remove_field is executed before dissection (regression from version 7.8.1 -> 7.10.1)

[fkellner]

• Logstash Version: 7.10.1
• Operating System: Ubuntu 18.04 LTS
• Steps to reproduce:

The following configuration worked fine in Logstash Version 7.8.1:

  dissect {
    mapping => {
      "message" => "%{}<Stuff>%{tables}<other Stuff>%{}"
    }
    remove_field => ["message"]
  }

After upgrading to 7.10.1, it produced a Dissectfailure/Warning that the "message"-field could not be found.

I tested with the file output and the message field was part of the event before it reached the dissect block.
After moving the remove_field option to a later block, everything works fine again, so I would guess that the execution order of the common options has changed to before the filter.

I do not know if I should file it here or it is a logstash issue - personally, I think being able to remove a field after dissecting it without needing to open a new filter block was the more readable solution.