Fix bug where labels would be assigned to issues that were moved

If you attempt to move an issue from one project to another and leave
labels blank, LabelsFinder would assign all labels in the new project
to that issue. The issue is that :title is passed along to the Finder,
but since it appears empty no filtering is done. As a result, all
labels in the group are returned. This fix handles that case.

Closes #23668

3 files changed, 11 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 86878e5af6c..1e2150b9ca7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ Please view this file on the master branch, on stable branches it's out of date.
   - Refactor email, use setter method instead AR callbacks for email attribute (Semyon Pupkov)
 
 ## 8.13.1 (unreleased)
+  - Fix bug where labels would be assigned to issues that were moved
   - Fix error in generating labels
   - Fix reply-by-email not working due to queue name mismatch
   - Fixed hidden pipeline graph on commit and MR page !6895
diff --git a/app/finders/labels_finder.rb b/app/finders/labels_finder.rb
index 6ace14a4bb5..2291c64b84d 100644
--- a/app/finders/labels_finder.rb
+++ b/app/finders/labels_finder.rb
@@ -35,6 +35,10 @@ class LabelsFinder < UnionFinder
   end
 
   def with_title(items)
+    # Match no labels if an empty title is supplied to avoid matching all
+    # labels (e.g. when an issue is moved)
+    return Label.none if params[:title] && params[:title].empty?
+
     items = items.where(title: title) if title
     items
   end
diff --git a/spec/finders/labels_finder_spec.rb b/spec/finders/labels_finder_spec.rb
index 27acc464ea2..114399ea3dc 100644
--- a/spec/finders/labels_finder_spec.rb
+++ b/spec/finders/labels_finder_spec.rb
@@ -64,6 +64,12 @@ describe LabelsFinder do
 
         expect(finder.execute).to eq [group_label_2]
       end
+
+      it 'returns no labels if empty titles are supplied' do
+        finder = described_class.new(user, title: [])
+
+        expect(finder.execute).to be_empty
+      end
     end
   end
 end