Add support for markdown preview to group milestones

app/controllers/concerns/preview_markdown.rb

+module PreviewMarkdown
+  extend ActiveSupport::Concern
+
+  def preview_markdown
+    result = PreviewMarkdownService.new(@project, current_user, params).execute
+
+    markdown_params =
+      case controller_name
+      when 'wikis'    then { pipeline: :wiki, project_wiki: @project_wiki, page_slug: params[:id] }
+      when 'snippets' then { skip_project_check: true }
+      else {}
+      end
+
+    render json: {
+      body: view_context.markdown(result[:text], markdown_params),
+      references: {
+        users: result[:users],
+        commands: view_context.markdown(result[:commands])
+      }
+    }
+  end
+end

app/controllers/groups_controller.rb

@@ -2,6 +2,7 @@ class GroupsController < Groups::ApplicationController
   include IssuesAction
   include MergeRequestsAction
   include ParamsBackwardCompatibility
+  include PreviewMarkdown
 
   respond_to :html
 

app/controllers/projects/wikis_controller.rb

 class Projects::WikisController < Projects::ApplicationController
+  include PreviewMarkdown
+
   before_action :authorize_read_wiki!
   before_action :authorize_create_wiki!, only: [:edit, :create, :history]
   before_action :authorize_admin_wiki!, only: :destroy
@@ -92,17 +94,6 @@ class Projects::WikisController < Projects::ApplicationController
   def git_access
   end
 
-  def preview_markdown
-    result = PreviewMarkdownService.new(@project, current_user, params).execute
-
-    render json: {
-      body: view_context.markdown(result[:text], pipeline: :wiki, project_wiki: @project_wiki, page_slug: params[:id]),
-      references: {
-        users: result[:users]
-      }
-    }
-  end
-
   private
 
   def load_project_wiki

app/controllers/projects_controller.rb

 class ProjectsController < Projects::ApplicationController
   include IssuableCollections
   include ExtractsPath
+  include PreviewMarkdown
 
   before_action :authenticate_user!, except: [:index, :show, :activity, :refs]
   before_action :project, except: [:index, :new, :create]
@@ -258,18 +259,6 @@ class ProjectsController < Projects::ApplicationController
     render json: options.to_json
   end
 
-  def preview_markdown
-    result = PreviewMarkdownService.new(@project, current_user, params).execute
-
-    render json: {
-      body: view_context.markdown(result[:text]),
-      references: {
-        users: result[:users],
-        commands: view_context.markdown(result[:commands])
-      }
-    }
-  end
-
   private
 
   # Render project landing depending of which features are available

app/controllers/snippets_controller.rb

@@ -4,6 +4,7 @@ class SnippetsController < ApplicationController
   include SpammableActions
   include SnippetsActions
   include RendersBlob
+  include PreviewMarkdown
 
   before_action :snippet, only: [:show, :edit, :destroy, :update, :raw]
 
@@ -87,17 +88,6 @@ class SnippetsController < ApplicationController
     redirect_to snippets_path, status: 302
   end
 
-  def preview_markdown
-    result = PreviewMarkdownService.new(@project, current_user, params).execute
-
-    render json: {
-      body: view_context.markdown(result[:text], skip_project_check: true),
-      references: {
-        users: result[:users]
-      }
-    }
-  end
-
   protected
 
   def snippet

app/views/groups/milestones/_form.html.haml

@@ -10,7 +10,7 @@
       .form-group.milestone-description
         = f.label :description, "Description", class: "control-label"
         .col-sm-10
-          = render layout: 'projects/md_preview', locals: { url: '' } do
+          = render layout: 'projects/md_preview', locals: { url: group_preview_markdown_path } do
             = render 'projects/zen', f: f, attr: :description, classes: 'note-textarea', placeholder: 'Write milestone description...'
             .clearfix
             .error-alert

changelogs/unreleased/move_markdown_preview_to_concern.yml

+---
+title: Add support for markdown preview to group milestones
+merge_request: 14806
+author: Vitaliy @blackst0ne Klachkov
+type: fixed

config/routes/group.rb

 require 'constraints/group_url_constrainer'
 
-resources :groups, only: [:index, :new, :create]
+resources :groups, only: [:index, :new, :create] do
+  post :preview_markdown
+end
 
 scope(path: 'groups/*group_id',
       module: :groups,

spec/features/groups/milestone_spec.rb

@@ -18,6 +18,27 @@ feature 'Group milestones', :js do
       visit new_group_milestone_path(group)
     end
 
+    it 'renders description preview' do
+      form = find('.gfm-form')
+
+      form.fill_in(:milestone_description, with: '')
+
+      click_link('Preview')
+
+      preview = find('.js-md-preview')
+
+      expect(preview).to have_content('Nothing to preview.')
+
+      click_link('Write')
+
+      form.fill_in(:milestone_description, with: ':+1: Nice')
+
+      click_link('Preview')
+
+      expect(preview).to have_css('gl-emoji')
+      expect(find('#milestone_description', visible: false)).not_to be_visible
+    end
+
     it 'creates milestone with start date' do
       fill_in 'Title', with: 'testing'
       find('#milestone_start_date').click