idea Label Expression Validation in ArcGIS Pro in ArcGIS Pro Ideas

Label Expression Validation in ArcGIS Pro

MarcelSt-Germain — Tue, 21 Oct 2025 18:34:06 GMT

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.

Re: Label Expression Validation in ArcGIS Pro - Status changed to: Needs Clarification

CraigWilliams — Tue, 21 Oct 2025 22:42:05 GMT

Marcel, Can you provide an example of the expression you're experiencing this with? I'm unable to reproduce this with a FindLabel function (which we look for to detect the advanced expression)

Re: Label Expression Validation in ArcGIS Pro

MarcelSt-Germain — Wed, 22 Oct 2025 13:19:45 GMT

First, why can't we be able to work when Labeling Summary is open. We have to copy and paste in text but, then, we lost formatting (no color, no indentation) ??? So make the Labeling Summary available or format when copying.

Issues (0) but, this is one exemple of the return.

Python advanced script is validated, show in map but still generated the warning.

Group Layer: Version ENC5 EN-FR m

Group Layer: ***ENC principaux

Font: Arial Narrow-Bold; TTOpenType

Layer: point_light : ML m/ ft

Label Class: INFO light

Labeled class.

SQL Query not defined. All features will be added to the placement engine.

Label expression is invalid. Invalid Expression.

Carriage returns are not allowed in simple expressions.

No function was found with the name 'findLabel'.

Re: Label Expression Validation in ArcGIS Pro - Status changed to: Closed

CraigWilliams — Thu, 23 Oct 2025 17:50:14 GMT

We've identified the issue and logged BUG-000180302. Since Ideas isn't intended for bug submission, I will close this Idea.