[[processors.parser]] merge with more than one parsed metric does not work

[1tft]

Relevant telegraf.conf

[[inputs.file]]
  files = [ "/tmp/mydata.txt" ]
  data_format = "grok"
  grok_patterns = ['''
    %{MULTILINEDATA:logmessage}
  ''']
  grok_multiline = true
  name_override = "prometheus" # same name as later parsed data from payload

  [inputs.file.tags]
    mytag = "mytagvalue"

[[processors.parser]]
  data_format = "prometheus"
  parse_fields = ["logmessage"]
  drop_original = false
  merge = "override" # Case one
  #merge = "" # Case two


[[processors.rename]]
  fieldexclude = ["logmessage"]
  [[processors.rename.replace]]
    measurement = "prometheus"
    dest = "mymeasurement"

Logs from Telegraf

na

System info

Telegraf 1.32.1

Docker

No response

Steps to reproduce

1. Create /tmp/mydata.txt with following data:

# HELP mycount my cool counter
# TYPE mycount gauge
mycount{mylabel="labelvalue01"} 66
mycount{mylabel="labelvalue02"} 77

2. Run config above (telegraf -config /etc/telegraf/telegraf.d/my_issue -test)
   ...

Expected behavior

Output:

mymeasurement,host=XYZ,mylabel=labelvalue01,mytag=mytagvalue mycount=66 1736354163000000000
mymeasurement,host=XYZ,mylabel=labelvalue02,mytag=mytagvalue mycount=77 1736354163000000000

All parsed metrics are merged with inital input metric.

Actual behavior

Output:

mymeasurement,host=XYZ,mylabel=labelvalue02,mytag=mytagvalue mycount=77 1736354163000000000

All metrics but one have been lost.

Additional info

For this example we can solve all issues when we parse prometheus already in inputs plugin (and not use grok).
But our real life issue is based on [[inputs.win_eventlog]], there we cant set data_format to "prometheus" inside inputs plugin.

Currently we solve this issue with merge = "" but this means all global tags are lost including "host" tag. Also tag mytag = "mytagvalue" is lost which we need for flow control because we use multiple configs on same host. Thats our main issue: We dont know how we can "transfer" our [inputs.file.tags] and agent.conf global tags to any metric generated by [[processors.parser]], without specifying duplicated manually via processors.starlark or processors.override.

[1tft]

FYI: Currently there also another issue #16331 open for [[processors.parser]]