Make timestamptz a time zone aware type for Postgres

rails#41395 added support for the `timestamptz` type on the Postgres adapter.

As we found [here](rails#41084 (comment)) this causes issues because in some scenarios the new type is not considered a time zone aware attribute, meaning values of this type in the DB are presented as a `Time`, not an `ActiveSupport::TimeWithZone`.

This PR fixes that by ensuring that `timestamptz` is always a time zone aware type, for Postgres users.

Author: ghiculescu

activerecord/CHANGELOG.md

@@ -1,3 +1,15 @@
+*   Add `timestamptz` as a time zone aware type for PostgreSQL
+
+    This is required for correctly parsing `timestamp with time zone` values in your database.
+
+    If you don't want this, you can opt out by adding this initializer:
+
+    ```ruby
+    ActiveRecord::Base.time_zone_aware_types -= [:timestamptz]
+    ```
+
+    *Alex Ghiculescu*
+    
 *   Add new `ActiveRecord::Base::generates_token_for` API.
 
     Currently, `signed_id` fulfills the role of generating tokens for e.g.

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -1095,5 +1095,6 @@ def decode(value, tuple = nil, field = nil)
         ActiveRecord::Type.register(:vector, OID::Vector, adapter: :postgresql)
         ActiveRecord::Type.register(:xml, OID::Xml, adapter: :postgresql)
     end
+    ActiveSupport.run_load_hooks(:active_record_postgresqladapter, PostgreSQLAdapter)
   end
 end

activerecord/lib/active_record/railtie.rb

@@ -78,6 +78,12 @@ class Railtie < Rails::Railtie # :nodoc:
       end
     end
 
+    initializer "active_record.postgresql_time_zone_aware_types" do
+      ActiveSupport.on_load(:active_record_postgresqladapter) do
+        ActiveRecord::Base.time_zone_aware_types << :timestamptz
+      end
+    end
+
     initializer "active_record.logger" do
       ActiveSupport.on_load(:active_record) { self.logger ||= ::Rails.logger }
     end

activerecord/test/cases/adapters/postgresql/timestamp_test.rb

@@ -18,7 +18,7 @@ class PostgresqlTimestampWithZone < ActiveRecord::Base; end
     PostgresqlTimestampWithZone.delete_all
   end
 
-  def test_timestamp_with_zone_values_with_rails_time_zone_support
+  def test_timestamp_with_zone_values_with_rails_time_zone_support_and_no_time_zone_set
     with_timezone_config default: :utc, aware_attributes: true do
       @connection.reconnect!
 
@@ -45,6 +45,78 @@ def test_timestamp_with_zone_values_without_rails_time_zone_support
   end
 end
 
+class PostgresqlTimestampWithAwareTypesTest < ActiveRecord::PostgreSQLTestCase
+  class PostgresqlTimestampWithZone < ActiveRecord::Base; end
+
+  self.use_transactional_tests = false
+
+  setup do
+    @connection = ActiveRecord::Base.connection
+    @connection.execute("INSERT INTO postgresql_timestamp_with_zones (id, time) VALUES (1, '2010-01-01 10:00:00-1')")
+  end
+
+  teardown do
+    PostgresqlTimestampWithZone.delete_all
+  end
+
+  def test_timestamp_with_zone_values_with_rails_time_zone_support_and_time_zone_set
+    with_timezone_config default: :utc, aware_attributes: true, zone: "Pacific Time (US & Canada)", aware_types: [:timestamptz, :datetime, :time] do
+      @connection.reconnect!
+
+      timestamp = PostgresqlTimestampWithZone.find(1)
+      assert_equal Time.utc(2010, 1, 1, 11, 0, 0), timestamp.time
+      assert_instance_of ActiveSupport::TimeWithZone, timestamp.time
+    end
+  ensure
+    @connection.reconnect!
+  end
+end
+
+class PostgresqlTimestampWithTimeZoneTest < ActiveRecord::PostgreSQLTestCase
+  class PostgresqlTimestampWithZone < ActiveRecord::Base; end
+
+  self.use_transactional_tests = false
+
+  setup do
+    with_postgresql_datetime_type(:timestamptz) do
+      @connection = ActiveRecord::Base.connection
+      @connection.execute("INSERT INTO postgresql_timestamp_with_zones (id, time) VALUES (1, '2010-01-01 10:00:00-1')")
+    end
+  end
+
+  teardown do
+    PostgresqlTimestampWithZone.delete_all
+  end
+
+  def test_timestamp_with_zone_values_with_rails_time_zone_support_and_timestamptz_and_no_time_zone_set
+    with_postgresql_datetime_type(:timestamptz) do
+      with_timezone_config default: :utc, aware_attributes: true, aware_types: [:timestamptz, :datetime, :time] do
+        @connection.reconnect!
+
+        timestamp = PostgresqlTimestampWithZone.find(1)
+        assert_equal Time.utc(2010, 1, 1, 11, 0, 0), timestamp.time
+        assert_instance_of Time, timestamp.time
+      end
+    end
+  ensure
+    @connection.reconnect!
+  end
+
+  def test_timestamp_with_zone_values_with_rails_time_zone_support_and_timestamptz_and_time_zone_set
+    with_postgresql_datetime_type(:timestamptz) do
+      with_timezone_config default: :utc, aware_attributes: true, zone: "Pacific Time (US & Canada)", aware_types: [:timestamptz, :datetime, :time] do
+        @connection.reconnect!
+
+        timestamp = PostgresqlTimestampWithZone.find(1)
+        assert_equal Time.utc(2010, 1, 1, 11, 0, 0), timestamp.time
+        assert_instance_of ActiveSupport::TimeWithZone, timestamp.time
+      end
+    end
+  ensure
+    @connection.reconnect!
+  end
+end
+
 class PostgresqlTimestampFixtureTest < ActiveRecord::PostgreSQLTestCase
   fixtures :topics
 

activerecord/test/cases/helper.rb

@@ -102,6 +102,7 @@ def with_timezone_config(cfg)
 
   old_default_zone = ActiveRecord.default_timezone
   old_awareness = ActiveRecord::Base.time_zone_aware_attributes
+  old_aware_types = ActiveRecord::Base.time_zone_aware_types
   old_zone = Time.zone
 
   if cfg.has_key?(:default)
@@ -110,19 +111,24 @@ def with_timezone_config(cfg)
   if cfg.has_key?(:aware_attributes)
     ActiveRecord::Base.time_zone_aware_attributes = cfg[:aware_attributes]
   end
+  if cfg.has_key?(:aware_types)
+    ActiveRecord::Base.time_zone_aware_types = cfg[:aware_types]
+  end
   if cfg.has_key?(:zone)
     Time.zone = cfg[:zone]
   end
   yield
 ensure
   ActiveRecord.default_timezone = old_default_zone
   ActiveRecord::Base.time_zone_aware_attributes = old_awareness
+  ActiveRecord::Base.time_zone_aware_types = old_aware_types
   Time.zone = old_zone
 end
 
 # This method makes sure that tests don't leak global state related to time zones.
 EXPECTED_ZONE = nil
 EXPECTED_DEFAULT_TIMEZONE = :utc
+EXPECTED_AWARE_TYPES = [:datetime, :time]
 EXPECTED_TIME_ZONE_AWARE_ATTRIBUTES = false
 def verify_default_timezone_config
   if Time.zone != EXPECTED_ZONE
@@ -149,6 +155,14 @@ def verify_default_timezone_config
       Got: #{ActiveRecord::Base.time_zone_aware_attributes}
     MSG
   end
+  if ActiveRecord::Base.time_zone_aware_types != EXPECTED_AWARE_TYPES
+    $stderr.puts <<-MSG
+\n#{self}
+    Global state `ActiveRecord::Base.time_zone_aware_types` was leaked.
+      Expected: #{EXPECTED_AWARE_TYPES}
+      Got: #{ActiveRecord::Base.time_zone_aware_types}
+    MSG
+  end
 end
 
 def enable_extension!(extension, connection)

railties/test/application/configuration_test.rb

@@ -3974,6 +3974,51 @@ def new(app); self; end
       assert_equal ActiveSupport::Cache::Coders::Rails61Coder, Rails.cache.instance_variable_get(:@coder)
     end
 
+    test "adds a time zone aware type if using PostgreSQL" do
+      original_configurations = ActiveRecord::Base.configurations
+      ActiveRecord::Base.configurations = { production: { db1: { adapter: "postgresql" } } }
+      app_file "config/initializers/active_record.rb", <<~RUBY
+        ActiveRecord::Base.establish_connection(adapter: "postgresql")
+      RUBY
+
+      app "production"
+
+      assert_equal [:datetime, :time, :timestamptz], ActiveRecord::Base.time_zone_aware_types
+    ensure
+      ActiveRecord::Base.configurations = original_configurations
+    end
+
+    test "doesn't add a time zone aware type if using MySQL" do
+      original_configurations = ActiveRecord::Base.configurations
+      ActiveRecord::Base.configurations = { production: { db1: { adapter: "mysql2" } } }
+      app_file "config/initializers/active_record.rb", <<~RUBY
+        ActiveRecord::Base.establish_connection(adapter: "mysql2")
+      RUBY
+
+      app "production"
+
+      assert_equal [:datetime, :time], ActiveRecord::Base.time_zone_aware_types
+    ensure
+      ActiveRecord::Base.configurations = original_configurations
+    end
+
+    test "can opt out of extra time zone aware types if using PostgreSQL" do
+      original_configurations = ActiveRecord::Base.configurations
+      ActiveRecord::Base.configurations = { production: { db1: { adapter: "postgresql" } } }
+      app_file "config/initializers/active_record.rb", <<~RUBY
+        ActiveRecord::Base.establish_connection(adapter: "postgresql")
+      RUBY
+      app_file "config/initializers/tz_aware_types.rb", <<~RUBY
+        ActiveRecord::Base.time_zone_aware_types -= [:timestamptz]
+      RUBY
+
+      app "production"
+
+      assert_equal [:datetime, :time], ActiveRecord::Base.time_zone_aware_types
+    ensure
+      ActiveRecord::Base.configurations = original_configurations
+    end
+
     private
       def set_custom_config(contents, config_source = "custom".inspect)
         app_file "config/custom.yml", contents