Fix anonymous visitors getting a session cookie on first visit (#24584)

spec/requests/anonymous_cookies_spec.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+context 'when visited anonymously' do
+  around do |example|
+    old = ActionController::Base.allow_forgery_protection
+    ActionController::Base.allow_forgery_protection = true
+
+    example.run
+
+    ActionController::Base.allow_forgery_protection = old
+  end
+
+  describe 'account pages' do
+    it 'do not set cookies' do
+      alice = Fabricate(:account, username: 'alice', display_name: 'Alice')
+      _status = Fabricate(:status, account: alice, text: 'Hello World')
+
+      get '/@alice'
+
+      expect(response.cookies).to be_empty
+    end
+  end
+
+  describe 'status pages' do
+    it 'do not set cookies' do
+      alice = Fabricate(:account, username: 'alice', display_name: 'Alice')
+      status = Fabricate(:status, account: alice, text: 'Hello World')
+
+      get short_account_status_url(alice, status)
+
+      expect(response.cookies).to be_empty
+    end
+  end
+
+  describe 'the /about page' do
+    it 'does not set cookies' do
+      get '/about'
+
+      expect(response.cookies).to be_empty
+    end
+  end
+end