Fix error and incorrect URLs in /api/v1/accounts/:id/featured_tags for remote accounts (#27459)

app/serializers/rest/featured_tag_serializer.rb

@@ -10,7 +10,9 @@ class REST::FeaturedTagSerializer < ActiveModel::Serializer
   end
 
   def url
-    short_account_tag_url(object.account, object.tag)
+    # The path is hardcoded because we have to deal with both local and
+    # remote users, which are different routes
+    account_with_domain_url(object.account, "tagged/#{object.tag.to_param}")
   end
 
   def name

config/routes.rb

@@ -126,7 +126,7 @@ Rails.application.routes.draw do
     get '/@:account_username/:id/embed', to: 'statuses#embed', as: :embed_short_account_status
   end
 
-  get '/@:username_with_domain/(*any)', to: 'home#index', constraints: { username_with_domain: /([^\/])+?/ }, format: false
+  get '/@:username_with_domain/(*any)', to: 'home#index', constraints: { username_with_domain: %r{([^/])+?} }, as: :account_with_domain, format: false
   get '/settings', to: redirect('/settings/profile')
 
   namespace :settings do

spec/requests/api/v1/accounts/featured_tags_spec.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'account featured tags API' do
+  let(:user)     { Fabricate(:user) }
+  let(:token)    { Fabricate(:accessible_access_token, resource_owner_id: user.id, scopes: scopes) }
+  let(:scopes)   { 'read:accounts' }
+  let(:headers)  { { 'Authorization' => "Bearer #{token.token}" } }
+  let(:account)  { Fabricate(:account) }
+
+  describe 'GET /api/v1/accounts/:id/featured_tags' do
+    subject do
+      get "/api/v1/accounts/#{account.id}/featured_tags", headers: headers
+    end
+
+    before do
+      account.featured_tags.create!(name: 'foo')
+      account.featured_tags.create!(name: 'bar')
+    end
+
+    it 'returns the expected tags', :aggregate_failures do
+      subject
+
+      expect(response).to have_http_status(200)
+      expect(body_as_json).to contain_exactly(a_hash_including({
+        name: 'bar',
+        url: "https://cb6e6126.ngrok.io/@#{account.username}/tagged/bar",
+      }), a_hash_including({
+        name: 'foo',
+        url: "https://cb6e6126.ngrok.io/@#{account.username}/tagged/foo",
+      }))
+    end
+
+    context 'when the account is remote' do
+      it 'returns the expected tags', :aggregate_failures do
+        subject
+
+        expect(response).to have_http_status(200)
+        expect(body_as_json).to contain_exactly(a_hash_including({
+          name: 'bar',
+          url: "https://cb6e6126.ngrok.io/@#{account.pretty_acct}/tagged/bar",
+        }), a_hash_including({
+          name: 'foo',
+          url: "https://cb6e6126.ngrok.io/@#{account.pretty_acct}/tagged/foo",
+        }))
+      end
+    end
+  end
+end