fandom: treat links to wiki pages as bad sources.

Treat sources that link to the wiki page containing the image, rather than to the image itself, as
bad sources.

This is a good source because it identifies the actual image used:

    https://typemoon.fandom.com/wiki/Astolfo?file=Memories_of_Trifas.png

This is a bad source because it doesn't identify which of the many images on the page was used:

    https://typemoon.fandom.com/wiki/Astolfo

Wiki pages are bad sources because sometimes they can have hundreds of images and it can be hard to
tell which image the post came from. Wikis can also be edited, so the image may no longer even be on
the page. Or the image could be used on multiple pages, so it can't necessarily be tied to a single
wiki page.

app/logical/source/url/fandom.rb

@@ -150,6 +150,10 @@ def image_url?
     domain == "nocookie.net"
   end
 
+  def bad_source?
+    !image_url? && file.blank?
+  end
+
   def full_image_url
     if wiki_db_name.present? && file.present?
       subdir = Digest::MD5.hexdigest(file)

test/unit/sources/fandom_test.rb

@@ -158,6 +158,17 @@ class FandomTest < ActiveSupport::TestCase
         assert(Source::URL.profile_url?("https://typemoon.fandom.com"))
         assert(Source::URL.profile_url?("https://genshin-impact.fandom.com/pt-br"))
       end
+
+      should "identify bad sources correctly" do
+        assert_not(Source::URL.parse("https://vignette.wikia.nocookie.net/valkyriecrusade/images/c/c5/Crimson_Hatsune_H.png/revision/latest?cb=20180702031954").bad_source?)
+        assert_not(Source::URL.parse("https://typemoon.fandom.com/wiki/Tamamo-no-Mae?file=Caster_Extra_Takeuchi_design_1.png").bad_source?)
+        assert_not(Source::URL.parse("https://typemoon.fandom.com/wiki/File:Memories_of_Trifas.png").bad_source?)
+
+        assert(Source::URL.parse("https://typemoon.fandom.com").bad_source?)
+        assert(Source::URL.parse("https://typemoon.fandom.com/wiki/User:Lemostr00").bad_source?)
+        assert(Source::URL.parse("https://typemoon.fandom.com/f/p/4400000000000077950").bad_source?)
+        assert(Source::URL.parse("https://genshin-impact.fandom.com/wiki/Ningguang/Gallery").bad_source?)
+      end
     end
   end
 end