Avoid allocating new string when output_postamble is blank (#1911)

* Avoid allocating new string when output_postamble is blank

* Apply suggestions from code review

---------

Co-authored-by: Joel Hawksley <[email protected]>
Co-authored-by: Joel Hawksley <[email protected]>

Author: mitchellhenke

docs/CHANGELOG.md

@@ -30,6 +30,10 @@ nav_order: 5
 
     *Olle Jonsson*
 
+* Avoid duplicating rendered string when `output_postamble` is blank.
+
+    *Mitchell Henke*
+
 ## 3.8.0
 
 * Use correct value for the `config.action_dispatch.show_exceptions` config option for edge Rails.

lib/view_component/base.rb

@@ -104,7 +104,12 @@ def render_in(view_context, &block)
       before_render
 
       if render?
-        render_template_for(@__vc_variant).to_s + output_postamble
+        # Avoid allocating new string when output_postamble is blank
+        if output_postamble.blank?
+          render_template_for(@__vc_variant).to_s
+        else
+          render_template_for(@__vc_variant).to_s + output_postamble
+        end
       else
         ""
       end