support reacting with foreign custom emojis

app/models/status_reaction.rb

@@ -24,11 +24,6 @@ class StatusReaction < ApplicationRecord
   private
 
   def set_custom_emoji
-    return if name.blank?
+    self.custom_emoji = CustomEmoji.find_by(shortcode: name, domain: account.domain) if name.blank?
-    self.custom_emoji = if account.local?
-                          CustomEmoji.local.find_by(disabled: false, shortcode: name)
-                        else
-                          CustomEmoji.find_by(shortcode: name, domain: account.domain)
-                        end
   end
 end

app/serializers/rest/reaction_serializer.rb

@@ -3,7 +3,7 @@
 class REST::ReactionSerializer < ActiveModel::Serializer
   include RoutingHelper
 
-  attributes :name, :count, :extern
+  attributes :name, :count
 
   attribute :me, if: :current_user?
   attribute :url, if: :custom_emoji?
@@ -21,11 +21,11 @@ class REST::ReactionSerializer < ActiveModel::Serializer
     object.custom_emoji.present?
   end
 
-  def extern
+  def name
-    if custom_emoji?
+    if extern?
-      object.custom_emoji.domain.present?
+      [object.name, '@', object.custom_emoji.domain].join
     else
-      false
+      object.name
     end
   end
 
@@ -36,4 +36,10 @@ class REST::ReactionSerializer < ActiveModel::Serializer
   def static_url
     full_asset_url(object.custom_emoji.image.url(:static))
   end
+
+  private
+
+  def extern?
+    custom_emoji? && object.custom_emoji.domain.present?
+  end
 end

app/validators/status_reaction_validator.rb

@@ -18,10 +18,6 @@ class StatusReactionValidator < ActiveModel::Validator
     SUPPORTED_EMOJIS.include?(name)
   end
 
-  def new_reaction?(reaction)
-    !reaction.status.status_reactions.where(name: reaction.name).exists?
-  end
-
   def limit_reached?(reaction)
     reaction.status.status_reactions.where(status: reaction.status, account: reaction.account).count >= LIMIT
   end

config/routes.rb

@@ -442,8 +442,10 @@ Rails.application.routes.draw do
           resource :favourite, only: :create
           post :unfavourite, to: 'favourites#destroy'
 
-          post '/react/:id', to: 'reactions#create'
+          # foreign custom emojis are encoded as shortcode@domain.tld
-          post '/unreact/:id', to: 'reactions#destroy'
+          # the constraint prevents rails from interpreting the ".tld" as a filename extension
+          post '/react/:id', to: 'reactions#create', constraints: { id: /[^\/]+/ }
+          post '/unreact/:id', to: 'reactions#destroy', constraints: { id: /[^\/]+/ }
 
           resource :bookmark, only: :create
           post :unbookmark, to: 'bookmarks#destroy'