body ',
+                                    'end'].join("\n"))
+    expect(corrected).to eq ['class Foo ',
+                             '  body ',
+                             'end'].join("\n")
+  end
+
+  it 'auto-corrects with comment after body' do
+    corrected = autocorrect_source(['class BarQux; foo # comment',
+                                    'end'].join("\n"))
+    expect(corrected).to eq ['# comment',
+                             'class BarQux ',
+                             '  foo ',
+                             'end'].join("\n")
+  end
+
+  it 'auto-corrects when there are multiple semicolons' do
+    corrected = autocorrect_source(['class Bar; def bar; end',
+                                    'end'].join("\n"))
+    expect(corrected).to eq ['class Bar ',
+                             '  def bar; end',
+                             'end'].join("\n")
+  end
+
+  context 'when class is not on first line of processed_source' do
+    it 'auto-correct offense' do
+      corrected = autocorrect_source(['',
+                                      '  class Foo; body ',
+                                      '  end'].join("\n"))
+      expect(corrected).to eq ['',
+                               '  class Foo ',
+                               '    body ',
+                               '  end'].join("\n")
+    end
+  end
+end

spec/rubocop/cop/style/trailing_body_on_method_definition_spec.rb

@@ -129,8 +129,8 @@ def some_method
                              '  end'].join("\n")
   end
 
-  context 'when method not on first line of processed_source' do
-    it '' do
+  context 'when method is not on first line of processed_source' do
+    it 'auto-corrects offense' do
       corrected = autocorrect_source(['',
                                       '  def some_method; body',
                                       '  end'].join("\n"))