Fix white-space display in Journal diff (#16810)

* Add test for newlines

* Fix html_safe_gsub

app/helpers/application_helper.rb

@@ -180,13 +180,13 @@ def html_hours(text)
 
   def html_safe_gsub(string, *gsub_args, &)
     html_safe = string.html_safe?
-    string.gsub(*gsub_args, &)
+    result = string.gsub(*gsub_args, &)
 
     # We only mark the string as safe if the previous string was already safe
     if html_safe
-      string.html_safe # rubocop:disable Rails/OutputSafety
+      result.html_safe # rubocop:disable Rails/OutputSafety
     else
-      string
+      result
     end
   end
 

spec/controllers/journals_controller_spec.rb

@@ -52,7 +52,7 @@
       let(:params) { { id: work_package.last_journal.id.to_s, field: :description, format: "js" } }
 
       before do
-        work_package.update_attribute :description, "description"
+        work_package.update_attribute :description, "description\nmore changes"
       end
 
       describe "with a user having :view_work_package permission" do
@@ -62,7 +62,11 @@
           expect(response.body.strip).to be_html_eql <<-HTML
             <div class="text-diff">
               <label class="hidden-for-sighted">Begin of the insertion</label>
-              <ins class="diffmod">description</ins>
+              <ins class="diffmod">
+                description
+                <br/>
+                more changes
+              </ins>
               <label class="hidden-for-sighted">End of the insertion</label>
             </div>
           HTML