Remove deprecated dashboard & group milestone pages39545-cleanup-dynamic-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

32 files changed, 98 insertions, 896 deletions

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
@@ -124,22 +122,29 @@ describe 'Group milestones' do
         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