Add language attribute to collections (#37549)

app/controllers/api/v1_alpha/collections_controller.rb

@@ -81,11 +81,11 @@ class Api::V1Alpha::CollectionsController < Api::BaseController
   end
 
   def collection_creation_params
-    params.permit(:name, :description, :sensitive, :discoverable, :tag_name, account_ids: [])
+    params.permit(:name, :description, :language, :sensitive, :discoverable, :tag_name, account_ids: [])
   end
 
   def collection_update_params
-    params.permit(:name, :description, :sensitive, :discoverable, :tag_name)
+    params.permit(:name, :description, :language, :sensitive, :discoverable, :tag_name)
   end
 
   def check_feature_enabled

app/models/collection.rb

@@ -8,6 +8,7 @@
 #  description              :text             not null
 #  discoverable             :boolean          not null
 #  item_count               :integer          default(0), not null
+#  language                 :string
 #  local                    :boolean          not null
 #  name                     :string           not null
 #  original_number_of_items :integer
@@ -36,6 +37,7 @@ class Collection < ApplicationRecord
             presence: true,
             numericality: { greater_than_or_equal: 0 },
             if: :remote?
+  validates :language, language: { if: :local?, allow_nil: true }
   validate :tag_is_usable
   validate :items_do_not_exceed_limit
 

app/serializers/activitypub/featured_collection_serializer.rb

@@ -17,9 +17,12 @@ class ActivityPub::FeaturedCollectionSerializer < ActivityPub::Serializer
     end
   end
 
-  attributes :id, :type, :total_items, :name, :summary, :attributed_to,
+  attributes :id, :type, :total_items, :name, :attributed_to,
              :sensitive, :discoverable, :published, :updated
 
+  attribute :summary, unless: :language_present?
+  attribute :summary_map, if: :language_present?
+
   has_one :tag, key: :topic, serializer: ActivityPub::NoteSerializer::TagSerializer
 
   has_many :collection_items, key: :ordered_items, serializer: FeaturedItemSerializer
@@ -36,6 +39,10 @@ class ActivityPub::FeaturedCollectionSerializer < ActivityPub::Serializer
     object.description
   end
 
+  def summary_map
+    { object.language => object.description }
+  end
+
   def attributed_to
     ActivityPub::TagManager.instance.uri_for(object.account)
   end
@@ -51,4 +58,8 @@ class ActivityPub::FeaturedCollectionSerializer < ActivityPub::Serializer
   def updated
     object.updated_at.iso8601
   end
+
+  def language_present?
+    object.language.present?
+  end
 end

app/serializers/rest/base_collection_serializer.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 class REST::BaseCollectionSerializer < ActiveModel::Serializer
-  attributes :id, :uri, :name, :description, :local, :sensitive,
+  attributes :id, :uri, :name, :description, :language, :local, :sensitive,
              :discoverable, :item_count, :created_at, :updated_at
 
   belongs_to :tag, serializer: REST::StatusSerializer::TagSerializer

db/migrate/20260119153538_add_language_to_collections.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddLanguageToCollections < ActiveRecord::Migration[8.0]
+  def change
+    add_column :collections, :language, :string
+  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[8.0].define(version: 2026_01_15_153219) do
+ActiveRecord::Schema[8.0].define(version: 2026_01_19_153538) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_catalog.plpgsql"
 
@@ -382,6 +382,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_01_15_153219) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.integer "item_count", default: 0, null: false
+    t.string "language"
     t.index ["account_id"], name: "index_collections_on_account_id"
     t.index ["tag_id"], name: "index_collections_on_tag_id"
   end

spec/models/collection_spec.rb

@@ -16,12 +16,18 @@ RSpec.describe Collection do
 
     it { is_expected.to_not allow_value(nil).for(:discoverable) }
 
+    it { is_expected.to allow_value('en').for(:language) }
+
+    it { is_expected.to_not allow_value('randomstuff').for(:language) }
+
     context 'when collection is remote' do
       subject { Fabricate.build :collection, local: false }
 
       it { is_expected.to validate_presence_of(:uri) }
 
       it { is_expected.to validate_presence_of(:original_number_of_items) }
+
+      it { is_expected.to allow_value('randomstuff').for(:language) }
     end
 
     context 'when using a hashtag as category' do

spec/requests/api/v1_alpha/collections_spec.rb

@@ -115,6 +115,7 @@ RSpec.describe 'Api::V1Alpha::Collections', feature: :collections do
         {
           name: 'Low-traffic bots',
           description: 'Really nice bots, please follow',
+          language: 'en',
           sensitive: '0',
           discoverable: '1',
         }

spec/serializers/activitypub/featured_collection_serializer_spec.rb

@@ -45,4 +45,20 @@ RSpec.describe ActivityPub::FeaturedCollectionSerializer do
       'updated' => match_api_datetime_format,
     })
   end
+
+  context 'when a language is set' do
+    before do
+      collection.language = 'en'
+    end
+
+    it 'uses "summaryMap" to include the language' do
+      expect(subject).to include({
+        'summaryMap' => {
+          'en' => 'These are really amazing',
+        },
+      })
+
+      expect(subject).to_not have_key('summary')
+    end
+  end
 end

spec/serializers/rest/collection_serializer_spec.rb

@@ -18,6 +18,7 @@ RSpec.describe REST::CollectionSerializer do
               id: 2342,
               name: 'Exquisite follows',
               description: 'Always worth a follow',
+              language: 'en',
               local: true,
               sensitive: true,
               discoverable: false,
@@ -31,6 +32,7 @@ RSpec.describe REST::CollectionSerializer do
         'id' => '2342',
         'name' => 'Exquisite follows',
         'description' => 'Always worth a follow',
+        'language' => 'en',
         'local' => true,
         'sensitive' => true,
         'discoverable' => false,