Make /manage/configuration-as-code/check respond with a JSON list of issues

[jesstruck]

What feature do you want to see added?

When sending a POST to this url <JENKINS_HOST>/manage/configuration-as-code/check with a valid JCasC file the endpoint returns status code 200 and a empty list.

when doing the exact same call but with an invalid JCasC file we get status code 500, and a HTML page with a generic stapler response saying A problem occurred while processing the request, I would expected this to return status code 200 ( 400 Bad Request / 409 Conflict or similar ) a list containing all the errors in the invalid file.

The curl command we use for succesful testing

curl --location 'https://<JENKINS_HOST>/manage/configuration-as-code/check' \
--header 'Content-Type: application/yaml' \
--header 'Authorization: Basic <token>' \
--header 'Cookie: <cookie> \
--data-raw '# Valid JCasC file
jenkins:
  systemMessage: "Welcome to Jenkins!" # Optional
  numExecutors: 2 # Default number of executors
  scmCheckoutRetryCount: 3 # Default retry count for SCM operations
 
credentials:
  system:
    domainCredentials:
      - credentials:
          - usernamePassword:
              scope: GLOBAL
              id: "admin-credentials"
              description: "Default admin credentials"
              username: "admin"
              password: "admin"
' 

The Failing command

curl --location 'https://<JENKINS_HOST>/manage/configuration-as-code/check' \
--header 'Content-Type: application/yaml' \
--header 'Authorization: Basic <token>' \
--header 'Cookie: <cookie> \
--data-raw '# Invalid JCasC file
jenkins:
  systemMessage1: "Welcome to Jenkins!" # Optional
  numExecutors: 2 # Default number of executors
  scmCheckoutRetryCount: 3 # Default retry count for SCM operations
 
credentials:
  system:
    domainCredentials:
      - credentials:
          - usernamePassword:
              scope: GLOBAL
              id: "admin-credentials"
              description: "Default admin credentials"
              username: "admin"
              password: "admin"
' 

Upstream changes

No response