AO3-6811 Fix tag nomination parented bug

[pmonfort]

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Issue

https://otwarchive.atlassian.net/browse/AO3-6811

Purpose

When a canonical tag is saved, Tag#update_tag_nominations sets parented: true on matching TagNomination records.
However, it only checked for Fandom-type parents and only matched nominations with a blank parent_tagname (empty string).
This caused nominations to be incorrectly marked as parented: false when:

• The tag's parent was a non-Fandom type (e.g., a Media parent on a Fandom tag).
• The nomination had a nil parent_tagname instead of an empty string.

This PR fixes both issues by:

1. Checking all parent types instead of only Fandoms.
2. Including both "" and nil in the parent_names list so nominations with either blank value are matched.

Testing Instructions

1. Create a canonical fandom tag with a Media parent (but no Fandom parent).
2. Create a tag nomination for that fandom in a tag set.
3. Save the fandom tag.
4. Verify the nomination's parented field is true.

Credit

Pablo Monfort (he/him)

[sarken]

Assigning myself as reviewer since I saw some things I want to poke at, but I am beat so that's not gonna happen tonight

[sarken]

Thanks for working on this! I've updated the Jira issue with new testing steps and just have one question about this code.

[sarken]

I'm not sure this is necessary. A nomination's parent_tagname should always be the name of a fandom unless the nominated tag itself is a fandom. For fandom nominations, it seems like the parent_tagname is always nil, never the name of a media tag. I took a look at staging to confirm:

3.4.6 :001 > noms = FandomNomination.where("parent_tagname IS NOT NULL") ; nil
 => nil 
3.4.6 :002 > noms.size
 => 0 
3.4.6 :003 > noms = FandomNomination.where(parent_tagname: "") ; nil
 => nil 
3.4.6 :004 > noms.size
 => 0 
3.4.6 :005 > noms = FandomNomination.where(parent_tagname: nil) ; nil
 => nil 
3.4.6 :006 > noms.size
 => 21488 
3.4.6 :007 > FandomNomination.all.count
 => 21488

Can you think of a scenario in which we'd expect to find a tag nomination with a non-fandom, non-blank, and non-nil parent_tagname?

[pmonfort]

You're right that fandom nominations always have parent_tagname: nil and the media parent name itself won't directly match any nomination. But after digging deeper, I think removing the type filter is still needed, looking at https://github.com/otwcode/otwarchive/blob/master/app/models/fandom.rb#L44 a Fandom's parent_types are either Media or MetaTag which means parents.where(type: "Fandom") would always return [] for any fandom tag. So parent_names.present? would always be false, nil would never get added, and the update_all would match nothing, leaving the nominations as parented: false

I admit the fix is a bit indirect though, the media parent names in the list won't match anything, but they make parent_names non-empty so that nil gets added on line 1259, which is what actually matches the fandom nominations.

Maybe this would be a cleaner approach.

if canonical? && parents.exists?
  parent_names = parents.where(type: "Fandom").pluck(:name).push("", nil)
  TagNomination.where(tagname: name, parent_tagname: parent_names).update_all(parented: true)
end

@sarken thanks for you review! Let me know your thoughts