search: split tag_match into user_tag_match / system_tag_match.

When doing a tag search, we have to be careful about which user we're
running the search as because the results depend on the current user.
Specifically, things like private favorites, private favorite groups,
post votes, saved searches, and flagger names depend on the user's
permissions, and whether non-safe or deleted posts are filtered out
depend on whether the user has safe mode on or the hide deleted posts
setting enabled.

* Refactor internal searches to explicitly state whether they're
  running as the system user (DanbooruBot) or as the current user.
* Explicitly pass in the current user to PostQueryBuilder instead of
  implicitly relying on the CurrentUser global.
* Get rid of CurrentUser.admin_mode? (used to ignore the hide deleted
  post setting) and CurrentUser.without_safe_mode (used to ignore safe
  mode).
* Change the /counts/posts.json endpoint to ignore safe mode and the
  hide deleted posts settings when counting posts.
* Fix searches not correctly overriding the hide deleted posts setting
  when multiple status: metatags were used (e.g. `status:banned status:active`)
* Fix fast_count not respecting the hide deleted posts setting when the
  status:banned metatag was used.

app/models/artist.rb

@@ -134,10 +134,8 @@ class Artist < ApplicationRecord
       source = params.delete(:source)
 
       if source.blank? && params[:name].present?
-        CurrentUser.without_safe_mode do
-          post = Post.tag_match("source:http* #{params[:name]}").first
-          source = post.try(:source)
-        end
+        post = Post.system_tag_match("source:http* #{params[:name]}").first
+        source = post.try(:source)
       end
 
       if source.present?
@@ -168,36 +166,32 @@ class Artist < ApplicationRecord
   module BanMethods
     def unban!
       Post.transaction do
-        CurrentUser.without_safe_mode do
-          ti = TagImplication.find_by(antecedent_name: name, consequent_name: "banned_artist")
-          ti&.destroy
+        ti = TagImplication.find_by(antecedent_name: name, consequent_name: "banned_artist")
+        ti&.destroy
 
-          Post.tag_match(name).find_each do |post|
-            post.unban!
-            fixed_tags = post.tag_string.sub(/(?:\A| )banned_artist(?:\Z| )/, " ").strip
-            post.update(tag_string: fixed_tags)
-          end
-
-          update!(is_banned: false)
-          ModAction.log("unbanned artist ##{id}", :artist_unban)
+        Post.raw_tag_match(name).find_each do |post|
+          post.unban!
+          fixed_tags = post.tag_string.sub(/(?:\A| )banned_artist(?:\Z| )/, " ").strip
+          post.update(tag_string: fixed_tags)
         end
+
+        update!(is_banned: false)
+        ModAction.log("unbanned artist ##{id}", :artist_unban)
       end
     end
 
     def ban!(banner: CurrentUser.user)
       Post.transaction do
-        CurrentUser.without_safe_mode do
-          Post.tag_match(name).each(&:ban!)
+        Post.raw_tag_match(name).each(&:ban!)
 
-          # potential race condition but unlikely
-          unless TagImplication.where(:antecedent_name => name, :consequent_name => "banned_artist").exists?
-            tag_implication = TagImplication.create!(antecedent_name: name, consequent_name: "banned_artist", skip_secondary_validations: true, creator: banner)
-            tag_implication.approve!(approver: banner)
-          end
-
-          update!(is_banned: true)
-          ModAction.log("banned artist ##{id}", :artist_ban)
+        # potential race condition but unlikely
+        unless TagImplication.where(:antecedent_name => name, :consequent_name => "banned_artist").exists?
+          tag_implication = TagImplication.create!(antecedent_name: name, consequent_name: "banned_artist", skip_secondary_validations: true, creator: banner)
+          tag_implication.approve!(approver: banner)
         end
+
+        update!(is_banned: true)
+        ModAction.log("banned artist ##{id}", :artist_ban)
       end
     end
   end

app/models/pool.rb

@@ -27,7 +27,7 @@ class Pool < ApplicationRecord
     end
 
     def post_tags_match(query)
-      posts = Post.tag_match(query).select(:id).reorder(nil)
+      posts = Post.user_tag_match(query).select(:id).reorder(nil)
       pools = Pool.joins("CROSS JOIN unnest(post_ids) AS post_id").group(:id).where("post_id IN (?)", posts)
       where(id: pools)
     end

app/models/post.rb

@@ -604,7 +604,7 @@ class Post < ApplicationRecord
         # If someone else committed changes to this post before we did,
         # then try to merge the tag changes together.
         current_tags = tag_string_was.split
-        new_tags = PostQueryBuilder.new(tag_string).parse_tag_edit
+        new_tags = PostQueryBuilder.new(tag_string).split_query
         old_tags = old_tag_string.split
 
         kept_tags = current_tags & new_tags
@@ -642,7 +642,7 @@ class Post < ApplicationRecord
     end
 
     def normalize_tags
-      normalized_tags = PostQueryBuilder.new(tag_string).parse_tag_edit
+      normalized_tags = PostQueryBuilder.new(tag_string).split_query
       normalized_tags = apply_casesensitive_metatags(normalized_tags)
       normalized_tags = normalized_tags.map(&:downcase)
       normalized_tags = filter_metatags(normalized_tags)
@@ -1372,9 +1372,7 @@ class Post < ApplicationRecord
     end
 
     def sample(query, sample_size)
-      CurrentUser.without_safe_mode do
-        tag_match(query).reorder(:md5).limit(sample_size)
-      end
+      user_tag_match(query, safe_mode: false, hide_deleted_posts: false).reorder(:md5).limit(sample_size)
     end
 
     # unflattens the tag_string into one tag per row.
@@ -1472,8 +1470,12 @@ class Post < ApplicationRecord
       where("posts.tag_index @@ to_tsquery('danbooru', E?)", tag.to_escaped_for_tsquery)
     end
 
-    def tag_match(query)
-      PostQueryBuilder.new(query).build
+    def system_tag_match(query)
+      user_tag_match(query, User.system, safe_mode: false, hide_deleted_posts: false)
+    end
+
+    def user_tag_match(query, user = CurrentUser.user, safe_mode: CurrentUser.safe_mode?, hide_deleted_posts: user.hide_deleted_posts?)
+      PostQueryBuilder.new(query, user, safe_mode: safe_mode, hide_deleted_posts: hide_deleted_posts).build
     end
 
     def search(params)
@@ -1488,7 +1490,7 @@ class Post < ApplicationRecord
       )
 
       if params[:tags].present?
-        q = q.tag_match(params[:tags])
+        q = q.user_tag_match(params[:tags])
       end
 
       if params[:order].present?

app/models/saved_search.rb

@@ -114,18 +114,16 @@ class SavedSearch < ApplicationRecord
       end
 
       def populate(query, timeout: 10_000)
-        CurrentUser.as_system do
-          redis_key = "search:#{query}"
-          return if redis.exists(redis_key)
+        redis_key = "search:#{query}"
+        return if redis.exists(redis_key)
 
-          post_ids = Post.with_timeout(timeout, [], query: query) do
-            Post.tag_match(query).limit(QUERY_LIMIT).pluck(:id)
-          end
+        post_ids = Post.with_timeout(timeout, [], query: query) do
+          Post.system_tag_match(query).limit(QUERY_LIMIT).pluck(:id)
+        end
 
-          if post_ids.present?
-            redis.sadd(redis_key, post_ids)
-            redis.expire(redis_key, REDIS_EXPIRY.to_i)
-          end
+        if post_ids.present?
+          redis.sadd(redis_key, post_ids)
+          redis.expire(redis_key, REDIS_EXPIRY.to_i)
         end
       end
     end

app/models/tag.rb

@@ -349,7 +349,7 @@ class Tag < ApplicationRecord
   end
 
   def posts
-    Post.tag_match(name)
+    Post.system_tag_match(name)
   end
 
   def self.available_includes