Fix Style/ClassAndModuleChildren compaction for oneliner children

Signed-off-by: Alexandre Terrasa <alexandre.terrasa@shopify.com>

changelog/fix_style_class_and_module_children.md

@@ -0,0 +1 @@
+* Fix Style/ClassAndModuleChildren compaction for oneliner children. ([@Morriar][])

lib/rubocop/cop/style/class_and_module_children.rb

@@ -117,13 +117,16 @@ def compact_identifier_name(node)
         end
 
         def remove_end(corrector, body)
-          range = range_between(
-            body.loc.end.begin_pos - leading_spaces(body).size,
-            body.loc.end.end_pos + 1
-          )
+          begin_pos = body.loc.end.begin_pos
+          begin_pos -= leading_spaces(body).size unless oneline?(body)
+          range = range_between(begin_pos, body.loc.end.end_pos + 1)
           corrector.remove(range)
         end
 
+        def oneline?(node)
+          node.loc.name.line == node.loc.end.line
+        end
+
         def configured_indentation_width
           config.for_badge(Layout::IndentationWidth.badge).fetch('Width', 2)
         end

spec/rubocop/cop/style/class_and_module_children_spec.rb

@@ -205,6 +205,24 @@ class FooClass::BarClass
       RUBY
     end
 
+    it 'registers a offense for classes with nested oneline children' do
+      expect_offense(<<~RUBY)
+        class FooClass
+              ^^^^^^^^ Use compact module/class definition instead of nested style.
+          class BarClass end
+        end
+        class FooClass
+              ^^^^^^^^ Use compact module/class definition instead of nested style.
+          class BarClass; end
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        class FooClass::BarClass end
+        class FooClass::BarClass; end
+      RUBY
+    end
+
     it 'registers a offense for modules with nested children' do
       expect_offense(<<~RUBY)
         module FooModule
@@ -224,6 +242,24 @@ def method_example
       RUBY
     end
 
+    it 'registers a offense for modules with nested oneline children' do
+      expect_offense(<<~RUBY)
+        module FooModule
+               ^^^^^^^^^ Use compact module/class definition instead of nested style.
+          module BarModule end
+        end
+        module FooModule
+               ^^^^^^^^^ Use compact module/class definition instead of nested style.
+          module BarModule; end
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        module FooModule::BarModule end
+        module FooModule::BarModule; end
+      RUBY
+    end
+
     it 'correctly indents heavily nested children' do
       expect_offense(<<~RUBY)
         module FooModule