Experience editor custom notifications with getPageEditorNotifications patching not working

Question

I want to show some custom Error Messages as Notifications right under the toolbar in the experience editor. I've tried to implement the Alerts from Habitat but I am not shure if this is the right thing I need and I don't get it working in my local solution.

So I am trying the PageEditorNotifications, I think this could be a solution for my problem to get a message like

but I am not able to patch the proccessor in the right place

I need it in here:

but my Patchfile tries are not working. I've tried the following Patch files:

V1

  <configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:role="http://www.sitecore.net/xmlconfig/role/">
    <sitecore role:require="Standalone or ContentManagement">
      <group groupName="ExperienceEditor" name="ExperienceEditor">
        <pipelines>
          <getPageEditorNotifications>
            <processor type="Foundation.ExperienceEditor.Pipelines.ShowCustomNotifications, Foundation.ExperienceEditor" patch:after="processor[@type='Sitecore.ContentTesting.Pipelines.GetPageEditorNotifications.GetContentTestingNotifications, Sitecore.ContentTesting']" />
          </getPageEditorNotifications>
        </pipelines>
      </group>
    </sitecore>
  </configuration>

V2

<configuration xmlns:patch="sitecore.net/xmlconfig" xmlns:set="sitecore.net/xmlconfig/set">
  <sitecore>
    <pipelines>
      <getPageEditorNotifications>
        <processor type="Foundation.ExperienceEditor.Pipelines.ShowCustomNotifications, Foundation.ExperienceEditor" />
      </getPageEditorNotifications>
    </pipelines>
  </sitecore>
</configuration>

V3

<configuration xmlns:patch="sitecore.net/xmlconfig" xmlns:set="sitecore.net/xmlconfig/set">
  <sitecore>
      <getPageEditorNotifications>
        <processor type="Foundation.ExperienceEditor.Pipelines.ShowCustomNotifications, Foundation.ExperienceEditor" />
      </getPageEditorNotifications>
  </sitecore>
</configuration>

but non of them is patching the right location :-/ so that the processor get called. I am using Sitecore 9 update 2

processor code:

    namespace Foundation.ExperienceEditor.Pipelines
    {
        public class ShowCustomNotifications : GetPageEditorNotificationsProcessor
        {
            public override void Process(GetPageEditorNotificationsArgs arguments)
            {
                arguments.Notifications.Add(new PageEditorNotification("Hallo Welt", PageEditorNotificationType.Error));
            }      
        }
    }

Answer 1

It's not intuitive with pipeline processors and group configs - you need to have first pipelines, then group and then again pipelines node.

This is the correct patch file:

<?xml version="1.0" encoding="utf-8"?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:role="http://www.sitecore.net/xmlconfig/role/">
  <sitecore role:require="Standalone or ContentManagement or ContentDelivery or Reporting or Processing">
    <pipelines>
      <group groupName="ExperienceEditor" name="ExperienceEditor">
        <pipelines>
          <getPageEditorNotifications>
            <processor 
              type="Foundation.ExperienceEditor.Pipelines.ShowCustomNotifications, Foundation.ExperienceEditor" 
              patch:after="processor[@type='Sitecore.ContentTesting.Pipelines.GetPageEditorNotifications.GetContentTestingNotifications, Sitecore.ContentTesting']" />
          </getPageEditorNotifications>
        </pipelines>
      </group>
    </pipelines>
  </sitecore>
</configuration>