When using Advanced Python label expressions (e.g., defining a custom FindLabel function), the Summary tool in ArcGIS Pro reports misleading errors such as:
Label expression is invalid.
Carriage returns are not allowed in simple expressions.
No function was found with the name 'FindLabel'.
Despite these warnings, the labels display correctly in the map and the Python expression validates successfully in the Label Class dialog. The problem is not with the expression itself, but with the way the Summary tool attempts to validate label expressions as if they were simple expressions only.
Impact
- Users may believe their label expressions are broken, even though they work correctly.
- This creates unnecessary confusion and undermines confidence in the labeling workflow.
Suggested correction
Instead of reporting the expression as “invalid,” the Summary tool should recognize when a label class is using an Advanced expression and display a more accurate message, for example:
“Advanced label expression detected. Expression not validated by Summary tool.”
This would make it clear that the expression is outside the scope of the simple validator, while reassuring users that their labels may still function as expected.
