Merge pull request #2416 from basecamp/introduce-reactable

Make `Reaction` polymorphic with `reactable` association

app/models/comment.rb

@@ -4,7 +4,7 @@ class Comment < ApplicationRecord
   belongs_to :account, default: -> { card.account }
   belongs_to :card, touch: true
   belongs_to :creator, class_name: "User", default: -> { Current.user }
-  has_many :reactions, -> { order(:created_at) }, dependent: :delete_all
+  has_many :reactions, -> { order(:created_at) }, as: :reactable, dependent: :delete_all
 
   has_rich_text :body
 

app/models/reaction.rb

@@ -1,6 +1,6 @@
 class Reaction < ApplicationRecord
-  belongs_to :account, default: -> { comment.account }
+  belongs_to :account, default: -> { reactable.account }
-  belongs_to :comment, touch: true
+  belongs_to :reactable, polymorphic: true, touch: true
   belongs_to :reacter, class_name: "User", default: -> { Current.user }
 
   scope :ordered, -> { order(:created_at) }
@@ -11,6 +11,6 @@ class Reaction < ApplicationRecord
 
   private
     def register_card_activity
-      comment.card.touch_last_active_at
+      reactable.card.touch_last_active_at
     end
 end

app/views/cards/comments/reactions/_reaction.html.erb

@@ -15,7 +15,7 @@
         class: [ "txt-small", { "txt-medium": reaction.all_emoji? } ],
         data: { action: "click->reaction-delete#reveal keydown.enter->reaction-delete#reveal:prevent", reaction_delete_target: "content" } %>
 
-  <%= button_to card_comment_reaction_path(reaction.comment.card, reaction.comment, reaction),
+  <%= button_to card_comment_reaction_path(reaction.reactable.card, reaction.reactable, reaction),
         method: :delete,
         class: "reaction__delete btn btn--negative flex-item-justify-end",
         data: { action: "reaction-delete#perform", reaction_delete_target: "button" } do %>

app/views/cards/comments/reactions/_reaction.json.jbuilder

@@ -1,5 +1,5 @@
 json.cache! reaction do
   json.(reaction, :id, :content)
   json.reacter reaction.reacter, partial: "users/user", as: :user
-  json.url card_comment_reaction_url(reaction.comment.card, reaction.comment, reaction)
+  json.url card_comment_reaction_url(reaction.reactable.card, reaction.reactable, reaction)
 end

db/migrate/20260121155752_make_reactions_polymorphic.rb

@@ -0,0 +1,27 @@
+class MakeReactionsPolymorphic < ActiveRecord::Migration[8.0]
+  def change
+    add_column :reactions, :reactable_type, :string
+    add_column :reactions, :reactable_id, :uuid
+
+    reversible do |dir|
+      dir.up do
+        execute <<~SQL
+          UPDATE reactions SET reactable_type = 'Comment', reactable_id = comment_id
+        SQL
+      end
+
+      dir.down do
+        execute <<~SQL
+          UPDATE reactions SET comment_id = reactable_id WHERE reactable_type = 'Comment'
+        SQL
+      end
+    end
+
+    change_column_null :reactions, :reactable_type, false
+    change_column_null :reactions, :reactable_id, false
+
+    remove_column :reactions, :comment_id, :uuid
+
+    add_index :reactions, [:reactable_type, :reactable_id]
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.2].define(version: 2025_12_24_092315) do
+ActiveRecord::Schema[8.2].define(version: 2026_01_21_155752) do
   create_table "accesses", id: :uuid, charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.datetime "accessed_at"
     t.uuid "account_id", null: false
@@ -412,13 +412,14 @@ ActiveRecord::Schema[8.2].define(version: 2025_12_24_092315) do
 
   create_table "reactions", id: :uuid, charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.uuid "account_id", null: false
-    t.uuid "comment_id", null: false
     t.string "content", limit: 16, null: false
     t.datetime "created_at", null: false
+    t.uuid "reactable_id", null: false
+    t.string "reactable_type", null: false
     t.uuid "reacter_id", null: false
     t.datetime "updated_at", null: false
     t.index ["account_id"], name: "index_reactions_on_account_id"
-    t.index ["comment_id"], name: "index_reactions_on_comment_id"
+    t.index ["reactable_type", "reactable_id"], name: "index_reactions_on_reactable_type_and_reactable_id"
     t.index ["reacter_id"], name: "index_reactions_on_reacter_id"
   end
 

db/schema_sqlite.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.2].define(version: 2025_12_24_092315) do
+ActiveRecord::Schema[8.2].define(version: 2026_01_21_155752) do
   create_table "accesses", id: :uuid, force: :cascade do |t|
     t.datetime "accessed_at"
     t.uuid "account_id", null: false
@@ -412,13 +412,14 @@ ActiveRecord::Schema[8.2].define(version: 2025_12_24_092315) do
 
   create_table "reactions", id: :uuid, force: :cascade do |t|
     t.uuid "account_id", null: false
-    t.uuid "comment_id", null: false
     t.string "content", limit: 16, null: false
     t.datetime "created_at", null: false
+    t.uuid "reactable_id", null: false
+    t.string "reactable_type", limit: 255, null: false
     t.uuid "reacter_id", null: false
     t.datetime "updated_at", null: false
     t.index ["account_id"], name: "index_reactions_on_account_id"
-    t.index ["comment_id"], name: "index_reactions_on_comment_id"
+    t.index ["reactable_type", "reactable_id"], name: "index_reactions_on_reactable_type_and_reactable_id"
     t.index ["reacter_id"], name: "index_reactions_on_reacter_id"
   end
 

test/fixtures/reactions.yml

@@ -2,12 +2,12 @@ kevin:
   id: <%= ActiveRecord::FixtureSet.identify("kevin_reaction", :uuid) %>
   account: 37s_uuid
   content: "👍"
-  comment: logo_agreement_jz_uuid
+  reactable: logo_agreement_jz_uuid (Comment)
   reacter: kevin_uuid
 
 david:
   id: <%= ActiveRecord::FixtureSet.identify("david_reaction", :uuid) %>
   account: 37s_uuid
   content: "👍"
-  comment: logo_agreement_jz_uuid
+  reactable: logo_agreement_jz_uuid (Comment)
   reacter: david_uuid