first_non_empty woes

[ownedbycats]

I have a bunch of individual icon rules for use in my Cleanup library; e.g. show a tag icon for missing tags, that sort of thing. Combining them into one advanced rule is proving itself to be a bit difficult though.

First I tried a gpm with a lot of elifs, only to figure out that all the 'fis' were causing processing to stop prematurely. So I thought that a first_non_empty would work better:

program: 

## Some common variables
	ids = $identifiers;

## Check for 'Cleanup' VL.
	if 'Cleanup' in virtual_libraries() then

## Begin first_non_empty
		first_non_empty(

## Missing metadata
			if !$languages then 'languages.png' fi;
			if !$#pagecount then 'cover_flow.png' fi;
			if !$#chaptercount then 'cover_flow.png' fi;
			if !$tags then 'tags.png' fi;


## Fanfiction check
			if $#fanficcat then
				status = $#fanficstatus;

## Identifiers
				if select(ids, 'url') then
					if
						'(Archive of Our Own|Fanfiction.net)' in $publisher
						&& '(Completed|Abandoned|Oneshot|Incomplete)' in status
					then 'metadata.png'
				
					elif
						!select(ids, 'ao3')
						&& $publisher == 'Archive of Our Own' 
						&& status == 'In-Progress'
					then 'metadata.png' 

					elif 
						!select(ids, 'ffnet')
						&& $publisher == 'FanFiction.net'
						&& status == 'In-Progress'
					then "metadata.png" 

					fi

				fi	
## End fanfiction check
			fi;

## Marked books 
			if is_marked() then
				m = is_marked();
				first_non_empty(
					contains(m, "invalid_author_sort|invalid_title_sort", 'auto_author_sort.png', ''),
   					contains(m, "epub_calibre_bookmarks", 'snippets.png', ''),
					if 'fff' in m && check_yes_no('#onkobo', 0, 0, 1) then 'sync.png' fi,
					if 'reading_list_send_to_device' in m then 'sync.png' fi,
					if 'reading_list_to_be_read' in m then 'list.png' fi,
					contains(m, "fff", 'download-metadata.png', ''),
					contains(m, "search_results", 'search.png', ''),
					if m then 'marked.png' fi
					)
				fi;

## Fallback to polish.png for undefined issues
			'polish.png'

## End first_non_empty
		)

# End Cleanup VL check
	fi

So I ran this on a book that should've matched one of the metadata.png tests, and instead of the expected 'metadata.png', it returned... polish.png?

Did I make a mistake? I tested this:

program: 

## Some common variables
	ids = $identifiers;

## Check for 'Cleanup' VL.
	if 'Cleanup' in virtual_libraries() then

## Fanfiction check
			if $#fanficcat then
				status = $#fanficstatus;

## Identifiers
				if select(ids, 'url') then
					if
						'(Archive of Our Own|Fanfiction.net)' in $publisher
						&& '(Completed|Abandoned|Oneshot|Incomplete)' in status
					then 'metadata.png'
				
					elif
						!select(ids, 'ao3')
						&& $publisher == 'Archive of Our Own' 
						&& status == 'In-Progress'
					then 'metadata.png' 

					elif 
						!select(ids, 'ffnet')
						&& $publisher == 'FanFiction.net'
						&& status == 'In-Progress'
					then "metadata.png" 

					fi

				fi	
## End fanfiction check
			fi

# End Cleanup VL check
	fi

returns metadata.png.

So I return to the original template and comment out polish.png (removing the semicolon on the is_marked() section). Now it's returning blank.

But if I uncomment polish.png and move the entire 'Fanfiction check' section below it, it returns metadata.png.

Did I accidentally turn my first_non_empty into a last_non_empty?

I also got some strange results on a far simpler test template:

[ownedbycats]

update: I should have used commas instead of semicolons. It was apparently just one long entry in first_non_empty instead of a bunch of them. That was a silly mistake.