[Fix rubocop#4420] Ensure Style/EmptyMethod honours indentation whe…

…n auto-correcting

This cop would ignore indentation when auto-correcting compact style
into expanded style, resulting in indentation problems like:

```
class Foo
  def bar
end
end
```

This change fixes that.

CHANGELOG.md

@@ -12,6 +12,7 @@
 * [#4414](https://github.com/bbatsov/rubocop/issues/4414): Handle pseudo-assignments in `for` loops in `Style/ConditionalAssignment`. ([@bbatsov][])
 * [#4419](https://github.com/bbatsov/rubocop/issues/4419): Handle combination `AllCops: DisabledByDefault: true` and `Rails: Enabled: true`. ([@jonas054][])
 * [#4422](https://github.com/bbatsov/rubocop/issues/4422): Fix missing space in message for `Style/MultipleComparison`. ([@timrogers][])
+* [#4420](https://github.com/bbatsov/rubocop/issues/4420): Ensure `Style/EmptyMethod` honours indentation when auto-correcting. ([@drenmi][])
 
 ## 0.49.0 (2017-05-24)
 
@@ -2801,4 +2802,4 @@
 [@gprado]: https://github.com/gprado
 [@yhirano55]: https://github.com/yhirano55
 [@hoshinotsuyoshi]: https://github.com/hoshinotsuyoshi
-[@timrogers]: https://github.com/timrogers
+[@timrogers]: https://github.com/timrogers

lib/rubocop/cop/style/empty_method.rb

@@ -75,9 +75,10 @@ def message
         def corrected(node)
           method_name, args, _body, scope = method_def_node_parts(node)
 
-          arguments = args.source unless args.children.empty?
-          joint = compact_style? ? '; ' : "\n"
-          scope = scope ? 'self.' : ''
+          arguments = !args.children.empty? ? args.source : ''
+          indent    = ' ' * node.loc.column
+          joint     = compact_style? ? '; ' : "\n#{indent}"
+          scope     = scope ? 'self.' : ''
 
           ["def #{scope}#{method_name}#{arguments}", 'end'].join(joint)
         end

spec/rubocop/cop/style/empty_method_spec.rb

@@ -182,5 +182,16 @@
                        '  # bar',
                        'end']
     end
+
+    context 'when method is nested in class scope' do
+      it_behaves_like 'code with offense',
+                      ['class Foo',
+                       '  def bar; end',
+                       'end'].join("\n"),
+                      ['class Foo',
+                       '  def bar',
+                       '  end',
+                       'end'].join("\n")
+    end
   end
 end