Fix validation error in SynchronizeFeaturedTagsCollectionWorker (#20018)

* Fix followers count not being updated when migrating follows

Fixes #19900

* Fix validation error in SynchronizeFeaturedTagsCollectionWorker

Also saves remote user's chosen case for hashtags

* Limit remote featured tags before validation

app/models/featured_tag.rb

@@ -63,6 +63,8 @@ class FeaturedTag < ApplicationRecord
   end
 
   def validate_featured_tags_limit
+    return unless account.local?
+
     errors.add(:base, I18n.t('featured_tags.errors.limit')) if account.featured_tags.count >= LIMIT
   end
 

app/services/activitypub/fetch_featured_tags_collection_service.rb

@@ -51,21 +51,17 @@ class ActivityPub::FetchFeaturedTagsCollectionService < BaseService
   end
 
   def process_items(items)
-    names     = items.filter_map { |item| item['type'] == 'Hashtag' && item['name']&.delete_prefix('#') }.map { |name| HashtagNormalizer.new.normalize(name) }
-    to_remove = []
-    to_add    = names
+    names            = items.filter_map { |item| item['type'] == 'Hashtag' && item['name']&.delete_prefix('#') }.take(FeaturedTag::LIMIT)
+    tags             = names.index_by { |name| HashtagNormalizer.new.normalize(name) }
+    normalized_names = tags.keys
 
-    FeaturedTag.where(account: @account).map(&:name).each do |name|
-      if names.include?(name)
-        to_add.delete(name)
-      else
-        to_remove << name
-      end
+    FeaturedTag.includes(:tag).references(:tag).where(account: @account).where.not(tag: { name: normalized_names }).delete_all
+
+    FeaturedTag.includes(:tag).references(:tag).where(account: @account, tag: { name: normalized_names }).each do |featured_tag|
+      featured_tag.update(name: tags.delete(featured_tag.tag.name))
     end
 
-    FeaturedTag.includes(:tag).where(account: @account, tags: { name: to_remove }).delete_all unless to_remove.empty?
-
-    to_add.each do |name|
+    tags.each_value do |name|
       FeaturedTag.create!(account: @account, name: name)
     end
   end

spec/services/activitypub/fetch_featured_tags_collection_service_spec.rb

@@ -0,0 +1,95 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::FetchFeaturedTagsCollectionService, type: :service do
+  let(:collection_url) { 'https://example.com/account/tags' }
+  let(:actor) { Fabricate(:account, domain: 'example.com', uri: 'https://example.com/account') }
+
+  let(:items) do
+    [
+      { type: 'Hashtag', href: 'https://example.com/account/tagged/foo', name: 'Foo' },
+      { type: 'Hashtag', href: 'https://example.com/account/tagged/bar', name: 'bar' },
+      { type: 'Hashtag', href: 'https://example.com/account/tagged/baz', name: 'baZ' },
+    ]
+  end
+
+  let(:payload) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      type: 'Collection',
+      id: collection_url,
+      items: items,
+    }.with_indifferent_access
+  end
+
+  subject { described_class.new }
+
+  shared_examples 'sets featured tags' do
+    before do
+      subject.call(actor, collection_url)
+    end
+
+    it 'sets expected tags as pinned tags' do
+      expect(actor.featured_tags.map(&:display_name)).to match_array ['Foo', 'bar', 'baZ']
+    end
+  end
+
+  describe '#call' do
+    context 'when the endpoint is a Collection' do
+      before do
+        stub_request(:get, collection_url).to_return(status: 200, body: Oj.dump(payload))
+      end
+
+      it_behaves_like 'sets featured tags'
+    end
+
+    context 'when the account already has featured tags' do
+      before do
+        stub_request(:get, collection_url).to_return(status: 200, body: Oj.dump(payload))
+
+        actor.featured_tags.create!(name: 'FoO')
+        actor.featured_tags.create!(name: 'baz')
+        actor.featured_tags.create!(name: 'oh').update(name: nil)
+      end
+
+      it_behaves_like 'sets featured tags'
+    end
+
+    context 'when the endpoint is an OrderedCollection' do
+      let(:payload) do
+        {
+          '@context': 'https://www.w3.org/ns/activitystreams',
+          type: 'OrderedCollection',
+          id: collection_url,
+          orderedItems: items,
+        }.with_indifferent_access
+      end
+
+      before do
+        stub_request(:get, collection_url).to_return(status: 200, body: Oj.dump(payload))
+      end
+
+      it_behaves_like 'sets featured tags'
+    end
+
+    context 'when the endpoint is a paginated Collection' do
+      let(:payload) do
+        {
+          '@context': 'https://www.w3.org/ns/activitystreams',
+          type: 'Collection',
+          id: collection_url,
+          first: {
+            type: 'CollectionPage',
+            partOf: collection_url,
+            items: items,
+          }
+        }.with_indifferent_access
+      end
+
+      before do
+        stub_request(:get, collection_url).to_return(status: 200, body: Oj.dump(payload))
+      end
+
+      it_behaves_like 'sets featured tags'
+    end
+  end
+end