Add Style/EmptyLineAfterMagicComment cop

Depends on rubocop/ruby-style-guide#616
rubocop · Jan 24, 2017 · e17fecf · e17fecf
1 parent 2e70d6f
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### New features
 
 * [#3893](https://github.com/bbatsov/rubocop/issues/3893): Add a new configuration, `IncludeActiveSupportAliases`, to `Performance/DoublStartEndWith`. This configuration will check for ActiveSupport's `starts_with?` and `ends_with?`. ([@rrosenblum][])
+* [#3889](https://github.com/bbatsov/rubocop/pull/3889): Add new `Style/EmptyLineAfterMagicComment` cop. ([@backus][])
 
 ### Changes
 

diff --git a/config/enabled.yml b/config/enabled.yml
@@ -533,6 +533,11 @@ Style/NestedTernaryOperator:
   StyleGuide: '#no-nested-ternary'
   Enabled: true
 
+Style/EmptyLineAfterMagicComment:
+  Description: 'Add a newline after magic comments to separate them from code.'
+  StyleGuide: '#separate-magic-comments-from-code'
+  Enabled: true
+
 Style/Next:
   Description: 'Use `next` to skip iteration instead of a condition at the end.'
   StyleGuide: '#no-nested-conditionals'

diff --git a/lib/rubocop.rb b/lib/rubocop.rb
@@ -257,6 +257,7 @@
 require 'rubocop/cop/style/else_alignment'
 require 'rubocop/cop/style/empty_case_condition'
 require 'rubocop/cop/style/empty_else'
+require 'rubocop/cop/style/empty_line_after_magic_comment'
 require 'rubocop/cop/style/empty_line_between_defs'
 require 'rubocop/cop/style/empty_lines'
 require 'rubocop/cop/style/empty_lines_around_access_modifier'

diff --git a/lib/rubocop/cop/bundler/ordered_gems.rb b/lib/rubocop/cop/bundler/ordered_gems.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 module RuboCop
   module Cop
     module Bundler

diff --git a/lib/rubocop/cop/cop.rb b/lib/rubocop/cop/cop.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 require 'uri'
 
 module RuboCop

diff --git a/lib/rubocop/cop/style/documentation_method.rb b/lib/rubocop/cop/style/documentation_method.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 module RuboCop
   module Cop
     module Style

diff --git a/lib/rubocop/cop/style/empty_line_after_magic_comment.rb b/lib/rubocop/cop/style/empty_line_after_magic_comment.rb
@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Style
+      # Checks for a newline after the final magic comment.
+      #
+      # @example
+      #   # good
+      #   # frozen_string_literal: true
+      #
+      #   # Some documentation for Person
+      #   class Person
+      #     # Some code
+      #   end
+      #
+      #   # bad
+      #   # frozen_string_literal: true
+      #   # Some documentation for Person
+      #   class Person
+      #     # Some code
+      #   end
+      class EmptyLineAfterMagicComment < Cop
+        MSG = 'Add a space after magic comments.'.freeze
+        BLANK_LINE = /\A\s*\z/
+
+        def investigate(source)
+          return unless source.ast &&
+                        (last_magic_comment = last_magic_comment(source))
+          return if source[last_magic_comment.loc.line] =~ BLANK_LINE
+
+          offending_range =
+            source_range(source.buffer, last_magic_comment.loc.line + 1, 0)
+
+          add_offense(offending_range, offending_range)
+        end
+
+        def autocorrect(token)
+          lambda do |corrector|
+            corrector.insert_before(token, "\n")
+          end
+        end
+
+        private
+
+        # Find the last magic comment in the source file.
+        #
+        # Take all comments that precede the first line of code, select the
+        # magic comments, and return the last magic comment in the file.
+        #
+        # @return [Parser::Source::Comment] if magic comments exist before code
+        # @return [nil] otherwise
+        def last_magic_comment(source)
+          source
+            .comments
+            .take_while { |comment| comment.loc.line < source.ast.loc.line }
+            .select     { |comment| MagicComment.parse(comment.text).any?  }
+            .last
+        end
+      end
+    end
+  end
+end
diff --git a/lib/rubocop/cop/style/stabby_lambda_parentheses.rb b/lib/rubocop/cop/style/stabby_lambda_parentheses.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 module RuboCop
   module Cop
     module Style

diff --git a/lib/rubocop/cop/util.rb b/lib/rubocop/cop/util.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
-# rubocop:disable Metrics/ModuleLength
 
+# rubocop:disable Metrics/ModuleLength
 module RuboCop
   module Cop
     # This module contains a collection of useful utility methods.

diff --git a/lib/rubocop/magic_comment.rb b/lib/rubocop/magic_comment.rb
@@ -26,6 +26,10 @@ def initialize(comment)
       @comment = comment
     end
 
+    def any?
+      frozen_string_literal_specified? || encoding_specified?
+    end
+
     # Does the magic comment enable the frozen string literal feature.
     #
     # Test whether the frozen string literal value is `true`. Cannot
@@ -42,7 +46,7 @@ def frozen_string_literal?
     #
     # @return [Boolean]
     def frozen_string_literal_specified?
-      !frozen_string_literal.nil?
+      specified?(frozen_string_literal)
     end
 
     # Expose the `frozen_string_literal` value coerced to a boolean if possible.
@@ -61,8 +65,16 @@ def frozen_string_literal
       end
     end
 
+    def encoding_specified?
+      specified?(encoding)
+    end
+
     private
 
+    def specified?(value)
+      !value.nil?
+    end
+
     # Match the entire comment string with a pattern and take the first capture.
     #
     # @param pattern [Regexp]

diff --git a/manual/cops.md b/manual/cops.md
@@ -255,6 +255,7 @@ In the following section you find all available cops:
 * [Style/ElseAlignment](cops_style.md#styleelsealignment)
 * [Style/EmptyCaseCondition](cops_style.md#styleemptycasecondition)
 * [Style/EmptyElse](cops_style.md#styleemptyelse)
+* [Style/EmptyLineAfterMagicComment](cops_style.md#styleemptylineaftermagiccomment)
 * [Style/EmptyLineBetweenDefs](cops_style.md#styleemptylinebetweendefs)
 * [Style/EmptyLines](cops_style.md#styleemptylines)
 * [Style/EmptyLinesAroundAccessModifier](cops_style.md#styleemptylinesaroundaccessmodifier)

diff --git a/manual/cops_style.md b/manual/cops_style.md
@@ -1217,6 +1217,33 @@ EnforcedStyle | both
 SupportedStyles | empty, nil, both
 
 
+## Style/EmptyLineAfterMagicComment
+
+Enabled by default | Supports autocorrection
+--- | ---
+Enabled | Yes
+
+Checks for a newline after the final magic comment.
+
+### Example
+
+```ruby
+# good
+# frozen_string_literal: true
+
+# Some documentation for Person
+class Person
+  # Some code
+end
+
+# bad
+# frozen_string_literal: true
+# Some documentation for Person
+class Person
+  # Some code
+end
+```
+
 ## Style/EmptyLineBetweenDefs
 
 Enabled by default | Supports autocorrection

diff --git a/spec/rubocop/cli/cli_auto_gen_config_spec.rb b/spec/rubocop/cli/cli_auto_gen_config_spec.rb
@@ -86,6 +86,7 @@
                                   'y ',
                                   'puts x'])
       create_file('example2.rb', ['# encoding: utf-8',
+                                  '',
                                   "\tx = 0",
                                   'puts x',
                                   '',
@@ -189,6 +190,7 @@
                                   'y ',
                                   'puts x'])
       create_file('example2.rb', ['# encoding: utf-8',
+                                  '',
                                   '#' * 85,
                                   "\tx = 0",
                                   'puts x'])
@@ -266,9 +268,11 @@
 
     it 'does not generate configuration for the Syntax cop' do
       create_file('example1.rb', ['# encoding: utf-8',
+                                  '',
                                   'x = < ', # Syntax error
                                   'puts x'])
       create_file('example2.rb', ['# encoding: utf-8',
+                                  '',
                                   "\tx = 0",
                                   'puts x'])
       expect(cli.run(['--auto-gen-config'])).to eq(1)
@@ -364,6 +368,7 @@
                                   'y ',
                                   'puts x'])
       create_file('example2.rb', ['# encoding: utf-8',
+                                  '',
                                   "\tx = 0",
                                   'puts x',
                                   '',

diff --git a/spec/rubocop/cli/cli_options_spec.rb b/spec/rubocop/cli/cli_options_spec.rb
@@ -717,6 +717,7 @@ def full_description_of_cop(cop)
                                       'y ',
                                       'puts x'])
           create_file('example2.rb', ['# encoding: utf-8',
+                                      '',
                                       "\tx",
                                       'def a',
                                       '   puts',
@@ -749,18 +750,18 @@ def full_description_of_cop(cop)
                     ' (column 0 instead of 1).',
                     '# encoding: utf-8',
                     '^^^^^^^^^^^^^^^^^',
-                    'example2.rb:2:1: C: Tab detected.',
+                    'example2.rb:3:1: C: Tab detected.',
                     "\tx",
                     '^',
-                    'example2.rb:2:2: C: Indentation of first line in file ' \
+                    'example2.rb:3:2: C: Indentation of first line in file ' \
                     'detected.',
                     "\tx",
                     ' ^',
-                    'example2.rb:3:1: C: Inconsistent indentation ' \
+                    'example2.rb:4:1: C: Inconsistent indentation ' \
                     'detected.',
                     'def a ...',
                     '^^^^^',
-                    'example2.rb:4:1: C: Use 2 (not 3) spaces for ' \
+                    'example2.rb:5:1: C: Use 2 (not 3) spaces for ' \
                     'indentation.',
                     '   puts',
                     '^^^',
@@ -789,25 +790,27 @@ def full_description_of_cop(cop)
       context 'when emacs format is specified' do
         it 'outputs with emacs format' do
           create_file('example1.rb', ['# encoding: utf-8',
+                                      '',
                                       'x= 0 ',
                                       'y ',
                                       'puts x'])
           create_file('example2.rb', ['# encoding: utf-8',
+                                      '',
                                       "\tx = 0",
                                       'puts x'])
           expect(cli.run(['--format', 'emacs', 'example1.rb',
                           'example2.rb'])).to eq(1)
           expected_output =
-            ["#{abs('example1.rb')}:2:2: C: Surrounding space missing" \
+            ["#{abs('example1.rb')}:3:2: C: Surrounding space missing" \
              ' for operator `=`.',
-             "#{abs('example1.rb')}:2:5: C: Trailing whitespace detected.",
-             "#{abs('example1.rb')}:3:2: C: Trailing whitespace detected.",
+             "#{abs('example1.rb')}:3:5: C: Trailing whitespace detected.",
+             "#{abs('example1.rb')}:4:2: C: Trailing whitespace detected.",
              "#{abs('example2.rb')}:1:1: C: Incorrect indentation detected" \
              ' (column 0 instead of 1).',
-             "#{abs('example2.rb')}:2:1: C: Tab detected.",
-             "#{abs('example2.rb')}:2:2: C: Indentation of first line in " \
+             "#{abs('example2.rb')}:3:1: C: Tab detected.",
+             "#{abs('example2.rb')}:3:2: C: Indentation of first line in " \
              'file detected.',
-             "#{abs('example2.rb')}:3:1: C: Inconsistent indentation " \
+             "#{abs('example2.rb')}:4:1: C: Inconsistent indentation " \
              'detected.',
              ''].join("\n")
           expect($stdout.string).to eq(expected_output)

diff --git a/spec/rubocop/cli_spec.rb b/spec/rubocop/cli_spec.rb
@@ -128,6 +128,7 @@ def interrupt
     context 'when super is used with a block' do
       it 'still returns 0' do
         create_file('example.rb', ['# frozen_string_literal: true',
+                                   '',
                                    '# this is a class',
                                    'class Thing',
                                    '  def super_with_block',
@@ -244,13 +245,15 @@ def interrupt
                                      '  EnforcedStyle: always'])
         expect(cli.run(['--format', 'offenses', '-a', 'example.rb'])).to eq(0)
         expect($stdout.string).to eq(['',
+                                      '1  Style/EmptyLineAfterMagicComment',
                                       '1  Style/FrozenStringLiteralComment',
                                       '--',
-                                      '1  Total',
+                                      '2  Total',
                                       '',
                                       ''].join("\n"))
         expect(IO.read('example.rb'))
           .to eq(['# frozen_string_literal: true',
+                  '',
                   'a = 1 # rubocop:disable Lint/UselessAssignment',
                   ''].join("\n"))
       end

diff --git a/spec/rubocop/cop/rails/http_positional_arguments_spec.rb b/spec/rubocop/cop/rails/http_positional_arguments_spec.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 require 'spec_helper'
 
 describe RuboCop::Cop::Rails::HttpPositionalArguments do

diff --git a/spec/rubocop/cop/rails/request_referer_spec.rb b/spec/rubocop/cop/rails/request_referer_spec.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 require 'spec_helper'
 
 describe RuboCop::Cop::Rails::RequestReferer, :config do

diff --git a/spec/rubocop/cop/rails/safe_navigation_spec.rb b/spec/rubocop/cop/rails/safe_navigation_spec.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 require 'spec_helper'
 
 describe RuboCop::Cop::Rails::SafeNavigation, :config do

diff --git a/spec/rubocop/cop/rails/save_bang_spec.rb b/spec/rubocop/cop/rails/save_bang_spec.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 require 'spec_helper'
 
 describe RuboCop::Cop::Rails::SaveBang do