Add test for trailing newline with `render_in` (#1207)

* Add test for trailing newline with render_in

* Update changelog

* Lint

* Add tests directly on ViewComponent::Base

* Lint

Co-authored-by: Joel Hawksley <joelhawksley@github.com>

docs/CHANGELOG.md

@@ -7,6 +7,10 @@ title: Changelog
 
 ## main
 
+* Add a test to ensure trailing newlines are stripped when rendering with `#render_in`.
+
+    *Simon Fish*
+
 * Add WEBrick as a depenency to the docs application.
 
     *Connor McQuillan*

test/sandbox/test/components/previews/display_inline_component_preview.rb

@@ -2,4 +2,6 @@
 
 class DisplayInlineComponentPreview < ViewComponent::Preview
   def with_newline; end
+
+  def with_newline_render_in; end
 end

test/sandbox/test/components/previews/display_inline_component_preview/with_newline_render_in.html.erb

@@ -0,0 +1 @@
+<%= DisplayInlineComponent.new.render_in(controller.view_context) %><%= DisplayInlineComponent.new.render_in(controller.view_context) %>

test/test_helper.rb

@@ -93,14 +93,14 @@ def without_template_annotations
   if ActionView::Base.respond_to?(:annotate_rendered_view_with_filenames)
     old_value = ActionView::Base.annotate_rendered_view_with_filenames
     ActionView::Base.annotate_rendered_view_with_filenames = false
-    app.reloader.reload!
+    app.reloader.reload! if defined?(app)
 
     with_new_cache do
       yield
     end
 
     ActionView::Base.annotate_rendered_view_with_filenames = old_value
-    app.reloader.reload!
+    app.reloader.reload! if defined?(app)
   else
     yield
   end

test/view_component/base_test.rb

@@ -77,4 +77,17 @@ class ViewComponent::Base::UnitTest < Minitest::Test
       TranslatableComponent._sidecar_files(["yml"])
     )
   end
+
+  def test_does_not_render_additional_newline_with_render_in
+    skip unless Rails::VERSION::MAJOR >= 7
+    without_template_annotations do
+      ActionView::Template::Handlers::ERB.strip_trailing_newlines = true
+      rendered_component = Array.new(2) {
+        DisplayInlineComponent.new.render_in(ActionController::Base.new.view_context)
+      }.join
+      assert_includes rendered_component, "<span>Hello, world!</span><span>Hello, world!</span>"
+    end
+  ensure
+    ActionView::Template::Handlers::ERB.strip_trailing_newlines = false if Rails::VERSION::MAJOR >= 7
+  end
 end

test/view_component/integration_test.rb

@@ -477,6 +477,17 @@ class IntegrationTest < ActionDispatch::IntegrationTest
     ActionView::Template::Handlers::ERB.strip_trailing_newlines = false if Rails::VERSION::MAJOR >= 7
   end
 
+  def test_does_not_render_additional_newline_with_render_in
+    skip unless Rails::VERSION::MAJOR >= 7
+    without_template_annotations do
+      ActionView::Template::Handlers::ERB.strip_trailing_newlines = true
+      get "/rails/view_components/display_inline_component/with_newline_render_in"
+      assert_includes response.body, "<span>Hello, world!</span><span>Hello, world!</span>"
+    end
+  ensure
+    ActionView::Template::Handlers::ERB.strip_trailing_newlines = false if Rails::VERSION::MAJOR >= 7
+  end
+
   def test_renders_the_preview_example_with_its_own_template_and_a_layout
     get "/rails/view_components/my_component/inside_banner"
     assert_includes response.body, "ViewComponent - Admin - Test"