Weird error using config API v2 with Solr 9.8.1 to add UpdateProcessor (Followup of "Current core has 1206 fields, exceeding the max-fields limit of 1000")

[Andreas Mock]

Hi all,

after Chris Hostetter gave me some hints with my problem of exceeding a default 
limit, I wanted to change this limit using the config API as described in the 
documentation
(https://solr.apache.org/guide/solr/latest/configuration-guide/config-api.html)

When trying to change an existing updateprocessor or adding a new one I get an 
error message which I can't explain to myself:
Example:

curl -v  -X POST -H 'Content-type:application/json' -d 
'{"add-updateprocessor":{"maxFields":999,"class":"solr.NumFieldLimitingUpdateRequestProcessorFactory","warnOnly":"true","name":"test-fields"}}'
 
http://<http://q-solr9-09.drumedar.intern:9983/api/collections/mca_test/config>solr-host:9983/api/collections/mca_test/config<http://q-solr9-09.drumedar.intern:9983/api/collections/mca_test/config>

I get the error:
{
  "responseHeader":{
    "status":400,
    "QTime":2
  },
  "errorMessages":["error processing commands, errors: 
[{errorMessages=[maxFields must be configured as a non-null <int>], 
add-updateprocessor={maxFields=999, 
class=solr.NumFieldLimitingUpdateRequestProcessorFactory, warnOnly=true, 
name=test-fields}}], \n"],
  "WARNING":"This response format is experimental.  It is likely to change in 
the future.",
  "error":{
    
"metadata":["error-class","org.apache.solr.api.ApiBag$ExceptionWithErrObject","root-error-class","org.apache.solr.api.ApiBag$ExceptionWithErrObject"],
    "details":[{
      "errorMessages":["maxFields must be configured as a non-null <int>"],
      "add-updateprocessor":{
        "maxFields":999,
        "class":"solr.NumFieldLimitingUpdateRequestProcessorFactory",
        "warnOnly":"true",
        "name":"test-fields"
      }
    }],
    "msg":"error processing commands, errors: [{errorMessages=[maxFields must 
be configured as a non-null <int>], add-updateprocessor={maxFields=999, 
class=solr.NumFieldLimitingUpdateRequestProcessorFactory, warnOnly=true, 
name=test-fields}}], ",
    "code":400
  }

As you can see I declared maxFields to 999 as a JSON number. First I thought I 
gave the wrong structure, but as soon as I don't give  maxFields, I get an 
error stating that maxFileds is a required attribute. So, I'm pretty sure to 
build the right JSON structure.

Any help really appreciated.

Best regards
Andreas