Power Query List Expansion Problems

Chris Webb goes over an issue with an attempt to expand out a set of folders in M:

The approach I took was the one that seemed natural to me at the time:

1. Use the Folder data source to connect to the folder containing the image files
2. Define a function called SplitText that takes a long piece of text and splits it up into a list of text values no longer than 30000 characters
3. Call the function once per row on the table returned by step (1)
4. Use the Expand/Aggregate button to expand the new column created by step (3) and get a table with one row for each of the split-up text values

When I ran this query, though, I caught sight of something that is every Power Query developer’s worst nightmare:

Read on for more. Also, drop by to congratulate Chris on collecting a blue badge.

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