fix to empty_when lint to ignore warns for 'when' with comments and e…

…mpty lines

lib/rubocop/cop/lint/empty_when.rb

@@ -10,15 +10,11 @@ module Lint
       #   @bad
       #   case foo
       #   when bar then 1
-      #   when baz then # nothing
+      #   when baz
       #   end
       class EmptyWhen < Cop
         MSG = 'Avoid `when` branches without a body.'.freeze
 
-        def investigate(processed_source)
-          @processed_source = processed_source
-        end
-
         def on_case(node)
           _cond_node, *when_nodes, _else_node = *node
 
@@ -27,6 +23,10 @@ def on_case(node)
           end
         end
 
+        def comment_lines
+          @comment_lines ||= processed_source.comments.map{|comment| comment.loc.line}
+        end
+
         private
 
         def check_when(when_node)
@@ -35,8 +35,26 @@ def check_when(when_node)
         end
 
         def empty_when_body?(when_node)
-          node_comment = @processed_source[when_node.loc.first_line]
-          !(when_node.to_a.last || comment_line?(node_comment))
+          !when_node.to_a.last && no_comments?(when_node)
+        end
+
+        def no_comments?(when_node)
+          (comment_lines & line_range_to_next_node(when_node)).empty?
+        end
+
+        def line_range_to_next_node(node)
+          current_node_begin_line = node.loc.expression.begin.line
+          next_node_begin_line = if next_node(node)
+                                    next_node(node).loc.expression.begin.line
+                                 else
+                                    processed_source.lines.length
+                                 end
+          (current_node_begin_line..next_node_begin_line).to_a
+        end
+
+        def next_node(node)
+          return nil unless node.sibling_index > 0
+          node.parent.children[node.sibling_index + 1]
         end
       end
     end

spec/rubocop/cop/lint/empty_when_spec.rb

@@ -47,13 +47,6 @@
                      'when :baz',
                      'end'].join("\n")
 
-    it_behaves_like 'code with offense',
-                    ['case foo',
-                     'when :bar then 1',
-                     'when :baz # nothing',
-                     'else',
-                     'end'].join("\n")
-
     it_behaves_like 'code with offense',
                     ['case foo',
                      'when :bar then 1',
@@ -142,5 +135,15 @@
                      'else',
                      '  3',
                      'end'].join("\n")
+    it_behaves_like 'code without offense',
+                    ['case',
+                     'when :bar',
+                     '  1',
+                     'when :baz',
+                     '',
+                     '  # nothing',
+                     'else',
+                     '  3',
+                     'end'].join("\n")
   end
 end