Add attachment publication support

Author: angusmcleod

app/models/discourse_activity_pub_object.rb

@@ -159,6 +159,10 @@ def attributed_to
     end
   end
 
+  def attachment
+    self.attachments
+  end
+
   def likes_collection
     @likes_collection ||=
       begin

app/serializers/discourse_activity_pub/ap/object/article_serializer.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 class DiscourseActivityPub::AP::Object::ArticleSerializer < DiscourseActivityPub::AP::ObjectSerializer
-  attributes :content, :inReplyTo, :url, :updated
+  attributes :content, :inReplyTo, :url, :updated, :attachment
 
   def inReplyTo
     object.in_reply_to
@@ -18,4 +18,12 @@ def include_content?
   def deleted?
     !object.stored.model || object.stored.model.trashed?
   end
+
+  def attachment
+    object.attachment.map(&:json)
+  end
+
+  def include_attachment?
+    object.attachment.present?
+  end
 end

app/serializers/discourse_activity_pub/ap/object/document_serializer.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class DiscourseActivityPub::AP::Object::DocumentSerializer < DiscourseActivityPub::AP::ObjectSerializer
+  attributes :media_type
+end

app/serializers/discourse_activity_pub/ap/object/image_serializer.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class DiscourseActivityPub::AP::Object::ImageSerializer < DiscourseActivityPub::AP::ObjectSerializer
+  attributes :media_type
+end

app/serializers/discourse_activity_pub/ap/object/note_serializer.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 class DiscourseActivityPub::AP::Object::NoteSerializer < DiscourseActivityPub::AP::ObjectSerializer
-  attributes :content, :inReplyTo, :context
+  attributes :content, :inReplyTo, :context, :attachment
 
   def content
     content = object.content
@@ -30,4 +30,12 @@ def include_content?
   def deleted?
     !object.stored.model || object.stored.model.trashed?
   end
+
+  def attachment
+    object.attachment.map(&:json)
+  end
+
+  def include_attachment?
+    object.attachment.present?
+  end
 end

app/serializers/discourse_activity_pub/ap/object_serializer.rb

@@ -21,6 +21,7 @@ def attributes(*args)
   end
 
   def include_id?
+    return false if object.attachment?
     object.id.present?
   end
 

lib/discourse_activity_pub/ap/object.rb

@@ -7,6 +7,8 @@ class Object
       include HasErrors
       include Handlers
 
+      ATTACHMENT_TYPES = %w[Image Document]
+
       attr_writer :json
       attr_writer :attributed_to
       attr_writer :context
@@ -50,6 +52,10 @@ def actor?
         base_type == "Actor"
       end
 
+      def attachment?
+        ATTACHMENT_TYPES.include?(type)
+      end
+
       def url
         if stored
           stored.respond_to?(:url) && stored&.url
@@ -118,12 +124,10 @@ def delivered_to
         @delivered_to ||= []
       end
 
-      def media_type
-        json[:mediaType] if json.present?
-      end
-
       def attachment
-        if json.present? && json[:attachment].present?
+        if stored.respond_to?(:attachment)
+          @attachment ||= (stored.attachment || []).map { |a| a.ap }
+        elsif json.present? && json[:attachment].present?
           json[:attachment].each_with_object([]) do |attachment_json, result|
             obj = AP::Object.factory(attachment_json)
             result << obj if obj.present?

lib/discourse_activity_pub/ap/object/document.rb

@@ -7,6 +7,14 @@ def type
           "Document"
         end
 
+        def media_type
+          if stored && stored.respond_to?(:media_type)
+            stored.media_type
+          elsif json
+            json[:mediaType]
+          end
+        end
+
         def can_belong_to
           %i[remote]
         end

lib/discourse_activity_pub/ap/object/image.rb

@@ -7,6 +7,14 @@ def type
           "Image"
         end
 
+        def media_type
+          if stored && stored.respond_to?(:media_type)
+            stored.media_type
+          elsif json
+            json[:mediaType]
+          end
+        end
+
         def can_belong_to
           %i[remote]
         end

plugin.rb

@@ -140,6 +140,8 @@
   require_relative "app/serializers/discourse_activity_pub/ap/actor/person_serializer"
   require_relative "app/serializers/discourse_activity_pub/ap/object/note_serializer"
   require_relative "app/serializers/discourse_activity_pub/ap/object/article_serializer"
+  require_relative "app/serializers/discourse_activity_pub/ap/object/image_serializer"
+  require_relative "app/serializers/discourse_activity_pub/ap/object/document_serializer"
   require_relative "app/serializers/discourse_activity_pub/ap/collection_serializer"
   require_relative "app/serializers/discourse_activity_pub/ap/collection/ordered_collection_serializer"
   require_relative "app/serializers/discourse_activity_pub/about_serializer"
@@ -1185,25 +1187,28 @@
                   )
           end
 
-          if object.attachment.present?
-            object.attachment.each do |attachment|
-              # Some platforms (e.g. Mastodon) put attachment url media types on the attachment itself,
-              # instead of on a Link object in the url attribute. Technically this violates the specification,
-              # but we need to support it nevertheless. See further https://www.w3.org/TR/activitystreams-vocabulary/#dfn-mediatype
-              media_type = attachment.url.media_type || attachment.media_type
-              name = attachment.url.name || attachment.name
-
-              begin
-                DiscourseActivityPubAttachment.create(
-                  object_id: object.stored.id,
-                  object_type: "DiscourseActivityPubObject",
-                  ap_type: attachment.type,
-                  url: attachment.url.href,
-                  name: name,
-                  media_type: media_type,
-                )
-              rescue ActiveRecord::RecordInvalid => error
-                # fail silently if an attachment does not validate
+          if object.json[:attachment].present?
+            object.json[:attachment].each do |json|
+              attachment = DiscourseActivityPub::AP::Object.factory(json)
+              if attachment
+                # Some platforms (e.g. Mastodon) put attachment url media types on the attachment itself,
+                # instead of on a Link object in the url attribute. Technically this violates the specification,
+                # but we need to support it nevertheless. See further https://www.w3.org/TR/activitystreams-vocabulary/#dfn-mediatype
+                media_type = attachment.url.media_type || attachment.media_type
+                name = attachment.url.name || attachment.name
+
+                begin
+                  DiscourseActivityPubAttachment.create(
+                    object_id: object.stored.id,
+                    object_type: "DiscourseActivityPubObject",
+                    ap_type: attachment.type,
+                    url: attachment.url.href,
+                    name: name,
+                    media_type: media_type,
+                  )
+                rescue ActiveRecord::RecordInvalid => error
+                  # fail silently if an attachment does not validate
+                end
               end
             end
           end

spec/fabricators/discourse_activity_pub_attachment_fabricator.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+Fabricator(:discourse_activity_pub_attachment) do
+  ap_type { "Image" }
+  media_type { "image/png" }
+
+  before_create do |object|
+    filename = "#{SecureRandom.hex(8)}-image"
+    object.url = "https://local.com/attachment/image/#{filename}.png"
+    object.name = filename
+  end
+end

spec/jobs/discourse_activity_pub_deliver_spec.rb

@@ -335,6 +335,29 @@ def find_announce
           end
         end
       end
+
+      context "when object has attachments" do
+        let!(:topic) { Fabricate(:topic, category: group.model) }
+        let!(:post) { Fabricate(:post, topic: topic) }
+        let!(:note) { Fabricate(:discourse_activity_pub_object_note, local: true, model: post) }
+        let!(:attachment1) { Fabricate(:discourse_activity_pub_attachment, object: note) }
+        let!(:attachment2) { Fabricate(:discourse_activity_pub_attachment, object: note) }
+        let!(:activity) do
+          Fabricate(:discourse_activity_pub_activity_create, object: note, actor: group)
+        end
+
+        it "publishes the attachments" do
+          json = published_json(activity)
+          expect(json[:object][:attachment].size).to eq(2)
+          expect(json[:object][:attachment].first[:url]).to eq(attachment1.url)
+          expect(json[:object][:attachment].second[:url]).to eq(attachment2.url)
+        end
+
+        it "performs the right request" do
+          expect_request(body: published_json(activity), actor_id: group.id, uri: person.inbox)
+          execute_job(object_id: activity.id, from_actor_id: activity.actor.id)
+        end
+      end
     end
   end
 end