Improve displaying validation messages for runner

app/controllers/projects/runners_controller.rb

@@ -20,7 +20,6 @@ class Projects::RunnersController < Projects::ApplicationController
     if @runner.update_attributes(runner_params)
       redirect_to runner_path(@runner), notice: 'Runner was successfully updated.'
     else
-      flash[:alert] = @runner.errors.full_messages.to_sentence
       render 'edit'
     end
   end

app/models/ci/runner.rb

@@ -27,9 +27,9 @@ module Ci
     end
 
     validate do |runner|
-      if runner.tag_list.empty? && !runner.run_untagged?
-        errors.add(:tags_errors,
-          'Runner without tags must be able to pick untagged jobs!')
+      unless runner.has_tags? || runner.run_untagged?
+        errors.add(:tags_list,
+          'can not be empty when runner is not allowed to pick untagged jobs')
       end
     end
 
@@ -103,5 +103,9 @@ module Ci
     def short_sha
       token[0...8] if token
     end
+
+    def has_tags?
+      tag_list.any?
+    end
   end
 end

app/views/projects/runners/edit.html.haml

 - page_title "Edit", "#{@runner.description} ##{@runner.id}", "Runners"
 
 %h4 Runner ##{@runner.id}
+
+- if @runner.errors.any?
+  .error-message.js-errors
+    - @runner.errors.full_messages.each do |error|
+      %div= error
+
 %hr
  = render 'form', runner: @runner, runner_form_url: runner_path(@runner)