DEV: emoji model should set the group of the emoji (#18237)

We do it for custom emojis but not for standard emojis which is quite unexpected and limit the use cases we can have for it.

app/models/emoji.rb

@@ -94,6 +94,7 @@ class Emoji
       e.name = name
       e.tonable = Emoji.tonable_emojis.include?(name)
       e.url = Emoji.url_for(filename)
+      e.group = groups[name] || DEFAULT_GROUP
     end
   end
 
@@ -122,6 +123,24 @@ class Emoji
     site_emoji_cache.clear
   end
 
+  def self.groups_file
+    @groups_file ||= "#{Rails.root}/lib/emoji/groups.json"
+  end
+
+  def self.groups
+    @groups ||= begin
+      groups = {}
+
+      File.open(groups_file, "r:UTF-8") { |f| JSON.parse(f.read) }.each do |group|
+        group["icons"].each do |icon|
+          groups[icon["name"]] = group["name"]
+        end
+      end
+
+      groups
+    end
+  end
+
   def self.db_file
     @db_file ||= "#{Rails.root}/lib/emoji/db.json"
   end

spec/models/emoji_spec.rb

@@ -136,4 +136,17 @@ RSpec.describe Emoji do
       expect(replaced_str).to eq("This is a good day <img src=\"/images/emoji/twitter/woman.png?v=#{Emoji::EMOJI_VERSION}\" title=\"woman\" class=\"emoji\" alt=\"woman\" loading=\"lazy\" width=\"20\" height=\"20\"> :foo: :bar:t4: :man:t8:")
     end
   end
+
+  describe ".groups" do
+    it "returns an optimized emoji name -> group name datastructure" do
+      expect(Emoji.groups["scotland"]).to eq("flags")
+    end
+  end
+
+  describe "#create_from_db_item" do
+    it "sets the group of the emoji" do
+      emoji = Emoji.create_from_db_item("name" => "scotland")
+      expect(emoji.group).to eq("flags")
+    end
+  end
 end