A new system variable is available to get the offending 4D code that generates an error. With 4D v15 R4 whenever an error is raised you have a means to get the offending code in addition to getting the error code, as well as the method and line where the error occurred.
To do so a new system variable has been created: “Error formula”
The behavior of this new system variable is the very same as “error”, “error method” and “error line”. It is automatically filled when an error is raised and you can only use it in an error-catching method installed by the ON ERR CALL command.
For more details, please take a look at the 4D v15 R4 upgrade manual.