Add ability to search for a collection by URL (#38588)

app/models/search.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 class Search < ActiveModelSerializers::Model
-  attributes :accounts, :statuses, :hashtags
+  attributes :accounts, :statuses, :hashtags, :collections
 end

app/serializers/rest/search_serializer.rb

@@ -4,4 +4,5 @@ class REST::SearchSerializer < ActiveModel::Serializer
   has_many :accounts, serializer: REST::AccountSerializer
   has_many :statuses, serializer: REST::StatusSerializer
   has_many :hashtags, serializer: REST::TagSerializer
+  has_many :collections, serializer: REST::CollectionSerializer
 end

app/services/activitypub/fetch_remote_featured_collection_service.rb

@@ -3,8 +3,12 @@
 class ActivityPub::FetchRemoteFeaturedCollectionService < BaseService
   include JsonLdHelper
 
-  def call(uri, request_id: nil, on_behalf_of: nil)
-    json = fetch_resource(uri, true, on_behalf_of)
+  def call(uri, request_id: nil, prefetched_body: nil, on_behalf_of: nil)
+    json = if prefetched_body.nil?
+             fetch_resource(uri, true, on_behalf_of)
+           else
+             body_to_json(prefetched_body, compare_id: uri)
+           end
 
     return unless supported_context?(json)
     return unless json['type'] == 'FeaturedCollection'

app/services/fetch_resource_service.rb

@@ -63,7 +63,7 @@ class FetchResourceService < BaseService
   end
 
   def expected_type?(json)
-    equals_or_includes_any?(json['type'], ActivityPub::Activity::Create::SUPPORTED_TYPES + ActivityPub::Activity::Create::CONVERTED_TYPES)
+    equals_or_includes_any?(json['type'], ActivityPub::Activity::Create::SUPPORTED_TYPES + ActivityPub::Activity::Create::CONVERTED_TYPES + %w(FeaturedCollection))
   end
 
   def process_html(response)

app/services/resolve_url_service.rb

@@ -28,6 +28,10 @@ class ResolveURLService < BaseService
       status = FetchRemoteStatusService.new.call(resource_url, prefetched_body: body)
       authorize_with @on_behalf_of, status, :show? unless status.nil?
       status
+    elsif type == 'FeaturedCollection' && Mastodon::Feature.collections_enabled?
+      collection = ActivityPub::FetchRemoteFeaturedCollectionService.new.call(resource_url, prefetched_body: body)
+      authorize_with @on_behalf_of, collection, :show? unless collection.nil?
+      collection
     end
   end
 
@@ -111,9 +115,21 @@ class ResolveURLService < BaseService
 
         Account.find_remote(username, domain)
       end
+    when 'collections'
+      return unless recognized_params[:action] == 'show'
+
+      check_collection(Collection.find_by(id: recognized_params[:id]))
     end
   end
 
+  def check_collection(collection)
+    return if collection.nil?
+
+    authorize_with @on_behalf_of, collection, :show?
+  rescue Mastodon::NotPermittedError
+    nil
+  end
+
   def check_local_status(status)
     return if status.nil?
 

app/services/search_service.rb

@@ -64,7 +64,7 @@ class SearchService < BaseService
   end
 
   def default_results
-    { accounts: [], hashtags: [], statuses: [] }
+    { accounts: [], hashtags: [], statuses: [], collections: [] }
   end
 
   def url_query?

spec/services/resolve_url_service_spec.rb

@@ -30,6 +30,49 @@ RSpec.describe ResolveURLService do
       expect(subject.call(url)).to eq known_account
     end
 
+    context 'when searching for a remote collection', feature: :collections do
+      let(:account) { Fabricate(:account) }
+      let(:collection_account) { Fabricate(:account, domain: 'example.com', protocol: :activitypub) }
+
+      let(:uri) { 'https://example.com/featured_collections/1' }
+
+      let(:payload) do
+        {
+          '@context' => 'https://www.w3.org/ns/activitystreams',
+          'id' => uri,
+          'type' => 'FeaturedCollection',
+          'name' => 'Incredible people',
+          'summary' => 'These are really amazing',
+          'attributedTo' => collection_account.uri,
+          'sensitive' => false,
+          'discoverable' => true,
+          'totalItems' => 0,
+        }
+      end
+
+      before do
+        stub_request(:get, uri).to_return(status: 200, body: payload.to_json, headers: { 'Content-Type': 'application/activity+json' })
+      end
+
+      it 'returns the collection' do
+        expect(subject.call(uri, on_behalf_of: account))
+          .to be_a(Collection)
+          .and have_attributes(
+            uri: uri
+          )
+      end
+    end
+
+    context 'when searching for a local collection', feature: :collections do
+      let(:account) { Fabricate(:account) }
+      let(:collection) { Fabricate(:collection) }
+
+      it 'returns the collection' do
+        expect(subject.call(ActivityPub::TagManager.instance.uri_for(collection), on_behalf_of: account))
+          .to eq(collection)
+      end
+    end
+
     context 'when searching for a remote private status' do
       let(:account)  { Fabricate(:account) }
       let(:poster)   { Fabricate(:account, domain: 'example.com') }

spec/services/search_service_spec.rb

@@ -86,6 +86,6 @@ RSpec.describe SearchService do
   end
 
   def empty_results
-    { accounts: [], hashtags: [], statuses: [] }
+    { accounts: [], hashtags: [], statuses: [], collections: [] }
   end
 end