6 files changed, 48 insertions, 2 deletions

diff --git a/app/helpers/labels_helper.rb b/app/helpers/labels_helper.rb
index 39f661b5f0c..bd53add80ca 100644
--- a/app/helpers/labels_helper.rb
+++ b/app/helpers/labels_helper.rb
@@ -227,6 +227,10 @@ module LabelsHelper
     "#{action} at #{level} level"
   end
 
+  def labels_sorted_by_title(labels)
+    labels.sort_by(&:title)
+  end
+
   # Required for Banzai::Filter::LabelReferenceFilter
   module_function :render_colored_label, :text_color_for_bg, :escape_once
 end
diff --git a/app/views/projects/issues/_issue.html.haml b/app/views/projects/issues/_issue.html.haml
index 31c72f2f759..ce7c7091c93 100644
--- a/app/views/projects/issues/_issue.html.haml
+++ b/app/views/projects/issues/_issue.html.haml
@@ -36,7 +36,7 @@
               = issue.due_date.to_s(:medium)
           - if issue.labels.any?
              
-            - issue.labels.each do |label|
+            - labels_sorted_by_title(issue.labels).each do |label|
               = link_to_label(label, subject: issue.project, css_class: 'label-link')
 
       .issuable-meta
diff --git a/app/views/projects/merge_requests/_merge_request.html.haml b/app/views/projects/merge_requests/_merge_request.html.haml
index ac29cd8f679..90916191d97 100644
--- a/app/views/projects/merge_requests/_merge_request.html.haml
+++ b/app/views/projects/merge_requests/_merge_request.html.haml
@@ -34,7 +34,7 @@
               = merge_request.target_branch
         - if merge_request.labels.any?
            
-          - merge_request.labels.each do |label|
+          - labels_sorted_by_title(merge_request.labels).each do |label|
             = link_to_label(label, subject: merge_request.project, type: :merge_request, css_class: 'label-link')
 
     .issuable-meta
diff --git a/changelogs/unreleased/dz-sort-labels-alphabetically.yml b/changelogs/unreleased/dz-sort-labels-alphabetically.yml
new file mode 100644
index 00000000000..acfde3de999
--- /dev/null
+++ b/changelogs/unreleased/dz-sort-labels-alphabetically.yml
@@ -0,0 +1,5 @@
+---
+title: Sort labels alphabetically on issues and merge requests list
+merge_request: 25470
+author:
+type: changed
diff --git a/spec/features/issuables/issuable_list_spec.rb b/spec/features/issuables/issuable_list_spec.rb
index 2f45ef856a5..7b6e9cd66b2 100644
--- a/spec/features/issuables/issuable_list_spec.rb
+++ b/spec/features/issuables/issuable_list_spec.rb
@@ -28,6 +28,22 @@ describe 'issuable list' do
       expect(first('.fa-thumbs-down').find(:xpath, '..')).to have_content(1)
       expect(first('.fa-comments').find(:xpath, '..')).to have_content(2)
     end
+
+    it 'sorts labels alphabetically' do
+      label1 = create(:label, project: project, title: 'a')
+      label2 = create(:label, project: project, title: 'z')
+      label3 = create(:label, project: project, title: 'X')
+      label4 = create(:label, project: project, title: 'B')
+      issuable = create_issuable(issuable_type)
+      issuable.labels << [label1, label2, label3, label4]
+
+      visit_issuable_list(issuable_type)
+
+      expect(all('.label-link')[0].text).to have_content('B')
+      expect(all('.label-link')[1].text).to have_content('X')
+      expect(all('.label-link')[2].text).to have_content('a')
+      expect(all('.label-link')[3].text).to have_content('z')
+    end
   end
 
   it "counts merge requests closing issues icons for each issue" do
@@ -45,6 +61,14 @@ describe 'issuable list' do
     end
   end
 
+  def create_issuable(issuable_type)
+    if issuable_type == :issue
+      create(:issue, project: project)
+    else
+      create(:merge_request, source_project: project)
+    end
+  end
+
   def create_issuables(issuable_type)
     3.times do |n|
       issuable =
diff --git a/spec/helpers/labels_helper_spec.rb b/spec/helpers/labels_helper_spec.rb
index c04f679bcf0..012678db9c2 100644
--- a/spec/helpers/labels_helper_spec.rb
+++ b/spec/helpers/labels_helper_spec.rb
@@ -236,4 +236,17 @@ describe LabelsHelper do
       expect(labels_filter_path(format: :json)).to eq(dashboard_labels_path(format: :json))
     end
   end
+
+  describe 'labels_sorted_by_title' do
+    it 'sorts labels alphabetically' do
+      label1 = double(:label, title: 'a')
+      label2 = double(:label, title: 'B')
+      label3 = double(:label, title: 'c')
+      label4 = double(:label, title: 'D')
+      labels = [label1, label2, label3, label4]
+
+      expect(labels_sorted_by_title(labels))
+        .to match_array([label2, label4, label1, label3])
+    end
+  end
 end