Why doesn't the row_number expression update the triggering row in n8n's Google Sheets workflow?

Below is an explanation and some workarounds for the issue:

What’s Happening

Your workflow is triggered by a new row in Google Sheets, and you’re attempting to update the same row (for example, setting the “completed” column to “True”). In production runs, the trigger adds a property (row_number) that lets you target that specific row in an update statement. However, during test executions the trigger output doesn’t include the row_number property. As a result, expressions referencing it (such as constructing a range like Sheet1!G{{ $json.row_number }}) evaluate to an incomplete range (e.g. Sheet1!G) – causing the error:

  Invalid data[0]: Unable to parse range: Sheet1!G

Why This Occurs

• The row_number property is generated when a genuine trigger event occurs. Tests, however, often use static sample data that might not include row_number.
• The Google Sheets Update Row operation currently does not handle dynamic expressions for the row or range as expected when the needed property is missing.

Workarounds

1. Test with Production Data:
   Since row_number is available only in a real trigger event, try executing the workflow in production. Verify that the workflow updates the correct row when triggered by an actual event.

2. Use "Append or Update Row":
   This operation is designed to update an existing row if a matching entry is found. It might help bypass the need to manually inject the row number expression. However, it does require some kind of matching value.
   Note: You mentioned you can’t add a new unique identifier field. If you cannot use an existing unique field, this might not work for your particular setup.

3. Alternative Identification Method:
   Although you cannot add a column, consider if there’s any existing data in the row that can serve as a unique identifier for matching. This would let you use the regular update row operation by mapping automatically to the row that triggered the workflow.

Summary

The error is occurring because in test runs the row_number expression evaluates to an incomplete range (e.g. “Sheet1!G” instead of “Sheet1!G17”) due to missing data. In production, the trigger does include row_number, so the update should work as intended. Adjust your testing strategy accordingly or explore an alternative matching method if test mode is critical for your workflow debugging.

Feel free to ask if you need further clarification on any of the steps!