Sitecore Forms Custom field gives 400 bad request when trying to add to a form via the forms interface.

Hello all.

 

On Sitecore 9.2.0, I have created a custom field, based on the relevant tutorial (https://doc.sitecore.com/developers/92/sitecore-experience-manager/en/walkthrough--creating-a-custom-rating-element-with-property-editor.html). When I try to add this field into a form via the Forms UI, I see in the network tab that the relevant API call fails with a status code of 400 (bad request). All OOTB fields work fine. Sitecore logs report absolutely nothing, event viewer reports absolutely nothing.

 

I am obviously missing something. Any insights on where to look?

  • To answer my own question, the SPEAK interface API action falls over and starts crying (with a very non-helpful 400 bad request status code and no other explanation whatsoever) if you forget to create a standard values item (empty) for your field template.