search: support negated wildcards in post searches.

* Support negated wildcards in searches (e.g. "holding -holding_*")
* Raise wildcard limit to matching 25 tags regardless of user level.
* Fix wildcards potentially matching empty tags.
* Fix wildcard tags being sorted by post count only, and therefore not
  having a stable ordering when tags have equal post counts.
* Fix sidebar to calculate wildcards tags the same way the search does.

app/logical/post_query_builder.rb

@@ -1033,20 +1033,36 @@ class PostQueryBuilder
         return q
       end
 
-      def parse_tag(tag, output)
-        if tag[0] == "-" && tag.size > 1
-          output[:exclude] << tag[1..-1].mb_chars.downcase
-
-        elsif tag[0] == "~" && tag.size > 1
-          output[:include] << tag[1..-1].mb_chars.downcase
-
-        elsif tag =~ /\*/
-          matches = Tag.name_matches(tag).select("name").limit(Danbooru.config.tag_query_limit).order("post_count DESC").map(&:name)
-          matches = ["~no_matches~"] if matches.empty?
-          output[:include] += matches
+      def parse_tag_operator(tag)
+        tag = Tag.normalize_name(tag)
 
+        if tag.starts_with?("-")
+          ["-", tag.delete_prefix("-")]
+        elsif tag.starts_with?("~")
+          ["~", tag.delete_prefix("~")]
         else
-          output[:related] << tag.mb_chars.downcase
+          [nil, tag]
+        end
+      end
+
+      def parse_tag(tag, output)
+        operator, tag = parse_tag_operator(tag)
+
+        if tag.include?("*")
+          tags = Tag.wildcard_matches(tag)
+
+          if operator == "-"
+            output[:exclude] += tags
+          else
+            tags = ["~no_matches~"] if tags.empty? # force empty results if wildcard found no matches.
+            output[:include] += tags
+          end
+        elsif operator == "-"
+          output[:exclude] << tag
+        elsif operator == "~"
+          output[:include] << tag
+        else
+          output[:related] << tag
         end
       end
 

app/models/tag.rb

@@ -279,6 +279,10 @@ class Tag < ApplicationRecord
       name_matches(name).or(alias_matches(name))
     end
 
+    def wildcard_matches(tag, limit: 25)
+      nonempty.name_matches(tag).order(post_count: :desc, name: :asc).limit(limit).pluck(:name)
+    end
+
     def search(params)
       q = super
 

app/presenters/post_set_presenters/post.rb

@@ -48,7 +48,7 @@ module PostSetPresenters
     end
 
     def pattern_tags
-      Tag.name_matches(post_set.tag_string).order(post_count: :desc).limit(MAX_TAGS).pluck(:name)
+      Tag.wildcard_matches(post_set.tag_string)
     end
 
     def saved_search_tags

test/unit/post_test.rb

@@ -1962,6 +1962,18 @@ class PostTest < ActiveSupport::TestCase
       assert_tag_match([post2], "a* bbb")
     end
 
+    should "return posts for a negated pattern" do
+      post1 = create(:post, tag_string: "aaa")
+      post2 = create(:post, tag_string: "aaab bbb")
+      post3 = create(:post, tag_string: "bbb ccc")
+
+      assert_tag_match([post3], "-a*")
+      assert_tag_match([post3], "bbb -a*")
+      assert_tag_match([post3], "~bbb -a*")
+      assert_tag_match([post1], "a* -*b")
+      assert_tag_match([post2], "-*c -a*a")
+    end
+
     should "return posts for the id:<N> metatag" do
       posts = FactoryBot.create_list(:post, 3)