Adds Rubocop rule for line break around conditionals

1 files changed, 119 insertions, 0 deletions

diff --git a/rubocop/cop/line_break_around_conditional_block.rb b/rubocop/cop/line_break_around_conditional_block.rb
new file mode 100644
index 00000000000..3e7021e724e
--- /dev/null
+++ b/rubocop/cop/line_break_around_conditional_block.rb
@@ -0,0 +1,119 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    # Ensures a line break around conditional blocks.
+    #
+    # @example
+    #    # bad
+    #    do_something
+    #    if condition
+    #      do_extra_stuff
+    #    end
+    #    do_something_more
+    #
+    #    # good
+    #    do_something
+    #
+    #    if condition
+    #      do_extra_stuff
+    #    end
+    #
+    #    do_something_more
+    #
+    #    # bad
+    #    do_something
+    #    unless condition
+    #      do_extra_stuff
+    #    end
+    #
+    #    do_something_more
+    #
+    #    # good
+    #    def a_method
+    #      if condition
+    #        do_something
+    #      end
+    #    end
+    #
+    #    # good
+    #    on_block do
+    #      if condition
+    #        do_something
+    #      end
+    #    end
+    class LineBreakAroundConditionalBlock < RuboCop::Cop::Cop
+      MSG = 'Add a line break around conditional blocks'
+
+      def on_if(node)
+        return if node.single_line?
+        return unless node.if? || node.unless?
+
+        add_offense(node, location: :expression, message: MSG) unless previous_line_valid?(node)
+        add_offense(node, location: :expression, message: MSG) unless last_line_valid?(node)
+      end
+
+      def autocorrect(node)
+        lambda do |corrector|
+          line = range_by_whole_lines(node.source_range)
+          unless previous_line_valid?(node)
+            corrector.insert_before(line, "\n")
+          end
+
+          unless last_line_valid?(node)
+            corrector.insert_after(line, "\n")
+          end
+        end
+      end
+
+      private
+
+      def previous_line_valid?(node)
+        previous_line(node).empty? ||
+          start_clause_line?(previous_line(node)) ||
+          block_start?(previous_line(node)) ||
+          begin_line?(previous_line(node)) ||
+          assignment_line?(previous_line(node))
+      end
+
+      def last_line_valid?(node)
+        last_line(node).empty? ||
+          end_line?(last_line(node)) ||
+          end_clause_line?(last_line(node))
+      end
+
+      def previous_line(node)
+        processed_source[node.loc.line - 2]
+      end
+
+      def last_line(node)
+        processed_source[node.loc.last_line]
+      end
+
+      def start_clause_line?(line)
+        line =~ /^\s*(def|=end|#|module|class|if|unless|else|elsif|ensure|when)/
+      end
+
+      def end_clause_line?(line)
+        line =~ /^\s*(rescue|else|elsif|when)/
+      end
+
+      def begin_line?(line)
+        # an assignment followed by a begin or ust a begin
+        line =~ /^\s*(@?(\w|\|+|=|\[|\]|\s)+begin|begin)/
+      end
+
+      def assignment_line?(line)
+        line =~ /^\s*.*=/
+      end
+
+      def block_start?(line)
+        line.match(/ (do|{)( \|.*?\|)?\s?$/)
+      end
+
+      def end_line?(line)
+        line =~ /^\s*(end|})/
+      end
+    end
+  end
+end