Reuse LabelsFinder on Banzai::Filter::LabelReferenceFilter

app/finders/issuable_finder.rb

@@ -128,8 +128,7 @@ class IssuableFinder
       @labels = Label.where(title: label_names)
 
       if projects
-        label_ids = LabelsFinder.new(current_user, project_id: projects).execute.select(:id)
-        @labels = @labels.where(labels: { id: label_ids })
+        @labels = LabelsFinder.new(current_user, project_ids: projects, title: label_names).execute
       end
     else
       @labels = Label.none
@@ -277,7 +276,7 @@ class IssuableFinder
         items = items.with_label(label_names, params[:sort])
 
         if projects
-          label_ids = LabelsFinder.new(current_user, project_id: projects).execute.select(:id)
+          label_ids = LabelsFinder.new(current_user, project_ids: projects).execute.select(:id)
           items = items.where(labels: { id: label_ids })
         end
       end

app/finders/labels_finder.rb

@@ -16,8 +16,16 @@ class LabelsFinder < UnionFinder
 
   def label_ids
     label_ids = []
-    label_ids << Label.where(group_id: projects.joins(:namespace).where(namespaces: { type: 'Group' }).select(:namespace_id)).select(:id)
-    label_ids << Label.where(project_id: projects.select(:id)).select(:id)
+
+    if project
+      label_ids << project.group.labels if project.group.present?
+      label_ids << project.labels
+    else
+      label_ids << Label.where(group_id: projects.group_ids)
+      label_ids << Label.where(project_id: projects.select(:id))
+    end
+
+    label_ids
   end
 
   def sort(items)
@@ -37,18 +45,38 @@ class LabelsFinder < UnionFinder
     params[:project_id].presence
   end
 
+  def project_ids
+    params[:project_ids].presence
+  end
+
   def title
     params[:title].presence
   end
 
+  def project
+    return @project if defined?(@project)
+
+    if project_id
+      @project = available_projects.find(project_id) rescue nil
+    else
+      @project = nil
+    end
+
+    @project
+  end
+
   def projects
     return @projects if defined?(@projects)
 
-    @projects = ProjectsFinder.new.execute(current_user)
-    @projects = @projects.joins(:namespace).where(namespaces: { id: group_id, type: 'Group' }) if group_id
-    @projects = @projects.where(id: project_id) if project_id
+    @projects = available_projects
+    @projects = @projects.in_namespace(group_id) if group_id
+    @projects = @projects.where(id: project_ids) if project_ids
     @projects = @projects.reorder(nil)
 
     @projects
   end
+
+  def available_projects
+    @available_projects ||= ProjectsFinder.new.execute(current_user)
+  end
 end

app/models/project.rb

@@ -388,6 +388,10 @@ class Project < ActiveRecord::Base
         Project.count
       end
     end
+
+    def group_ids
+      joins(:namespace).where(namespaces: { type: 'Group' }).pluck(:namespace_id)
+    end
   end
 
   def lfs_enabled?

lib/banzai/filter/label_reference_filter.rb

@@ -39,13 +39,7 @@ module Banzai
       end
 
       def find_labels(project)
-        label_ids = []
-        label_ids << project.group.labels.select(:id) if project.group.present?
-        label_ids << project.labels.select(:id)
-
-        union = Gitlab::SQL::Union.new(label_ids)
-
-        object_class.where("labels.id IN (#{union.to_sql})")
+        LabelsFinder.new(user, project_id: project.id).execute
       end
 
       # Parameters to pass to `Label.find_by` based on the given arguments
@@ -91,6 +85,10 @@ module Banzai
         object.is_a?(ProjectLabel) && object.project == project
       end
 
+      def user
+        context[:current_user] || context[:author]
+      end
+
       def project
         context[:project]
       end