User settings mutation (mastodon#2270)

* Add user spec for settings, highlight global default mutation issue

* Fix mutation issue caused by settings/preferences spec

spec/controllers/settings/preferences_controller_spec.rb

@@ -24,8 +24,8 @@
 
     it 'updates user settings' do
       user.settings['boost_modal'] = false
-      user.settings['notification_emails']['follow'] = false
-      user.settings['interactions']['must_be_follower'] = true
+      user.settings['notification_emails'] = user.settings['notification_emails'].merge('follow' => false)
+      user.settings['interactions'] = user.settings['interactions'].merge('must_be_follower' => true)
 
       put :update, params: {
         user: {

spec/models/user_spec.rb

@@ -24,6 +24,37 @@
     end
   end
 
+  describe 'settings' do
+    it 'inherits default settings from default yml' do
+      expect(Setting.boost_modal).to eq false
+      expect(Setting.interactions['must_be_follower']).to eq false
+
+      user = User.new
+      expect(user.settings.boost_modal).to eq false
+      expect(user.settings.interactions['must_be_follower']).to eq false
+    end
+
+    it 'can update settings' do
+      user = Fabricate(:user)
+      expect(user.settings['interactions']['must_be_follower']).to eq false
+      user.settings['interactions'] = user.settings['interactions'].merge('must_be_follower' => true)
+      user.reload
+
+      expect(user.settings['interactions']['must_be_follower']).to eq true
+    end
+
+    xit 'does not mutate defaults via the cache' do
+      user = Fabricate(:user)
+      user.settings['interactions']['must_be_follower'] = true
+      # TODO
+      # This mutates the global settings default such that future user
+      # instances will inherit the incorrect starting values
+
+      other = Fabricate(:user)
+      expect(other.settings['interactions']['must_be_follower']).to eq false
+    end
+  end
+
   describe 'scopes' do
     describe 'recent' do
       it 'returns an array of recent users ordered by id' do