udpated a few things based on MR feedback. Also added model spec

app/finders/issuable_finder.rb

@@ -270,8 +270,7 @@ class IssuableFinder
       if filter_by_no_label?
         items = items.without_label
       else
-        items = items.with_label(label_names.flatten)
-
+        items = items.with_label(label_names)
         if projects
           items = items.where(labels: { project_id: projects })
         end
@@ -282,7 +281,7 @@ class IssuableFinder
   end
 
   def label_names
-    params[:label_name].split(',')
+    params[:label_name].is_a?(String) ? params[:label_name].split(',') : params[:label_name]
   end
 
   def current_user_related?

app/helpers/milestones_helper.rb

@@ -32,7 +32,7 @@ module MilestonesHelper
   end
 
   def milestone_issues_by_label_count(milestone, label, state:)
-    milestone.issues.with_label([label.title]).send(state).size
+    milestone.issues.with_label(label.title).send(state).size
   end
 
   def milestone_progress_bar(milestone)

app/models/concerns/issuable.rb

@@ -37,7 +37,6 @@ module Issuable
     scope :closed, -> { with_state(:closed) }
     scope :order_milestone_due_desc, -> { joins(:milestone).reorder('milestones.due_date DESC, milestones.id DESC') }
     scope :order_milestone_due_asc, -> { joins(:milestone).reorder('milestones.due_date ASC, milestones.id ASC') }
-    scope :with_label, ->(title) { joins(:labels).where(labels: { title: title }).group('issues.id').having("count(distinct labels.title) = #{title.count}") }
     scope :without_label, -> { joins("LEFT OUTER JOIN label_links ON label_links.target_type = '#{name}' AND label_links.target_id = #{table_name}.id").where(label_links: { id: nil }) }
 
     scope :join_project, -> { joins(:project) }
@@ -122,6 +121,14 @@ module Issuable
 
       joins(join_clause).group(issuable_table[:id]).reorder("COUNT(notes.id) DESC")
     end
+
+    def with_label(title)
+      if title.is_a?(Array) && title.count > 1
+        joins(:labels).where(labels: { title: title }).group('issues.id').having("count(distinct labels.title) = #{title.count}")
+      else
+        joins(:labels).where(labels: { title: title })
+      end
+    end
   end
 
   def today?

spec/features/issues/filter_by_labels_spec.rb

-# Uncomment once this is merged with multi-filter-labels
-# Changes are related to using AND in label filters instead of OR
-
-# require 'rails_helper'
-#
-# feature 'Issue filtering by Labels', feature: true do
-#   let(:project) { create(:project, :public) }
-#   let!(:user)   { create(:user)}
-#   let!(:label)  { create(:label, project: project) }
-#
-#   before do
-#     ['bug', 'feature', 'enhancement'].each do |title|
-#       create(:label,
-#              project: project,
-#              title: title)
-#     end
-#
-#     issue1 = create(:issue, title: "Bugfix1", project: project)
-#     issue1.labels << project.labels.find_by(title: 'bug')
-#
-#     issue2 = create(:issue, title: "Bugfix2", project: project)
-#     issue2.labels << project.labels.find_by(title: 'bug')
-#     issue2.labels << project.labels.find_by(title: 'enhancement')
-#
-#     issue3 = create(:issue, title: "Feature1", project: project)
-#     issue3.labels << project.labels.find_by(title: 'feature')
-#
-#     project.team << [user, :master]
-#     login_as(user)
-#
-#     visit namespace_project_issues_path(project.namespace, project)
-#   end
-#
-#   context 'filter by label bug', js: true do
-#     before do
-#       page.find('.js-label-select').click
-#       sleep 0.5
-#       execute_script("$('.dropdown-menu-labels li:contains(\"bug\") a').click()")
-#       page.first('.labels-filter .dropdown-title .dropdown-menu-close-icon').click
-#       sleep 2
-#     end
-#
-#     it 'should show issue "Bugfix1" and "Bugfix2" in issues list' do
-#       expect(page).to have_content "Bugfix1"
-#       expect(page).to have_content "Bugfix2"
-#     end
-#
-#     it 'should not show "Feature1" in issues list' do
-#       expect(page).not_to have_content "Feature1"
-#     end
-#
-#     it 'should show label "bug" in filtered-labels' do
-#       expect(find('.filtered-labels')).to have_content "bug"
-#     end
-#
-#     it 'should not show label "feature" and "enhancement" in filtered-labels' do
-#       expect(find('.filtered-labels')).not_to have_content "feature"
-#       expect(find('.filtered-labels')).not_to have_content "enhancement"
-#     end
-#   end
-#
-#   context 'filter by label feature', js: true do
-#     before do
-#       page.find('.js-label-select').click
-#       sleep 0.5
-#       execute_script("$('.dropdown-menu-labels li:contains(\"feature\") a').click()")
-#       page.first('.labels-filter .dropdown-title .dropdown-menu-close-icon').click
-#       sleep 2
-#     end
-#
-#     it 'should show issue "Feature1" in issues list' do
-#       expect(page).to have_content "Feature1"
-#     end
-#
-#     it 'should not show "Bugfix1" and "Bugfix2" in issues list' do
-#       expect(page).not_to have_content "Bugfix2"
-#       expect(page).not_to have_content "Bugfix1"
-#     end
-#
-#     it 'should show label "feature" in filtered-labels' do
-#       expect(find('.filtered-labels')).to have_content "feature"
-#     end
-#
-#     it 'should not show label "bug" and "enhancement" in filtered-labels' do
-#       expect(find('.filtered-labels')).not_to have_content "bug"
-#       expect(find('.filtered-labels')).not_to have_content "enhancement"
-#     end
-#   end
-#
-#   context 'filter by label enhancement', js: true do
-#     before do
-#       page.find('.js-label-select').click
-#       sleep 0.5
-#       execute_script("$('.dropdown-menu-labels li:contains(\"enhancement\") a').click()")
-#       page.first('.labels-filter .dropdown-title .dropdown-menu-close-icon').click
-#       sleep 2
-#     end
-#
-#     it 'should show issue "Bugfix2" in issues list' do
-#       expect(page).to have_content "Bugfix2"
-#     end
-#
-#     it 'should not show "Feature1" and "Bugfix1" in issues list' do
-#       expect(page).not_to have_content "Feature1"
-#       expect(page).not_to have_content "Bugfix1"
-#     end
-#
-#     it 'should show label "enhancement" in filtered-labels' do
-#       expect(find('.filtered-labels')).to have_content "enhancement"
-#     end
-#
-#     it 'should not show label "feature" and "bug" in filtered-labels' do
-#       expect(find('.filtered-labels')).not_to have_content "bug"
-#       expect(find('.filtered-labels')).not_to have_content "feature"
-#     end
-#   end
-#
-#   context 'filter by label enhancement or feature', js: true do
-#     before do
-#       page.find('.js-label-select').click
-#       sleep 0.5
-#       execute_script("$('.dropdown-menu-labels li:contains(\"enhancement\") a').click()")
-#       execute_script("$('.dropdown-menu-labels li:contains(\"feature\") a').click()")
-#       page.first('.labels-filter .dropdown-title .dropdown-menu-close-icon').click
-#       sleep 2
-#     end
-#
-#     it 'should not show "Bugfix1" or "Feature1" in issues list' do
-#       expect(page).not_to have_content "Bugfix1"
-#       expect(page).not_to have_content "Feature1"
-#     end
-#
-#     it 'should show label "enhancement" and "feature" in filtered-labels' do
-#       expect(find('.filtered-labels')).to have_content "enhancement"
-#       expect(find('.filtered-labels')).to have_content "feature"
-#     end
-#
-#     it 'should not show label "bug" in filtered-labels' do
-#       expect(find('.filtered-labels')).not_to have_content "bug"
-#     end
-#   end
-#
-#   context 'filter by label enhancement and bug in issues list', js: true do
-#     before do
-#       page.find('.js-label-select').click
-#       sleep 0.5
-#       execute_script("$('.dropdown-menu-labels li:contains(\"enhancement\") a').click()")
-#       execute_script("$('.dropdown-menu-labels li:contains(\"bug\") a').click()")
-#       page.first('.labels-filter .dropdown-title .dropdown-menu-close-icon').click
-#       sleep 2
-#     end
-#
-#     it 'should show issue "Bugfix2" in issues list' do
-#       expect(page).to have_content "Bugfix2"
-#     end
-#
-#     it 'should not show "Feature1"' do
-#       expect(page).not_to have_content "Feature1"
-#     end
-#
-#     it 'should show label "bug" and "enhancement" in filtered-labels' do
-#       expect(find('.filtered-labels')).to have_content "bug"
-#       expect(find('.filtered-labels')).to have_content "enhancement"
-#     end
-#
-#     it 'should not show label "feature" in filtered-labels' do
-#       expect(find('.filtered-labels')).not_to have_content "feature"
-#     end
-#   end
-# end
+require 'rails_helper'
+
+feature 'Issue filtering by Labels', feature: true do
+  let(:project) { create(:project, :public) }
+  let!(:user)   { create(:user)}
+  let!(:label)  { create(:label, project: project) }
+
+  before do
+    ['bug', 'feature', 'enhancement'].each do |title|
+      create(:label,
+             project: project,
+             title: title)
+    end
+
+    issue1 = create(:issue, title: "Bugfix1", project: project)
+    issue1.labels << project.labels.find_by(title: 'bug')
+
+    issue2 = create(:issue, title: "Bugfix2", project: project)
+    issue2.labels << project.labels.find_by(title: 'bug')
+    issue2.labels << project.labels.find_by(title: 'enhancement')
+
+    issue3 = create(:issue, title: "Feature1", project: project)
+    issue3.labels << project.labels.find_by(title: 'feature')
+
+    project.team << [user, :master]
+    login_as(user)
+
+    visit namespace_project_issues_path(project.namespace, project)
+  end
+
+  context 'filter by label bug', js: true do
+    before do
+      page.find('.js-label-select').click
+      sleep 0.5
+      execute_script("$('.dropdown-menu-labels li:contains(\"bug\") a').click()")
+      page.first('.labels-filter .dropdown-title .dropdown-menu-close-icon').click
+      sleep 2
+    end
+
+    it 'should show issue "Bugfix1" and "Bugfix2" in issues list' do
+      expect(page).to have_content "Bugfix1"
+      expect(page).to have_content "Bugfix2"
+    end
+
+    it 'should not show "Feature1" in issues list' do
+      expect(page).not_to have_content "Feature1"
+    end
+
+    it 'should show label "bug" in filtered-labels' do
+      expect(find('.filtered-labels')).to have_content "bug"
+    end
+
+    it 'should not show label "feature" and "enhancement" in filtered-labels' do
+      expect(find('.filtered-labels')).not_to have_content "feature"
+      expect(find('.filtered-labels')).not_to have_content "enhancement"
+    end
+  end
+
+  context 'filter by label feature', js: true do
+    before do
+      page.find('.js-label-select').click
+      sleep 0.5
+      execute_script("$('.dropdown-menu-labels li:contains(\"feature\") a').click()")
+      page.first('.labels-filter .dropdown-title .dropdown-menu-close-icon').click
+      sleep 2
+    end
+
+    it 'should show issue "Feature1" in issues list' do
+      expect(page).to have_content "Feature1"
+    end
+
+    it 'should not show "Bugfix1" and "Bugfix2" in issues list' do
+      expect(page).not_to have_content "Bugfix2"
+      expect(page).not_to have_content "Bugfix1"
+    end
+
+    it 'should show label "feature" in filtered-labels' do
+      expect(find('.filtered-labels')).to have_content "feature"
+    end
+
+    it 'should not show label "bug" and "enhancement" in filtered-labels' do
+      expect(find('.filtered-labels')).not_to have_content "bug"
+      expect(find('.filtered-labels')).not_to have_content "enhancement"
+    end
+  end
+
+  context 'filter by label enhancement', js: true do
+    before do
+      page.find('.js-label-select').click
+      sleep 0.5
+      execute_script("$('.dropdown-menu-labels li:contains(\"enhancement\") a').click()")
+      page.first('.labels-filter .dropdown-title .dropdown-menu-close-icon').click
+      sleep 2
+    end
+
+    it 'should show issue "Bugfix2" in issues list' do
+      expect(page).to have_content "Bugfix2"
+    end
+
+    it 'should not show "Feature1" and "Bugfix1" in issues list' do
+      expect(page).not_to have_content "Feature1"
+      expect(page).not_to have_content "Bugfix1"
+    end
+
+    it 'should show label "enhancement" in filtered-labels' do
+      expect(find('.filtered-labels')).to have_content "enhancement"
+    end
+
+    it 'should not show label "feature" and "bug" in filtered-labels' do
+      expect(find('.filtered-labels')).not_to have_content "bug"
+      expect(find('.filtered-labels')).not_to have_content "feature"
+    end
+  end
+
+  context 'filter by label enhancement or feature', js: true do
+    before do
+      page.find('.js-label-select').click
+      sleep 0.5
+      execute_script("$('.dropdown-menu-labels li:contains(\"enhancement\") a').click()")
+      execute_script("$('.dropdown-menu-labels li:contains(\"feature\") a').click()")
+      page.first('.labels-filter .dropdown-title .dropdown-menu-close-icon').click
+      sleep 2
+    end
+
+    it 'should not show "Bugfix1" or "Feature1" in issues list' do
+      expect(page).not_to have_content "Bugfix1"
+      expect(page).not_to have_content "Feature1"
+    end
+
+    it 'should show label "enhancement" and "feature" in filtered-labels' do
+      expect(find('.filtered-labels')).to have_content "enhancement"
+      expect(find('.filtered-labels')).to have_content "feature"
+    end
+
+    it 'should not show label "bug" in filtered-labels' do
+      expect(find('.filtered-labels')).not_to have_content "bug"
+    end
+  end
+
+  context 'filter by label enhancement and bug in issues list', js: true do
+    before do
+      page.find('.js-label-select').click
+      sleep 0.5
+      execute_script("$('.dropdown-menu-labels li:contains(\"enhancement\") a').click()")
+      execute_script("$('.dropdown-menu-labels li:contains(\"bug\") a').click()")
+      page.first('.labels-filter .dropdown-title .dropdown-menu-close-icon').click
+      sleep 2
+    end
+
+    it 'should show issue "Bugfix2" in issues list' do
+      expect(page).to have_content "Bugfix2"
+    end
+
+    it 'should not show "Feature1"' do
+      expect(page).not_to have_content "Feature1"
+    end
+
+    it 'should show label "bug" and "enhancement" in filtered-labels' do
+      expect(find('.filtered-labels')).to have_content "bug"
+      expect(find('.filtered-labels')).to have_content "enhancement"
+    end
+
+    it 'should not show label "feature" in filtered-labels' do
+      expect(find('.filtered-labels')).not_to have_content "feature"
+    end
+  end
+end

spec/models/concerns/issuable_spec.rb

@@ -212,4 +212,28 @@ describe Issue, "Issuable" do
       expect(issue.downvotes).to eq(1)
     end
   end
-end
+
+  describe ".with_label" do
+    let(:example_label) { 'test1' }
+    let(:example_labels) { ['test1', 'test2'] }
+
+    it 'finds issue with 1 label' do
+      setup_labels([example_label])
+
+      expect(Issue.with_label(example_label).count).to eq(1)
+    end
+
+    it 'finds issue with 2 labels' do
+      setup_labels(example_labels)
+
+      expect(Issue.with_label(example_labels).to_a.count).to eq(1)
+    end
+
+    def setup_labels(label_names)
+      labels = label_names.map do |label|
+        create(:label, project: issue.project, title: label)
+      end
+      issue.labels << labels
+    end
+  end
+end
\ No newline at end of file