Use checkboxes for application scope setting (#4671)

app/controllers/settings/applications_controller.rb

@@ -5,6 +5,7 @@ class Settings::ApplicationsController < ApplicationController
 
   before_action :authenticate_user!
   before_action :set_application, only: [:show, :update, :destroy, :regenerate]
+  before_action :prepare_scopes, only: [:create, :update]
 
   def index
     @applications = current_user.applications.page(params[:page])
@@ -63,4 +64,9 @@ class Settings::ApplicationsController < ApplicationController
       :website
     )
   end
+
+  def prepare_scopes
+    scopes = params.fetch(:doorkeeper_application, {}).fetch(:scopes, nil)
+    params[:doorkeeper_application][:scopes] = scopes.join(' ') if scopes.is_a? Array
+  end
 end

app/views/settings/applications/_fields.html.haml

@@ -7,5 +7,15 @@
 
   %p.hint= t('doorkeeper.applications.help.native_redirect_uri', native_redirect_uri: Doorkeeper.configuration.native_redirect_uri)
 
-.fields-group
-  = f.input :scopes, wrapper: :with_label, label: t('activerecord.attributes.doorkeeper/application.scopes'), hint: t('doorkeeper.applications.help.scopes')
+.field-group
+  = f.input :scopes,
+    label: t('activerecord.attributes.doorkeeper/application.scopes'),
+    collection: Doorkeeper.configuration.scopes,
+    wrapper: :with_label,
+    include_blank: false,
+    selected: f.object.scopes.all,
+    required: false,
+    as: :check_boxes,
+    collection_wrapper_tag: 'ul',
+    item_wrapper_tag: 'li'
+