Add featured hashtags as an ActivityPub collection

app/controllers/activitypub/collections_controller.rb

@@ -12,25 +12,17 @@ class ActivityPub::CollectionsController < ActivityPub::BaseController
 
   def show
     expires_in 3.minutes, public: public_fetch_mode?
-    render_with_cache json: collection_presenter, content_type: 'application/activity+json', serializer: ActivityPub::CollectionSerializer, adapter: ActivityPub::Adapter, skip_activities: true
+    render_with_cache json: collection_presenter, content_type: 'application/activity+json', serializer: ActivityPub::CollectionSerializer, adapter: ActivityPub::Adapter
   end
 
   private
 
   def set_items
     case params[:id]
     when 'featured'
-      @items = begin
-        # Because in public fetch mode we cache the response, there would be no
-        # benefit from performing the check below, since a blocked account or domain
-        # would likely be served the cache from the reverse proxy anyway
-
-        if authorized_fetch_mode? && !signed_request_account.nil? && (@account.blocking?(signed_request_account) || (!signed_request_account.domain.nil? && @account.domain_blocking?(signed_request_account.domain)))
-          []
-        else
-          cache_collection(@account.pinned_statuses, Status)
-        end
-      end
+      @items = for_signed_account { cache_collection(@account.pinned_statuses, Status) }
+    when 'tags'
+      @items = for_signed_account { @account.featured_tags }
     when 'devices'
       @items = @account.devices
     else
@@ -40,7 +32,7 @@ def set_items
 
   def set_size
     case params[:id]
-    when 'featured', 'devices'
+    when 'featured', 'devices', 'tags'
       @size = @items.size
     else
       not_found
@@ -51,7 +43,7 @@ def set_type
     case params[:id]
     when 'featured'
       @type = :ordered
-    when 'devices'
+    when 'devices', 'tags'
       @type = :unordered
     else
       not_found
@@ -66,4 +58,16 @@ def collection_presenter
       items: @items
     )
   end
+
+  def for_signed_account
+    # Because in public fetch mode we cache the response, there would be no
+    # benefit from performing the check below, since a blocked account or domain
+    # would likely be served the cache from the reverse proxy anyway
+
+    if authorized_fetch_mode? && !signed_request_account.nil? && (@account.blocking?(signed_request_account) || (!signed_request_account.domain.nil? && @account.domain_blocking?(signed_request_account.domain)))
+      []
+    else
+      yield
+    end
+  end
 end

app/lib/activitypub/adapter.rb

@@ -13,7 +13,7 @@ class ActivityPub::Adapter < ActiveModelSerializers::Adapter::Base
     moved_to: { 'movedTo' => { '@id' => 'as:movedTo', '@type' => '@id' } },
     also_known_as: { 'alsoKnownAs' => { '@id' => 'as:alsoKnownAs', '@type' => '@id' } },
     emoji: { 'toot' => 'http://joinmastodon.org/ns#', 'Emoji' => 'toot:Emoji' },
-    featured: { 'toot' => 'http://joinmastodon.org/ns#', 'featured' => { '@id' => 'toot:featured', '@type' => '@id' } },
+    featured: { 'toot' => 'http://joinmastodon.org/ns#', 'featured' => { '@id' => 'toot:featured', '@type' => '@id' }, 'featuredTags' => { '@id' => 'toot:featuredTags', '@type' => '@id' } },
     property_value: { 'schema' => 'http://schema.org#', 'PropertyValue' => 'schema:PropertyValue', 'value' => 'schema:value' },
     atom_uri: { 'ostatus' => 'http://ostatus.org#', 'atomUri' => 'ostatus:atomUri' },
     conversation: { 'ostatus' => 'http://ostatus.org#', 'inReplyToAtomUri' => 'ostatus:inReplyToAtomUri', 'conversation' => 'ostatus:conversation' },

app/serializers/activitypub/actor_serializer.rb

@@ -10,7 +10,7 @@ class ActivityPub::ActorSerializer < ActivityPub::Serializer
                      :discoverable, :olm
 
   attributes :id, :type, :following, :followers,
-             :inbox, :outbox, :featured,
+             :inbox, :outbox, :featured, :featured_tags,
              :preferred_username, :name, :summary,
              :url, :manually_approves_followers,
              :discoverable
@@ -81,6 +81,10 @@ def featured
     account_collection_url(object, :featured)
   end
 
+  def featured_tags
+    account_collection_url(object, :tags)
+  end
+
   def endpoints
     object
   end

app/serializers/activitypub/collection_serializer.rb

@@ -16,6 +16,8 @@ def self.serializer_for(model, options)
       ActivityPub::NoteSerializer
     when 'Device'
       ActivityPub::DeviceSerializer
+    when 'FeaturedTag'
+      ActivityPub::HashtagSerializer
     when 'ActivityPub::CollectionPresenter'
       ActivityPub::CollectionSerializer
     when 'String'

app/serializers/activitypub/hashtag_serializer.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class ActivityPub::HashtagSerializer < ActivityPub::Serializer
+  include RoutingHelper
+
+  attributes :type, :href, :name
+
+  def type
+    'Hashtag'
+  end
+
+  def name
+    "##{object.name}"
+  end
+
+  def href
+    if object.class.name == 'FeaturedTag'
+      short_account_tag_url(object.account, object.tag)
+    else
+      tag_url(object)
+    end
+  end
+end