Fix compatibility with Friendica regarding pinned posts (#18254)

* Fix multiple database queries when fetching pinned posts for remote account

* Fix compatibility with Friendica regarding pinned posts

Fixes #18066

* Add tests

2 files changed, 146 insertions, 11 deletions

diff --git a/app/services/activitypub/fetch_featured_collection_service.rb b/app/services/activitypub/fetch_featured_collection_service.rb
index 07a9fe039..e62470f70 100644
--- a/app/services/activitypub/fetch_featured_collection_service.rb
+++ b/app/services/activitypub/fetch_featured_collection_service.rb
@@ -7,19 +7,33 @@ class ActivityPub::FetchFeaturedCollectionService < BaseService
     return if account.featured_collection_url.blank? || account.suspended? || account.local?
 
     @account = account
-    @json    = fetch_resource(@account.featured_collection_url, true)
+    @json    = fetch_resource(@account.featured_collection_url, true, local_follower)
 
-    return unless supported_context?
+    return unless supported_context?(@json)
 
-    case @json['type']
+    process_items(collection_items(@json))
+  end
+
+  private
+
+  def collection_items(collection)
+    collection = fetch_collection(collection['first']) if collection['first'].present?
+    return unless collection.is_a?(Hash)
+
+    case collection['type']
     when 'Collection', 'CollectionPage'
-      process_items @json['items']
+      collection['items']
     when 'OrderedCollection', 'OrderedCollectionPage'
-      process_items @json['orderedItems']
+      collection['orderedItems']
     end
   end
 
-  private
+  def fetch_collection(collection_or_uri)
+    return collection_or_uri if collection_or_uri.is_a?(Hash)
+    return if invalid_origin?(collection_or_uri)
+
+    fetch_resource_without_id_validation(collection_or_uri, nil, true, local_follower)
+  end
 
   def process_items(items)
     status_ids = items.filter_map do |item|
@@ -53,11 +67,9 @@ class ActivityPub::FetchFeaturedCollectionService < BaseService
     end
   end
 
-  def supported_context?
-    super(@json)
-  end
-
   def local_follower
-    @local_follower ||= @account.followers.local.without_suspended.first
+    return @local_follower if defined?(@local_follower)
+
+    @local_follower = @account.followers.local.without_suspended.first
   end
 end
diff --git a/spec/services/activitypub/fetch_featured_collection_service_spec.rb b/spec/services/activitypub/fetch_featured_collection_service_spec.rb
new file mode 100644
index 000000000..f552b9dc0
--- /dev/null
+++ b/spec/services/activitypub/fetch_featured_collection_service_spec.rb
@@ -0,0 +1,123 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::FetchFeaturedCollectionService, type: :service do
+  let(:actor) { Fabricate(:account, domain: 'example.com', uri: 'https://example.com/account', featured_collection_url: 'https://example.com/account/pinned') }
+
+  let!(:known_status) { Fabricate(:status, account: actor, uri: 'https://example.com/account/pinned/1') }
+
+  let(:status_json_1) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      type: 'Note',
+      id: 'https://example.com/account/pinned/1',
+      content: 'foo',
+      attributedTo: actor.uri,
+      to: 'https://www.w3.org/ns/activitystreams#Public',
+    }
+  end
+
+  let(:status_json_2) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      type: 'Note',
+      id: 'https://example.com/account/pinned/2',
+      content: 'foo',
+      attributedTo: actor.uri,
+      to: 'https://www.w3.org/ns/activitystreams#Public',
+    }
+  end
+
+  let(:status_json_4) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      type: 'Note',
+      id: 'https://example.com/account/pinned/4',
+      content: 'foo',
+      attributedTo: actor.uri,
+      to: 'https://www.w3.org/ns/activitystreams#Public',
+    }
+  end
+
+  let(:items) do
+    [
+      'https://example.com/account/pinned/1', # known
+      status_json_2, # unknown inlined
+      'https://example.com/account/pinned/3', # unknown unreachable
+      'https://example.com/account/pinned/4', # unknown reachable
+    ]
+  end
+
+  let(:payload) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      type: 'Collection',
+      id: actor.featured_collection_url,
+      items: items,
+    }.with_indifferent_access
+  end
+
+  subject { described_class.new }
+
+  shared_examples 'sets pinned posts' do
+    before do
+      stub_request(:get, 'https://example.com/account/pinned/1').to_return(status: 200, body: Oj.dump(status_json_1))
+      stub_request(:get, 'https://example.com/account/pinned/2').to_return(status: 200, body: Oj.dump(status_json_2))
+      stub_request(:get, 'https://example.com/account/pinned/3').to_return(status: 404)
+      stub_request(:get, 'https://example.com/account/pinned/4').to_return(status: 200, body: Oj.dump(status_json_4))
+
+      subject.call(actor)
+    end
+
+    it 'sets expected posts as pinned posts' do
+      expect(actor.pinned_statuses.pluck(:uri)).to match_array ['https://example.com/account/pinned/1', 'https://example.com/account/pinned/2', 'https://example.com/account/pinned/4']
+    end
+  end
+
+  describe '#call' do
+    context 'when the endpoint is a Collection' do
+      before do
+        stub_request(:get, actor.featured_collection_url).to_return(status: 200, body: Oj.dump(payload))
+      end
+
+      it_behaves_like 'sets pinned posts'
+    end
+
+    context 'when the endpoint is an OrderedCollection' do
+      let(:payload) do
+        {
+          '@context': 'https://www.w3.org/ns/activitystreams',
+          type: 'OrderedCollection',
+          id: actor.featured_collection_url,
+          orderedItems: items,
+        }.with_indifferent_access
+      end
+
+      before do
+        stub_request(:get, actor.featured_collection_url).to_return(status: 200, body: Oj.dump(payload))
+      end
+
+      it_behaves_like 'sets pinned posts'
+    end
+
+    context 'when the endpoint is a paginated Collection' do
+      let(:payload) do
+        {
+          '@context': 'https://www.w3.org/ns/activitystreams',
+          type: 'Collection',
+          id: actor.featured_collection_url,
+          first: {
+            type: 'CollectionPage',
+            partOf: actor.featured_collection_url,
+            items: items,
+          }
+        }.with_indifferent_access
+      end
+
+      before do
+        stub_request(:get, actor.featured_collection_url).to_return(status: 200, body: Oj.dump(payload))
+      end
+
+      it_behaves_like 'sets pinned posts'
+    end
+  end
+end