From 1b54d02dabd56e13abe090993e741dc4337818da Mon Sep 17 00:00:00 2001
From: Alexandru Croitor <acroitor@gitlab.com>
Date: Thu, 23 May 2019 17:16:21 +0300
Subject: Remove deprecated dashboard & group milestone pages

Replaces legacy GroupMilestone, DashboardMilestone, GlobalMilestone
models with Group model.
Replaces dynamic milestones pages with corresponding
project or group milestone pages.
Other code cleanup related to dynamic milestone pages

https://gitlab.com/gitlab-org/gitlab-ce/issues/39545
---
 app/controllers/dashboard/milestones_controller.rb |  30 +--
 app/controllers/groups/milestones_controller.rb    |  61 +-----
 app/controllers/projects/milestones_controller.rb  |   2 +-
 app/finders/milestones_finder.rb                   |   6 +-
 app/helpers/milestones_helper.rb                   |  21 ---
 app/models/concerns/milestoneish.rb                |  16 --
 app/models/dashboard_group_milestone.rb            |  21 ---
 app/models/dashboard_milestone.rb                  |  15 --
 app/models/global_milestone.rb                     | 102 ----------
 app/models/group_milestone.rb                      |  43 -----
 .../dashboard/milestones/_milestone.html.haml      |   1 -
 app/views/dashboard/milestones/show.html.haml      |   5 -
 app/views/groups/milestones/_milestone.html.haml   |   2 -
 app/views/groups/milestones/index.html.haml        |   5 +-
 app/views/groups/milestones/show.html.haml         |   1 -
 app/views/projects/milestones/_milestone.html.haml |   1 -
 app/views/shared/milestones/_milestone.html.haml   |  46 ++---
 app/views/shared/milestones/_tabs.html.haml        |  16 +-
 app/views/shared/milestones/_top.html.haml         |  37 +---
 .../39545-cleanup-dynamic-milestone-pages.yml      |   5 +
 config/routes/dashboard.rb                         |   8 +-
 config/routes/group.rb                             |   8 +-
 .../dashboard/milestones_controller_spec.rb        |  26 +--
 .../groups/milestones_controller_spec.rb           | 120 ++----------
 spec/features/dashboard/milestone_tabs_spec.rb     |  40 ----
 spec/features/groups/milestone_spec.rb             |  35 ++--
 spec/features/groups/milestones_sorting_spec.rb    |  17 +-
 spec/features/milestone_spec.rb                    |  14 --
 spec/models/global_milestone_spec.rb               | 207 ---------------------
 spec/models/group_milestone_spec.rb                |  57 ------
 .../shared_examples/milestone_tabs_examples.rb     |  10 +-
 spec/views/shared/milestones/_top.html.haml.rb     |  16 --
 32 files changed, 98 insertions(+), 896 deletions(-)
 delete mode 100644 app/models/dashboard_group_milestone.rb
 delete mode 100644 app/models/dashboard_milestone.rb
 delete mode 100644 app/models/global_milestone.rb
 delete mode 100644 app/models/group_milestone.rb
 delete mode 100644 app/views/dashboard/milestones/show.html.haml
 create mode 100644 changelogs/unreleased/39545-cleanup-dynamic-milestone-pages.yml
 delete mode 100644 spec/features/dashboard/milestone_tabs_spec.rb
 delete mode 100644 spec/models/global_milestone_spec.rb
 delete mode 100644 spec/models/group_milestone_spec.rb

diff --git a/app/controllers/dashboard/milestones_controller.rb b/app/controllers/dashboard/milestones_controller.rb
index 912036da0ea..d2606fcde35 100644
--- a/app/controllers/dashboard/milestones_controller.rb
+++ b/app/controllers/dashboard/milestones_controller.rb
@@ -1,48 +1,32 @@
 # frozen_string_literal: true
 
 class Dashboard::MilestonesController < Dashboard::ApplicationController
-  include MilestoneActions
-
   before_action :projects
   before_action :groups, only: :index
-  before_action :milestone, only: [:show, :merge_requests, :participants, :labels]
 
   def index
     respond_to do |format|
       format.html do
         @milestone_states = Milestone.states_count(@projects.select(:id), @groups.select(:id))
-        @milestones = Kaminari.paginate_array(milestones).page(params[:page])
+        @milestones = milestones.page(params[:page])
       end
       format.json do
-        render json: milestones
+        render json: milestones.to_json(only: [:id, :title], methods: :name)
       end
     end
   end
 
-  def show
-  end
-
   private
 
-  def group_milestones
-    DashboardGroupMilestone.build_collection(groups, params)
-  end
-
-  # See [#39545](https://gitlab.com/gitlab-org/gitlab-ce/issues/39545) for info about the deprecation of dynamic milestones
-  def dynamic_milestones
-    DashboardMilestone.build_collection(@projects, params)
-  end
-
   def milestones
-    @milestones = group_milestones + dynamic_milestones
-  end
-
-  def milestone
-    @milestone = DashboardMilestone.build(@projects, params[:title])
-    render_404 unless @milestone
+    MilestonesFinder.new(search_params).execute
   end
 
   def groups
     @groups ||= GroupsFinder.new(current_user, all_available: false).execute
   end
+
+  def search_params
+    params.permit(:state, :search_title).merge(group_ids: groups.map(&:id), project_ids: projects)
+  end
 end
diff --git a/app/controllers/groups/milestones_controller.rb b/app/controllers/groups/milestones_controller.rb
index 7ed4384089b..3c8a99131d4 100644
--- a/app/controllers/groups/milestones_controller.rb
+++ b/app/controllers/groups/milestones_controller.rb
@@ -1,20 +1,18 @@
 # frozen_string_literal: true
 
 class Groups::MilestonesController < Groups::ApplicationController
-  include MilestoneActions
-
   before_action :group_projects
-  before_action :milestone, only: [:edit, :show, :update, :merge_requests, :participants, :labels, :destroy]
+  before_action :milestone, only: [:edit, :show, :update, :destroy]
   before_action :authorize_admin_milestones!, only: [:edit, :new, :create, :update, :destroy]
 
   def index
     respond_to do |format|
       format.html do
         @milestone_states = Milestone.states_count(group_projects, [group])
-        @milestones = Kaminari.paginate_array(milestones).page(params[:page])
+        @milestones = milestones.page(params[:page])
       end
       format.json do
-        render json: milestones.map { |m| m.for_display.slice(:id, :title, :name) }
+        render json: milestones.to_json(only: [:id, :title], methods: :name)
       end
     end
   end
@@ -27,7 +25,7 @@ class Groups::MilestonesController < Groups::ApplicationController
     @milestone = Milestones::CreateService.new(group, current_user, milestone_params).execute
 
     if @milestone.persisted?
-      redirect_to milestone_path
+      redirect_to milestone_path(@milestone)
     else
       render "new"
     end
@@ -37,23 +35,15 @@ class Groups::MilestonesController < Groups::ApplicationController
   end
 
   def edit
-    render_404 if @milestone.legacy_group_milestone?
   end
 
   def update
-    # Keep this compatible with legacy group milestones where we have to update
-    # all projects milestones states at once.
-    milestones, update_params = get_milestones_for_update
-    milestones.each do |milestone|
-      Milestones::UpdateService.new(milestone.parent, current_user, update_params).execute(milestone)
-    end
+    Milestones::UpdateService.new(@milestone.parent, current_user, milestone_params).execute(@milestone)
 
-    redirect_to milestone_path
+    redirect_to milestone_path(@milestone)
   end
 
   def destroy
-    return render_404 if @milestone.legacy_group_milestone?
-
     Milestones::DestroyService.new(group, current_user).execute(@milestone)
 
     respond_to do |format|
@@ -64,14 +54,6 @@ class Groups::MilestonesController < Groups::ApplicationController
 
   private
 
-  def get_milestones_for_update
-    if @milestone.legacy_group_milestone?
-      [@milestone.milestones, legacy_milestone_params]
-    else
-      [[@milestone], milestone_params]
-    end
-  end
-
   def authorize_admin_milestones!
     return render_404 unless can?(current_user, :admin_milestone, group)
   end
@@ -80,41 +62,18 @@ class Groups::MilestonesController < Groups::ApplicationController
     params.require(:milestone).permit(:title, :description, :start_date, :due_date, :state_event)
   end
 
-  def legacy_milestone_params
-    params.require(:milestone).permit(:state_event)
-  end
-
-  def milestone_path
-    if @milestone.legacy_group_milestone?
-      group_milestone_path(group, @milestone.safe_title, title: @milestone.title)
-    else
-      group_milestone_path(group, @milestone.iid)
-    end
-  end
-
   def milestones
-    milestones = MilestonesFinder.new(search_params).execute
-
-    @sort = params[:sort] || 'due_date_asc'
-    MilestoneArray.sort(milestones + legacy_milestones, @sort)
-  end
-
-  def legacy_milestones
-    GroupMilestone.build_collection(group, group_projects, params)
+    MilestonesFinder.new(search_params).execute
   end
 
   def milestone
-    @milestone =
-      if params[:title]
-        GroupMilestone.build(group, group_projects, params[:title])
-      else
-        group.milestones.find_by_iid(params[:id])
-      end
+    @milestone = group.milestones.find_by_iid(params[:id])
 
     render_404 unless @milestone
   end
 
   def search_params
-    params.permit(:state, :search_title).merge(group_ids: group.id)
+    @sort = params[:sort] || 'due_date_asc'
+    params.permit(:state, :search_title).merge(sort: @sort, group_ids: group.id, project_ids: group_projects)
   end
 end
diff --git a/app/controllers/projects/milestones_controller.rb b/app/controllers/projects/milestones_controller.rb
index f6f61b6e5fb..06bcedb5e3a 100644
--- a/app/controllers/projects/milestones_controller.rb
+++ b/app/controllers/projects/milestones_controller.rb
@@ -32,7 +32,7 @@ class Projects::MilestonesController < Projects::ApplicationController
         @milestones = @milestones.page(params[:page])
       end
       format.json do
-        render json: @milestones.to_json(methods: :name)
+        render json: @milestones.to_json(only: [:id, :title], methods: :name)
       end
     end
   end
diff --git a/app/finders/milestones_finder.rb b/app/finders/milestones_finder.rb
index 77b55cbb838..441d4d16978 100644
--- a/app/finders/milestones_finder.rb
+++ b/app/finders/milestones_finder.rb
@@ -56,10 +56,8 @@ class MilestonesFinder
     Milestone.filter_by_state(items, params[:state])
   end
 
-  # rubocop: disable CodeReuse/ActiveRecord
   def order(items)
-    order_statement = Gitlab::Database.nulls_last_order('due_date', 'ASC')
-    items.reorder(order_statement).order('title ASC')
+    sort_by = params[:sort].presence || 'due_date_asc'
+    items.sort_by_attribute(sort_by).order('title ASC') # rubocop: disable CodeReuse/ActiveRecord
   end
-  # rubocop: enable CodeReuse/ActiveRecord
 end
diff --git a/app/helpers/milestones_helper.rb b/app/helpers/milestones_helper.rb
index c1a04640688..017efd68e06 100644
--- a/app/helpers/milestones_helper.rb
+++ b/app/helpers/milestones_helper.rb
@@ -226,27 +226,6 @@ module MilestonesHelper
     end
   end
 
-  def group_milestone_route(milestone, params = {})
-    params = nil if params.empty?
-
-    if milestone.legacy_group_milestone?
-      group_milestone_path(@group, milestone.safe_title, title: milestone.title, milestone: params)
-    else
-      group_milestone_path(@group, milestone.iid, milestone: params)
-    end
-  end
-
-  def group_or_project_milestone_path(milestone)
-    params =
-      if milestone.group_milestone?
-        { milestone: { title: milestone.title } }
-      else
-        { title: milestone.title }
-      end
-
-    milestone_path(milestone.milestone, params)
-  end
-
   def can_admin_project_milestones?
     strong_memoize(:can_admin_project_milestones) do
       can?(current_user, :admin_milestone, @project)
diff --git a/app/models/concerns/milestoneish.rb b/app/models/concerns/milestoneish.rb
index 3deb86da6cf..743cdbed04d 100644
--- a/app/models/concerns/milestoneish.rb
+++ b/app/models/concerns/milestoneish.rb
@@ -83,22 +83,6 @@ module Milestoneish
     due_date && due_date.past?
   end
 
-  def group_milestone?
-    false
-  end
-
-  def project_milestone?
-    false
-  end
-
-  def legacy_group_milestone?
-    false
-  end
-
-  def dashboard_milestone?
-    false
-  end
-
   def total_issue_time_spent
     @total_issue_time_spent ||= issues.joins(:timelogs).sum(:time_spent)
   end
diff --git a/app/models/dashboard_group_milestone.rb b/app/models/dashboard_group_milestone.rb
deleted file mode 100644
index ec52f1ed370..00000000000
--- a/app/models/dashboard_group_milestone.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-# frozen_string_literal: true
-# Dashboard Group Milestones are milestones that allow us to pull more info out for the UI that the Milestone object doesn't allow for
-class DashboardGroupMilestone < GlobalMilestone
-  extend ::Gitlab::Utils::Override
-
-  attr_reader :group_name
-
-  def initialize(milestone)
-    super
-
-    @group_name = milestone.group.full_name
-  end
-
-  def self.build_collection(groups, params)
-    milestones = Milestone.of_groups(groups.select(:id))
-             .reorder_by_due_date_asc
-             .order_by_name_asc
-    milestones = milestones.search_title(params[:search_title]) if params[:search_title].present?
-    Milestone.filter_by_state(milestones, params[:state]).map { |m| new(m) }
-  end
-end
diff --git a/app/models/dashboard_milestone.rb b/app/models/dashboard_milestone.rb
deleted file mode 100644
index 9b377b70e5b..00000000000
--- a/app/models/dashboard_milestone.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-# frozen_string_literal: true
-
-class DashboardMilestone < GlobalMilestone
-  attr_reader :project_name
-
-  def initialize(milestone)
-    super
-
-    @project_name = milestone.project.full_name
-  end
-
-  def project_milestone?
-    true
-  end
-end
diff --git a/app/models/global_milestone.rb b/app/models/global_milestone.rb
deleted file mode 100644
index 59f5a7703e2..00000000000
--- a/app/models/global_milestone.rb
+++ /dev/null
@@ -1,102 +0,0 @@
-# frozen_string_literal: true
-# Global Milestones are milestones that can be shared across multiple projects
-class GlobalMilestone
-  include Milestoneish
-
-  STATE_COUNT_HASH = { opened: 0, closed: 0, all: 0 }.freeze
-
-  attr_reader :milestone
-  alias_attribute :name, :title
-
-  delegate :title, :state, :due_date, :start_date, :participants, :project,
-           :group, :expires_at, :closed?, :iid, :group_milestone?, :safe_title,
-           :milestoneish_id, :parent, to: :milestone
-
-  def to_hash
-    {
-       name: title,
-       title: title,
-       group_name: group&.full_name,
-       project_name: project&.full_name
-    }
-  end
-
-  def for_display
-    @milestone
-  end
-
-  def self.build_collection(projects, params)
-    items = Milestone.of_projects(projects)
-                .reorder_by_due_date_asc
-                .order_by_name_asc
-    items = items.search_title(params[:search_title]) if params[:search_title].present?
-
-    Milestone.filter_by_state(items, params[:state]).map { |m| new(m) }
-  end
-
-  # necessary for legacy milestones
-  def self.build(projects, title)
-    milestones = Milestone.of_projects(projects).where(title: title)
-    return if milestones.blank?
-
-    new(milestones.first)
-  end
-
-  def self.states_count(projects, group = nil)
-    legacy_group_milestones_count = legacy_group_milestone_states_count(projects)
-    group_milestones_count = group_milestones_states_count(group)
-
-    legacy_group_milestones_count.merge(group_milestones_count) do |k, legacy_group_milestones_count, group_milestones_count|
-      legacy_group_milestones_count + group_milestones_count
-    end
-  end
-
-  def self.group_milestones_states_count(group)
-    return STATE_COUNT_HASH unless group
-
-    counts_by_state = Milestone.of_groups(group).count_by_state
-
-    {
-      opened: counts_by_state['active'] || 0,
-      closed: counts_by_state['closed'] || 0,
-      all: counts_by_state.values.sum
-    }
-  end
-
-  def self.legacy_group_milestone_states_count(projects)
-    return STATE_COUNT_HASH unless projects
-
-    # We need to reorder(nil) on the projects, because the controller passes them in sorted.
-    relation = Milestone.of_projects(projects.reorder(nil)).count_by_state
-
-    {
-      opened: relation['active'] || 0,
-      closed: relation['closed'] || 0,
-      all: relation.values.sum
-    }
-  end
-
-  def initialize(milestone)
-    @milestone = milestone
-  end
-
-  def active?
-    state == 'active'
-  end
-
-  def closed?
-    state == 'closed'
-  end
-
-  def issues
-    @issues ||= Issue.of_milestones(milestone).includes(:project, :assignees, :labels)
-  end
-
-  def merge_requests
-    @merge_requests ||= MergeRequest.of_milestones(milestone).includes(:target_project, :assignee, :labels)
-  end
-
-  def labels
-    @labels ||= GlobalLabel.build_collection(milestone.labels).sort_by!(&:title)
-  end
-end
diff --git a/app/models/group_milestone.rb b/app/models/group_milestone.rb
deleted file mode 100644
index 97cb26c6ea9..00000000000
--- a/app/models/group_milestone.rb
+++ /dev/null
@@ -1,43 +0,0 @@
-# frozen_string_literal: true
-# Group Milestones are milestones that can be shared among many projects within the same group
-class GroupMilestone < GlobalMilestone
-  attr_reader :group, :milestones
-
-  def self.build_collection(group, projects, params)
-    params =
-      { state: params[:state], search_title: params[:search_title] }
-
-    project_milestones = Milestone.of_projects(projects)
-    project_milestones = project_milestones.search_title(params[:search_title]) if params[:search_title].present?
-    child_milestones = Milestone.filter_by_state(project_milestones, params[:state])
-    grouped_milestones = child_milestones.group_by(&:title)
-
-    grouped_milestones.map do |title, grouped|
-      new(title, grouped, group)
-    end
-  end
-
-  def self.build(group, projects, title)
-    child_milestones = Milestone.of_projects(projects).where(title: title)
-    return if child_milestones.blank?
-
-    new(title, child_milestones, group)
-  end
-
-  def initialize(title, milestones, group)
-    @milestones = milestones
-    @group = group
-  end
-
-  def milestone
-    @milestone ||= milestones.find { |m| m.description.present? } || milestones.first
-  end
-
-  def issues_finder_params
-    { group_id: group.id }
-  end
-
-  def legacy_group_milestone?
-    true
-  end
-end
diff --git a/app/views/dashboard/milestones/_milestone.html.haml b/app/views/dashboard/milestones/_milestone.html.haml
index 89212eb6bf9..4921de32f65 100644
--- a/app/views/dashboard/milestones/_milestone.html.haml
+++ b/app/views/dashboard/milestones/_milestone.html.haml
@@ -1,5 +1,4 @@
 = render 'shared/milestones/milestone',
-          milestone_path: group_or_project_milestone_path(milestone),
           issues_path: issues_dashboard_path(milestone_title: milestone.title),
           merge_requests_path: merge_requests_dashboard_path(milestone_title: milestone.title),
           milestone: milestone,
diff --git a/app/views/dashboard/milestones/show.html.haml b/app/views/dashboard/milestones/show.html.haml
deleted file mode 100644
index 2129920afd2..00000000000
--- a/app/views/dashboard/milestones/show.html.haml
+++ /dev/null
@@ -1,5 +0,0 @@
-- header_title "Milestones", dashboard_milestones_path
-
-= render 'shared/milestones/top', milestone: @milestone
-= render 'shared/milestones/tabs', milestone: @milestone, show_full_project_name: true
-= render 'shared/milestones/sidebar', milestone: @milestone, affix_offset: 51
diff --git a/app/views/groups/milestones/_milestone.html.haml b/app/views/groups/milestones/_milestone.html.haml
index bae8997e24c..b73626dab81 100644
--- a/app/views/groups/milestones/_milestone.html.haml
+++ b/app/views/groups/milestones/_milestone.html.haml
@@ -1,6 +1,4 @@
-
 = render 'shared/milestones/milestone',
-          milestone_path: group_milestone_route(milestone),
           issues_path: issues_group_path(@group, milestone_title: milestone.title),
           merge_requests_path: merge_requests_group_path(@group, milestone_title: milestone.title),
           milestone: milestone
diff --git a/app/views/groups/milestones/index.html.haml b/app/views/groups/milestones/index.html.haml
index b6fb908c8f6..6fbfdc6ce0f 100644
--- a/app/views/groups/milestones/index.html.haml
+++ b/app/views/groups/milestones/index.html.haml
@@ -16,5 +16,8 @@
         .nothing-here-block No milestones to show
     - else
       - @milestones.each do |milestone|
-        = render 'milestone', milestone: milestone
+        - if milestone.project
+          = render 'projects/milestones/milestone', milestone: milestone
+        - else
+          = render 'milestone', milestone: milestone
   = paginate @milestones, theme: "gitlab"
diff --git a/app/views/groups/milestones/show.html.haml b/app/views/groups/milestones/show.html.haml
index 23b1a22240f..8711f8583de 100644
--- a/app/views/groups/milestones/show.html.haml
+++ b/app/views/groups/milestones/show.html.haml
@@ -1,4 +1,3 @@
 = render "header_title"
 = render 'shared/milestones/top', milestone: @milestone, group: @group
-= render 'shared/milestones/tabs', milestone: @milestone, show_project_name: true if @milestone.legacy_group_milestone?
 = render 'shared/milestones/sidebar', milestone: @milestone, affix_offset: 102
diff --git a/app/views/projects/milestones/_milestone.html.haml b/app/views/projects/milestones/_milestone.html.haml
index bc82b45f902..00937c5bf73 100644
--- a/app/views/projects/milestones/_milestone.html.haml
+++ b/app/views/projects/milestones/_milestone.html.haml
@@ -1,5 +1,4 @@
 = render 'shared/milestones/milestone',
-          milestone_path: project_milestone_path(milestone.project, milestone),
           issues_path: project_issues_path(milestone.project, milestone_title: milestone.title),
           merge_requests_path: project_merge_requests_path(milestone.project, milestone_title: milestone.title),
           milestone: milestone
diff --git a/app/views/shared/milestones/_milestone.html.haml b/app/views/shared/milestones/_milestone.html.haml
index e99aa3f1ee4..e5521f3a3a4 100644
--- a/app/views/shared/milestones/_milestone.html.haml
+++ b/app/views/shared/milestones/_milestone.html.haml
@@ -6,27 +6,21 @@
   .row
     .col-sm-6
       .append-bottom-5
-        %strong= link_to truncate(milestone.title, length: 100), milestone_path
+        %strong= link_to truncate(milestone.title, length: 100), milestone_path(milestone)
         - if @group
           = " - #{milestone_type}"
 
-      - if @project || milestone.is_a?(GlobalMilestone) || milestone.group_milestone?
-        - if milestone.due_date || milestone.start_date
-          .milestone-range.append-bottom-5
-            = milestone_date_range(milestone)
-        %div
-          = render('shared/milestone_expired', milestone: milestone)
-          - if milestone.group_milestone?
-            .label-badge.label-badge-blue.d-inline-block
-              = milestone.group.full_name
-          - if milestone.legacy_group_milestone?
-            .projects
-              - link_to milestone_path(milestone.milestone) do
-                %span.label-badge.label-badge-blue.d-inline-block.append-bottom-5
-                  = dashboard ? milestone.project.full_name : milestone.project.name
-          - if milestone.project
-            .label-badge.label-badge-gray.d-inline-block
-              = milestone.project.full_name
+      - if milestone.due_date || milestone.start_date
+        .milestone-range.append-bottom-5
+          = milestone_date_range(milestone)
+      %div
+        = render('shared/milestone_expired', milestone: milestone)
+        - if milestone.group_milestone?
+          .label-badge.label-badge-blue.d-inline-block
+            = milestone.group.full_name
+        - if milestone.project
+          .label-badge.label-badge-gray.d-inline-block
+            = milestone.project.full_name
 
     .col-sm-4.milestone-progress
       = milestone_progress_bar(milestone)
@@ -49,16 +43,12 @@
                         container: 'body',
                         toggle: 'modal' } }
                 = sprite_icon('level-up', size: 14)
-
-            = link_to 'Close Milestone', project_milestone_path(@project, milestone, milestone: {state_event: :close }), method: :put, remote: true, class: "btn btn-sm btn-close btn-grouped"
-          - unless milestone.active?
-            = link_to 'Reopen Milestone', project_milestone_path(@project, milestone, milestone: {state_event: :activate }), method: :put, class: "btn btn-grouped btn-reopen"
-        - if @group
-          - if can?(current_user, :admin_milestone, @group)
-            - if milestone.closed?
-              = link_to 'Reopen Milestone', group_milestone_route(milestone, {state_event: :activate }), method: :put, class: "btn btn-sm btn-grouped btn-reopen"
-            - else
-              = link_to 'Close Milestone', group_milestone_route(milestone, {state_event: :close }), method: :put, class: "btn btn-sm btn-grouped btn-close"
         - if dashboard
           .label-badge.label-badge-gray
             = milestone_type
+        - else
+          - if can?(current_user, :admin_milestone, milestone.parent)
+            - if milestone.closed?
+              = link_to 'Reopen Milestone', milestone_path(milestone, milestone: {state_event: :activate }), method: :put, class: "btn btn-sm btn-grouped btn-reopen"
+            - else
+              = link_to 'Close Milestone', milestone_path(milestone, milestone: {state_event: :close }), method: :put, class: "btn btn-sm btn-grouped btn-close"
diff --git a/app/views/shared/milestones/_tabs.html.haml b/app/views/shared/milestones/_tabs.html.haml
index b877f66c71e..8db34da10fb 100644
--- a/app/views/shared/milestones/_tabs.html.haml
+++ b/app/views/shared/milestones/_tabs.html.haml
@@ -1,4 +1,5 @@
-- issues_accessible = milestone.is_a?(GlobalMilestone) || can?(current_user, :read_issue, @project)
+- issues_accessible = can?(current_user, :read_issue, @project)
+- mr_active_css_class = 'active' unless issues_accessible
 
 .scrolling-tabs-container.inner-page-scroll-tabs.is-smaller
   .fade-left= icon('angle-left')
@@ -9,15 +10,10 @@
         = link_to '#tab-issues', class: 'nav-link active', 'data-toggle' => 'tab', 'data-show' => '.tab-issues-buttons' do
           Issues
           %span.badge.badge-pill= milestone.issues_visible_to_user(current_user).size
-      %li.nav-item
-        = link_to '#tab-merge-requests', class: 'nav-link', 'data-toggle' => 'tab', 'data-endpoint': milestone_merge_request_tab_path(milestone) do
-          Merge Requests
-          %span.badge.badge-pill= milestone.merge_requests_visible_to_user(current_user).size
-    - else
-      %li.nav-item
-        = link_to '#tab-merge-requests', class: 'nav-link active', 'data-toggle' => 'tab', 'data-endpoint': milestone_merge_request_tab_path(milestone) do
-          Merge Requests
-          %span.badge.badge-pill= milestone.merge_requests.size
+    %li.nav-item
+      = link_to '#tab-merge-requests', class: "nav-link #{mr_active_css_class}", 'data-toggle' => 'tab', 'data-endpoint': milestone_merge_request_tab_path(milestone) do
+        Merge Requests
+        %span.badge.badge-pill= milestone.merge_requests.size
     %li.nav-item
       = link_to '#tab-participants', class: 'nav-link', 'data-toggle' => 'tab', 'data-endpoint': milestone_participants_tab_path(milestone) do
         Participants
diff --git a/app/views/shared/milestones/_top.html.haml b/app/views/shared/milestones/_top.html.haml
index 43503e1d08a..cbb2c6c0656 100644
--- a/app/views/shared/milestones/_top.html.haml
+++ b/app/views/shared/milestones/_top.html.haml
@@ -1,8 +1,7 @@
 - page_title milestone.title
-- @breadcrumb_link = dashboard_milestone_path(milestone.safe_title, title: milestone.title)
+- @breadcrumb_link = milestone_path(milestone)
 
 - group = local_assigns[:group]
-- is_dynamic_milestone = milestone.legacy_group_milestone? || milestone.dashboard_milestone?
 
 .detail-page-header.milestone-page-header
   .status-box{ class: "status-box-#{milestone.closed? ? 'closed' : 'open'}" }
@@ -28,18 +27,14 @@
           = link_to edit_group_milestone_path(group, milestone), class: "btn btn btn-grouped" do
             Edit
         - if milestone.active?
-          = link_to 'Close Milestone', group_milestone_route(milestone, {state_event: :close }), method: :put, class: "btn btn-grouped btn-close"
+          = link_to 'Close Milestone', milestone_path(milestone, milestone: {state_event: :close }), method: :put, class: "btn btn-grouped btn-close"
         - else
-          = link_to 'Reopen Milestone', group_milestone_route(milestone, {state_event: :activate }), method: :put, class: "btn btn-grouped btn-reopen"
-
-        - unless is_dynamic_milestone
-          = render 'shared/milestones/delete_button'
+          = link_to 'Reopen Milestone', milestone_path(milestone, milestone: {state_event: :activate }), method: :put, class: "btn btn-grouped btn-reopen"
+        = render 'shared/milestones/delete_button'
 
     %a.btn.btn-default.btn-grouped.float-right.d-block.d-sm-none.js-sidebar-toggle{ href: "#" }
       = icon('angle-double-left')
 
-= render 'shared/milestones/deprecation_message' if is_dynamic_milestone
-
 .detail-page-description.milestone-detail
   %h2.title
     = markdown_field(milestone, :title)
@@ -55,29 +50,7 @@
 
 = render_if_exists 'shared/milestones/burndown', milestone: @milestone, project: @project
 
-- if is_dynamic_milestone
-  .table-holder
-    %table.table
-      %thead
-        %tr
-          %th Project
-          %th Open issues
-          %th State
-          %th Due date
-        %tr
-          %td
-            - project_name = group ? milestone.project.name : milestone.project.full_name
-            = link_to project_name, milestone_path(milestone.milestone)
-          %td
-            = milestone.milestone.issues_visible_to_user(current_user).opened.count
-          %td
-            - if milestone.closed?
-              Closed
-            - else
-              Open
-          %td
-            = milestone.expires_at
-- elsif milestone.group_milestone?
+- if milestone.group_milestone?
   %br
   View
   = link_to 'Issues', issues_group_path(@group, milestone_title: milestone.title)
diff --git a/changelogs/unreleased/39545-cleanup-dynamic-milestone-pages.yml b/changelogs/unreleased/39545-cleanup-dynamic-milestone-pages.yml
new file mode 100644
index 00000000000..ba00d69cecf
--- /dev/null
+++ b/changelogs/unreleased/39545-cleanup-dynamic-milestone-pages.yml
@@ -0,0 +1,5 @@
+---
+title: Remove deprecated dashboard & group milestone pages
+merge_request: 28668
+author:
+type: removed
diff --git a/config/routes/dashboard.rb b/config/routes/dashboard.rb
index f1e8c2b9d82..7e29a36f020 100644
--- a/config/routes/dashboard.rb
+++ b/config/routes/dashboard.rb
@@ -5,13 +5,7 @@ resource :dashboard, controller: 'dashboard', only: [] do
   get :activity
 
   scope module: :dashboard do
-    resources :milestones, only: [:index, :show] do
-      member do
-        get :merge_requests
-        get :participants
-        get :labels
-      end
-    end
+    resources :milestones, only: [:index]
     resources :labels, only: [:index]
 
     resources :groups, only: [:index]
diff --git a/config/routes/group.rb b/config/routes/group.rb
index 2cf9eb82447..6550bd991ee 100644
--- a/config/routes/group.rb
+++ b/config/routes/group.rb
@@ -45,13 +45,7 @@ constraints(::Constraints::GroupUrlConstrainer.new) do
       post :toggle_subscription, on: :member
     end
 
-    resources :milestones, constraints: { id: %r{[^/]+} } do
-      member do
-        get :merge_requests
-        get :participants
-        get :labels
-      end
-    end
+    resources :milestones, constraints: { id: %r{[^/]+} }
 
     resource :avatar, only: [:destroy]
 
diff --git a/spec/controllers/dashboard/milestones_controller_spec.rb b/spec/controllers/dashboard/milestones_controller_spec.rb
index 67939aa4e6a..5a5ff835549 100644
--- a/spec/controllers/dashboard/milestones_controller_spec.rb
+++ b/spec/controllers/dashboard/milestones_controller_spec.rb
@@ -8,12 +8,7 @@ describe Dashboard::MilestonesController do
   let(:user) { create(:user) }
   let(:project_milestone) { create(:milestone, project: project) }
   let(:group_milestone) { create(:milestone, group: group) }
-  let(:milestone) do
-    DashboardMilestone.build(
-      [project],
-      project_milestone.title
-    )
-  end
+  let(:milestone) { create(:milestone, group: group) }
   let(:issue) { create(:issue, project: project, milestone: project_milestone) }
   let(:group_issue) { create(:issue, milestone: group_milestone, project: create(:project, group: group)) }
 
@@ -28,22 +23,6 @@ describe Dashboard::MilestonesController do
     group.add_developer(user)
   end
 
-  it_behaves_like 'milestone tabs'
-
-  describe "#show" do
-    render_views
-
-    def view_milestone
-      get :show, params: { id: milestone.safe_title, title: milestone.title }
-    end
-
-    it 'shows milestone page' do
-      view_milestone
-
-      expect(response).to have_gitlab_http_status(200)
-    end
-  end
-
   describe "#index" do
     let(:public_group) { create(:group, :public) }
     let!(:public_milestone) { create(:milestone, group: public_group) }
@@ -57,8 +36,7 @@ describe Dashboard::MilestonesController do
 
       expect(response).to have_gitlab_http_status(200)
       expect(json_response.size).to eq(2)
-      expect(json_response.map { |i| i["name"] }).to match_array([group_milestone.name, project_milestone.name])
-      expect(json_response.map { |i| i["group_name"] }.compact).to match_array(group.name)
+      expect(json_response.map { |i| i["title"] }).to match_array([group_milestone.title, project_milestone.title])
     end
 
     it 'returns closed group and project milestones to which the user belongs' do
diff --git a/spec/controllers/groups/milestones_controller_spec.rb b/spec/controllers/groups/milestones_controller_spec.rb
index bf164aeed38..48a77ac43c1 100644
--- a/spec/controllers/groups/milestones_controller_spec.rb
+++ b/spec/controllers/groups/milestones_controller_spec.rb
@@ -8,15 +8,7 @@ describe Groups::MilestonesController do
   let!(:project2) { create(:project, group: group) }
   let(:user)    { create(:user) }
   let(:title) { '肯定不是中文的问题' }
-  let(:milestone) do
-    project_milestone = create(:milestone, project: project)
-
-    GroupMilestone.build(
-      group,
-      [project],
-      project_milestone.title
-    )
-  end
+  let(:milestone) { create(:milestone, project: project) }
   let(:milestone_path) { group_milestone_path(group, milestone.safe_title, title: milestone.title) }
 
   let(:milestone_params) do
@@ -67,17 +59,16 @@ describe Groups::MilestonesController do
 
     context 'as JSON' do
       let!(:milestone) { create(:milestone, group: group, title: 'group milestone') }
-      let!(:legacy_milestone1) { create(:milestone, project: project, title: 'legacy') }
-      let!(:legacy_milestone2) { create(:milestone, project: project2, title: 'legacy') }
+      let!(:project_milestone1) { create(:milestone, project: project, title: 'same name') }
+      let!(:project_milestone2) { create(:milestone, project: project2, title: 'same name') }
 
-      it 'lists legacy group milestones and group milestones' do
+      it 'lists project and group milestones' do
         get :index, params: { group_id: group.to_param }, format: :json
 
         milestones = json_response
 
-        expect(milestones.count).to eq(2)
-        expect(milestones.first["title"]).to eq("group milestone")
-        expect(milestones.second["title"]).to eq("legacy")
+        expect(milestones.count).to eq(3)
+        expect(milestones.collect { |m| m['title'] }).to match_array(['same name', 'same name', 'group milestone'])
         expect(response).to have_gitlab_http_status(200)
         expect(response.content_type).to eq 'application/json'
       end
@@ -91,31 +82,18 @@ describe Groups::MilestonesController do
   end
 
   describe '#show' do
-    let(:milestone1) { create(:milestone, project: project, title: 'legacy') }
-    let(:milestone2) { create(:milestone, project: project, title: 'legacy') }
-    let(:group_milestone) { create(:milestone, group: group) }
+    render_views
 
-    context 'when there is a title parameter' do
-      it 'searches for a legacy group milestone' do
-        expect(GroupMilestone).to receive(:build)
-        expect(Milestone).not_to receive(:find_by_iid)
+    let!(:group_milestone) { create(:milestone, group: group) }
 
-        get :show, params: { group_id: group.to_param, id: title, title: milestone1.safe_title }
-      end
-    end
+    it 'renders for a group milestone' do
+      get :show, params: { group_id: group.to_param, id: group_milestone.iid }
 
-    context 'when there is not a title parameter' do
-      it 'searches for a group milestone' do
-        expect(GlobalMilestone).not_to receive(:build)
-        expect(Milestone).to receive(:find_by_iid)
-
-        get :show, params: { group_id: group.to_param, id: group_milestone.id }
-      end
+      expect(response).to have_gitlab_http_status(200)
+      expect(response.body).to include(group_milestone.title)
     end
   end
 
-  it_behaves_like 'milestone tabs'
-
   describe "#create" do
     it "creates group milestone with Chinese title" do
       post :create,
@@ -150,34 +128,6 @@ describe Groups::MilestonesController do
       expect(response).to redirect_to(group_milestone_path(group, milestone.iid))
       expect(milestone.title).to eq("title changed")
     end
-
-    context "legacy group milestones" do
-      let!(:milestone1) { create(:milestone, project: project, title: 'legacy milestone', description: "old description") }
-      let!(:milestone2) { create(:milestone, project: project2, title: 'legacy milestone', description: "old description") }
-
-      it "updates only group milestones state" do
-        milestone_params[:title] = "title changed"
-        milestone_params[:description] = "description changed"
-        milestone_params[:state_event] = "close"
-
-        put :update,
-             params: {
-               id: milestone1.title.to_slug.to_s,
-               group_id: group.to_param,
-               milestone: milestone_params,
-               title: milestone1.title
-             }
-
-        expect(response).to redirect_to(group_milestone_path(group, milestone1.safe_title, title: milestone1.title))
-
-        [milestone1, milestone2].each do |milestone|
-          milestone.reload
-          expect(milestone.title).to eq("legacy milestone")
-          expect(milestone.description).to eq("old description")
-          expect(milestone.state).to eq("closed")
-        end
-      end
-    end
   end
 
   describe "#destroy" do
@@ -236,52 +186,6 @@ describe Groups::MilestonesController do
           end
         end
       end
-
-      context 'when requesting a redirected path' do
-        let(:redirect_route) { group.redirect_routes.create(path: 'old-path') }
-
-        it 'redirects to the canonical path' do
-          get :merge_requests, params: { group_id: redirect_route.path, id: title }
-
-          expect(response).to redirect_to(merge_requests_group_milestone_path(group.to_param, title))
-          expect(controller).to set_flash[:notice].to(group_moved_message(redirect_route, group))
-        end
-
-        context 'when the old group path is a substring of the scheme or host' do
-          let(:redirect_route) { group.redirect_routes.create(path: 'http') }
-
-          it 'does not modify the requested host' do
-            get :merge_requests, params: { group_id: redirect_route.path, id: title }
-
-            expect(response).to redirect_to(merge_requests_group_milestone_path(group.to_param, title))
-            expect(controller).to set_flash[:notice].to(group_moved_message(redirect_route, group))
-          end
-        end
-
-        context 'when the old group path is substring of groups' do
-          # I.e. /groups/oups should not become /grfoo/oups
-          let(:redirect_route) { group.redirect_routes.create(path: 'oups') }
-
-          it 'does not modify the /groups part of the path' do
-            get :merge_requests, params: { group_id: redirect_route.path, id: title }
-
-            expect(response).to redirect_to(merge_requests_group_milestone_path(group.to_param, title))
-            expect(controller).to set_flash[:notice].to(group_moved_message(redirect_route, group))
-          end
-        end
-
-        context 'when the old group path is substring of groups plus the new path' do
-          # I.e. /groups/oups/oup should not become /grfoos
-          let(:redirect_route) { group.redirect_routes.create(path: 'oups/oup') }
-
-          it 'does not modify the /groups part of the path' do
-            get :merge_requests, params: { group_id: redirect_route.path, id: title }
-
-            expect(response).to redirect_to(merge_requests_group_milestone_path(group.to_param, title))
-            expect(controller).to set_flash[:notice].to(group_moved_message(redirect_route, group))
-          end
-        end
-      end
     end
   end
 
diff --git a/spec/features/dashboard/milestone_tabs_spec.rb b/spec/features/dashboard/milestone_tabs_spec.rb
deleted file mode 100644
index 21de7c2f06f..00000000000
--- a/spec/features/dashboard/milestone_tabs_spec.rb
+++ /dev/null
@@ -1,40 +0,0 @@
-require 'spec_helper'
-
-describe 'Dashboard milestone tabs', :js do
-  let(:user) { create(:user) }
-  let(:project) { create(:project) }
-  let!(:label) { create(:label, project: project) }
-  let(:project_milestone) { create(:milestone, project: project) }
-  let(:milestone) do
-    DashboardMilestone.build(
-      [project],
-      project_milestone.title
-    )
-  end
-  let!(:merge_request) { create(:labeled_merge_request, source_project: project, target_project: project, milestone: project_milestone, labels: [label]) }
-
-  before do
-    project.add_maintainer(user)
-    sign_in(user)
-
-    visit dashboard_milestone_path(milestone.safe_title, title: milestone.title)
-  end
-
-  it 'loads merge requests async' do
-    click_link 'Merge Requests'
-
-    expect(page).to have_selector('.milestone-merge_requests-list')
-  end
-
-  it 'loads participants async' do
-    click_link 'Participants'
-
-    expect(page).to have_selector('#tab-participants .bordered-list')
-  end
-
-  it 'loads labels async' do
-    click_link 'Labels'
-
-    expect(page).to have_selector('#tab-labels .bordered-list')
-  end
-end
diff --git a/spec/features/groups/milestone_spec.rb b/spec/features/groups/milestone_spec.rb
index d57eb87ca77..95d947854c5 100644
--- a/spec/features/groups/milestone_spec.rb
+++ b/spec/features/groups/milestone_spec.rb
@@ -100,11 +100,9 @@ describe 'Group milestones' do
         expect(find('.top-area .all .badge').text).to eq("6")
       end
 
-      it 'lists legacy group milestones and group milestones' do
-        legacy_milestone = GroupMilestone.build_collection(group, group.projects, { state: 'active' }).first
-
+      it 'lists group and project milestones' do
         expect(page).to have_selector("#milestone_#{active_group_milestone.id}", count: 1)
-        expect(page).to have_selector("#milestone_#{legacy_milestone.milestone.id}", count: 1)
+        expect(page).to have_selector("#milestone_#{active_project_milestone2.id}", count: 1)
       end
 
       it 'shows milestone detail and supports its edit' do
@@ -123,23 +121,30 @@ describe 'Group milestones' do
         expect(page).to have_content('v1.0')
         expect(page).to have_content('v1.1')
         expect(page).to have_content('GL-113')
+        expect(page).to have_link(
+          'v1.0',
+          href: project_milestone_path(project, active_project_milestone1)
+        )
         expect(page).to have_link(
           '1 Issue',
-          href: issues_group_path(group, milestone_title: 'v1.0')
+          href: project_issues_path(project, milestone_title: 'v1.0')
         )
         expect(page).to have_link(
           '0 Merge Requests',
-          href: merge_requests_group_path(group, milestone_title: 'v1.0')
+          href: project_merge_requests_path(project, milestone_title: 'v1.0')
+        )
+        expect(page).to have_link(
+          'GL-113',
+          href: group_milestone_path(group, active_group_milestone)
+        )
+        expect(page).to have_link(
+          '0 Issues',
+          href: issues_group_path(group, milestone_title: 'GL-113')
+        )
+        expect(page).to have_link(
+          '0 Merge Requests',
+          href: merge_requests_group_path(group, milestone_title: 'GL-113')
         )
-      end
-
-      it 'renders group milestone details' do
-        click_link 'v1.0'
-
-        expect(page).to have_content('expires on Aug 20, 2114')
-        expect(page).to have_content('v1.0')
-        expect(page).to have_content('Issues 1 Open: 1 Closed: 0')
-        expect(page).to have_link(issue.title, href: project_issue_path(issue.project, issue))
       end
 
       describe 'labels' do
diff --git a/spec/features/groups/milestones_sorting_spec.rb b/spec/features/groups/milestones_sorting_spec.rb
index 7bc015ea28f..633849b3c56 100644
--- a/spec/features/groups/milestones_sorting_spec.rb
+++ b/spec/features/groups/milestones_sorting_spec.rb
@@ -22,21 +22,12 @@ describe 'Milestones sorting', :js do
 
     # assert default sorting
     within '.milestones' do
-      expect(page.all('ul.content-list > li').first.text).to include('v2.0')
-      expect(page.all('ul.content-list > li')[1].text).to include('v3.0')
-      expect(page.all('ul.content-list > li').last.text).to include('v1.0')
+      expect(page.all('ul.content-list > li strong > a').map(&:text)).to eq(['v2.0', 'v2.0', 'v3.0', 'v1.0', 'v1.0'])
     end
 
     click_button 'Due soon'
 
-    sort_options = find('ul.dropdown-menu-sort li').all('a').collect(&:text)
-
-    expect(sort_options[0]).to eq('Due soon')
-    expect(sort_options[1]).to eq('Due later')
-    expect(sort_options[2]).to eq('Start soon')
-    expect(sort_options[3]).to eq('Start later')
-    expect(sort_options[4]).to eq('Name, ascending')
-    expect(sort_options[5]).to eq('Name, descending')
+    expect(find('ul.dropdown-menu-sort li').all('a').map(&:text)).to eq(['Due soon', 'Due later', 'Start soon', 'Start later', 'Name, ascending', 'Name, descending'])
 
     click_link 'Due later'
 
@@ -44,9 +35,7 @@ describe 'Milestones sorting', :js do
 
     # assert descending sorting
     within '.milestones' do
-      expect(page.all('ul.content-list > li').first.text).to include('v1.0')
-      expect(page.all('ul.content-list > li')[1].text).to include('v3.0')
-      expect(page.all('ul.content-list > li').last.text).to include('v2.0')
+      expect(page.all('ul.content-list > li strong > a').map(&:text)).to eq(['v1.0', 'v1.0', 'v3.0', 'v2.0', 'v2.0'])
     end
   end
 end
diff --git a/spec/features/milestone_spec.rb b/spec/features/milestone_spec.rb
index adac59b89ef..749f9a59209 100644
--- a/spec/features/milestone_spec.rb
+++ b/spec/features/milestone_spec.rb
@@ -109,20 +109,6 @@ describe 'Milestone' do
     end
   end
 
-  describe 'deprecation popover', :js do
-    it 'opens deprecation popover' do
-      milestone = create(:milestone, project: project)
-
-      visit group_milestone_path(group, milestone, title: milestone.title)
-
-      expect(page).to have_selector('.milestone-deprecation-message')
-
-      find('.milestone-deprecation-message .js-popover-link').click
-
-      expect(page).to have_selector('.popover')
-    end
-  end
-
   describe 'reopen closed milestones' do
     before do
       create(:milestone, :closed, project: project)
diff --git a/spec/models/global_milestone_spec.rb b/spec/models/global_milestone_spec.rb
deleted file mode 100644
index 9d901d01a52..00000000000
--- a/spec/models/global_milestone_spec.rb
+++ /dev/null
@@ -1,207 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe GlobalMilestone do
-  let(:user) { create(:user) }
-  let(:user2) { create(:user) }
-  let(:group) { create(:group) }
-  let(:project1) { create(:project, group: group) }
-  let(:project2) { create(:project, path: 'gitlab-ci', group: group) }
-  let(:project3) { create(:project, path: 'cookbook-gitlab', group: group) }
-
-  describe '.build_collection' do
-    let(:milestone1_due_date) { 2.weeks.from_now.to_date }
-
-    let!(:milestone1_project1) do
-      create(
-        :milestone,
-        title: "Milestone v1.2",
-        project: project1,
-        due_date: milestone1_due_date
-      )
-    end
-
-    let!(:milestone1_project2) do
-      create(
-        :milestone,
-        title: "Milestone v1.2",
-        project: project2,
-        due_date: milestone1_due_date
-      )
-    end
-
-    let!(:milestone1_project3) do
-      create(
-        :milestone,
-        title: "Milestone v1.2",
-        project: project3,
-        due_date: milestone1_due_date
-      )
-    end
-
-    let!(:milestone2_project1) do
-      create(
-        :milestone,
-        title: "VD-123",
-        project: project1,
-        due_date: nil
-      )
-    end
-
-    let!(:milestone2_project2) do
-      create(
-        :milestone,
-        title: "VD-123",
-        project: project2,
-        due_date: nil
-      )
-    end
-
-    let!(:milestone2_project3) do
-      create(
-        :milestone,
-        title: "VD-123",
-        project: project3,
-        due_date: nil
-      )
-    end
-
-    let!(:projects) do
-      [
-        project1,
-        project2,
-        project3
-      ]
-    end
-
-    let!(:global_milestones) { described_class.build_collection(projects, {}) }
-
-    context 'when building a collection of milestones' do
-      it 'has all project milestones' do
-        expect(global_milestones.count).to eq(6)
-      end
-
-      it 'has all project milestones titles' do
-        expect(global_milestones.map(&:title)).to match_array(['Milestone v1.2', 'Milestone v1.2', 'Milestone v1.2', 'VD-123', 'VD-123', 'VD-123'])
-      end
-
-      it 'has all project milestones' do
-        expect(global_milestones.size).to eq(6)
-      end
-
-      it 'sorts collection by due date' do
-        expect(global_milestones.map(&:due_date)).to eq [milestone1_due_date, milestone1_due_date, milestone1_due_date, nil, nil, nil]
-      end
-
-      it 'filters milestones by search_title when params[:search_title] is present' do
-        global_milestones = described_class.build_collection(projects, { search_title: 'v1.2' })
-
-        expect(global_milestones.map(&:title)).to match_array(['Milestone v1.2', 'Milestone v1.2', 'Milestone v1.2'])
-      end
-    end
-
-    context 'when adding new milestones' do
-      it 'does not add more queries' do
-        control_count = ActiveRecord::QueryRecorder.new do
-          described_class.build_collection(projects, {})
-        end.count
-
-        create_list(:milestone, 3, project: project3)
-
-        expect do
-          described_class.build_collection(projects, {})
-        end.not_to exceed_all_query_limit(control_count)
-      end
-    end
-  end
-
-  describe '.states_count' do
-    context 'when the projects have milestones' do
-      before do
-        create(:closed_milestone, title: 'Active Group Milestone', project: project3)
-        create(:active_milestone, title: 'Active Group Milestone', project: project1)
-        create(:active_milestone, title: 'Active Group Milestone', project: project2)
-        create(:closed_milestone, title: 'Closed Group Milestone', project: project1)
-        create(:closed_milestone, title: 'Closed Group Milestone', project: project2)
-        create(:closed_milestone, title: 'Closed Group Milestone', project: project3)
-        create(:closed_milestone, title: 'Closed Group Milestone 4', group: group)
-      end
-
-      it 'returns the quantity of global milestones and group milestones in each possible state' do
-        expected_count = { opened: 2, closed: 5, all: 7 }
-
-        count = described_class.states_count(Project.all, group)
-
-        expect(count).to eq(expected_count)
-      end
-
-      it 'returns the quantity of global milestones in each possible state' do
-        expected_count = { opened: 2, closed: 4, all: 6 }
-
-        count = described_class.states_count(Project.all)
-
-        expect(count).to eq(expected_count)
-      end
-    end
-
-    context 'when the projects do not have milestones' do
-      before do
-        project1
-      end
-
-      it 'returns 0 as the quantity of global milestones in each state' do
-        expected_count = { opened: 0, closed: 0, all: 0 }
-
-        count = described_class.states_count(Project.all)
-
-        expect(count).to eq(expected_count)
-      end
-    end
-  end
-
-  describe '#initialize' do
-    let(:milestone1_project1) { create(:milestone, title: "Milestone v1.2", project: project1) }
-    subject(:global_milestone) { described_class.new(milestone1_project1) }
-
-    it 'has exactly one group milestone' do
-      expect(global_milestone.title).to eq('Milestone v1.2')
-    end
-
-    it 'has all project milestones with the same title' do
-      expect(global_milestone.milestone).to eq(milestone1_project1)
-    end
-  end
-
-  describe '#safe_title' do
-    let(:milestone) { create(:milestone, title: "git / test", project: project1) }
-
-    it 'strips out slashes and spaces' do
-      global_milestone = described_class.new(milestone)
-
-      expect(global_milestone.safe_title).to eq('git-test')
-    end
-  end
-
-  describe '#state' do
-    context 'when at least one milestone is active' do
-      it 'returns active' do
-        title = 'Active Group Milestone'
-
-        global_milestone = described_class.new(create(:active_milestone, title: title))
-
-        expect(global_milestone.state).to eq('active')
-      end
-    end
-
-    context 'when all milestones are closed' do
-      it 'returns closed' do
-        title = 'Closed Group Milestone'
-
-        global_milestone = described_class.new(create(:closed_milestone, title: title))
-
-        expect(global_milestone.state).to eq('closed')
-      end
-    end
-  end
-end
diff --git a/spec/models/group_milestone_spec.rb b/spec/models/group_milestone_spec.rb
deleted file mode 100644
index 01856870fe0..00000000000
--- a/spec/models/group_milestone_spec.rb
+++ /dev/null
@@ -1,57 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe GroupMilestone do
-  let(:group) { create(:group) }
-  let(:project) { create(:project, group: group) }
-  let(:project_milestone) do
-    create(:milestone, title: "Milestone v1.2", project: project)
-  end
-
-  describe '.build' do
-    it 'returns milestone with group assigned' do
-      milestone = described_class.build(
-        group,
-        [project],
-        project_milestone.title
-      )
-
-      expect(milestone.group).to eq group
-    end
-  end
-
-  describe '.build_collection' do
-    let(:group) { create(:group) }
-    let(:project1) { create(:project, group: group) }
-    let(:project2) { create(:project, path: 'gitlab-ci', group: group) }
-    let(:project3) { create(:project, path: 'cookbook-gitlab', group: group) }
-
-    let!(:projects) do
-      [
-          project1,
-          project2,
-          project3
-      ]
-    end
-
-    it 'returns array of milestones, each with group assigned' do
-      milestones = described_class.build_collection(group, [project], {})
-      expect(milestones).to all(have_attributes(group: group))
-    end
-
-    context 'when adding new milestones' do
-      it 'does not add more queries' do
-        control_count = ActiveRecord::QueryRecorder.new do
-          described_class.build_collection(group, projects, {})
-        end.count
-
-        create(:milestone, title: 'This title', project: project1)
-
-        expect do
-          described_class.build_collection(group, projects, {})
-        end.not_to exceed_all_query_limit(control_count)
-      end
-    end
-  end
-end
diff --git a/spec/support/shared_examples/milestone_tabs_examples.rb b/spec/support/shared_examples/milestone_tabs_examples.rb
index 8b757586941..d43ac12cf6b 100644
--- a/spec/support/shared_examples/milestone_tabs_examples.rb
+++ b/spec/support/shared_examples/milestone_tabs_examples.rb
@@ -1,14 +1,6 @@
 shared_examples 'milestone tabs' do
   def go(path, extra_params = {})
-    params =
-      case milestone
-      when DashboardMilestone
-        { id: milestone.safe_title, title: milestone.title }
-      when GroupMilestone
-        { group_id: group.to_param, id: milestone.safe_title, title: milestone.title }
-      else
-        { namespace_id: project.namespace.to_param, project_id: project, id: milestone.iid }
-      end
+    params = { namespace_id: project.namespace.to_param, project_id: project, id: milestone.iid }
 
     get path, params: params.merge(extra_params)
   end
diff --git a/spec/views/shared/milestones/_top.html.haml.rb b/spec/views/shared/milestones/_top.html.haml.rb
index 516d81c87ac..045d7e6dcad 100644
--- a/spec/views/shared/milestones/_top.html.haml.rb
+++ b/spec/views/shared/milestones/_top.html.haml.rb
@@ -9,22 +9,6 @@ describe 'shared/milestones/_top.html.haml' do
     allow(milestone).to receive(:milestones) { [] }
   end
 
-  it 'renders a deprecation message for a legacy milestone' do
-    allow(milestone).to receive(:legacy_group_milestone?) { true }
-
-    render 'shared/milestones/top', milestone: milestone
-
-    expect(rendered).to have_css('.milestone-deprecation-message')
-  end
-
-  it 'renders a deprecation message for a dashboard milestone' do
-    allow(milestone).to receive(:dashboard_milestone?) { true }
-
-    render 'shared/milestones/top', milestone: milestone
-
-    expect(rendered).to have_css('.milestone-deprecation-message')
-  end
-
   it 'does not render a deprecation message for a non-legacy and non-dashboard milestone' do
     assign :group, group
 
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