Incorrect Custom Field Type

This article examines an error that might happen when you try to update a custom field in an issue using YouTrack REST API.

You can face this error while making requests to different endpoints. This topic describes the most common scenario when you can receive this error message.

Error Message

            <class 'requests.exceptions.HTTPError'> - 500 Server Error:
            Internal Server Error for url: https://example.myjetbrains.com/youtrack/api/issues/YT-6966
            error: server_error
            error_description: class jetbrains.charisma.customfields.complex.state.
            StateProjectCustomFieldMegaProxy cannot be cast to class jetbrains.charisma.persistence.
            customfields.IssueCustomField (jetbrains.charisma.customfields.complex.state.
            StateProjectCustomFieldMegaProxy and jetbrains.charisma.persistence.customfields.
            IssueCustomField are in unnamed module of loader org.eclipse.jetty.webapp.
            WebAppClassLoader @7ec9161f)
        

Request Details

Here you can find the details about an example request that might result in this error.

Attribute	Value
Request method	POST
Endpoint	`/api/issues/issueID`
Request body	{ "customFields":[ { "name": "State", "$type": "StateProjectCustomField", "value": { "name": "Open" } } ] }
HTTP response code	500

Troubleshooting

Here you can find possible causes and suggestions on how to get rid of the error.

Cause

Your request tried to update a custom field in an issue, but the request body was referring to a custom field in a project.

Solution

Pass the corresponding issue custom field type in the request body.

The error message indicates that in this particular request, YouTrack expects an entity of the IssueCustomField type instead of StateProjectCustomField. Since IssueCustomField is an abstract ancestor for all custom fields in issues, you need to use a type of one of its descendants in the request body. In our case, it's StateIssueCustomField.

Here's the updated request body:

                        {
                            "customFields":[
                                {
                                    "name": "State",
                                    "$type": "StateIssueCustomField",
                                    "value":
                                    {
                                        "name": "Open"
                                    }
                                }
                            ]
                        }
                    

For details about custom field hierarchy in the YouTrack REST API, see Custom Fields in REST API.

Last modified: 24 February 2023