Add active_record.postgresql_adapter_decode_dates

to toggle automatic decoding of dates column with the
PostgresqlAdapter.

PR rails#51483 is a breaking change and should have been gated behind a
config.

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Add `Rails.application.config.active_record.postgresql_adapter_decode_dates` to opt out of decoding dates automatically with the postgresql adapter. Defaults to true.
+
+    *Joé Dupuis*
+
 *   Add ENV["SKIP_TEST_DATABASE_TRUNCATE"] flag to speed up multi-process test runs on large DBs when all tests run within default txn. (This cuts ~10s from the test run of HEY when run by 24 processes against the 178 tables, since ~4,000 table truncates can then be skipped.)
 
     *DHH*

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -122,6 +122,15 @@ def dbconsole(config, options = {})
       # setting, you should immediately run <tt>bin/rails db:migrate</tt> to update the types in your schema.rb.
       class_attribute :datetime_type, default: :timestamp
 
+      ##
+      # :singleton-method:
+      # Toggles automatic decoding of date columns.
+      #
+      #   ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.select_value("select '2024-01-01'::date").class #=> String
+      #   ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.decode_dates = true
+      #   ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.select_value("select '2024-01-01'::date").class #=> Date
+      class_attribute :decode_dates, default: false
+
       NATIVE_DATABASE_TYPES = {
         primary_key: "bigserial primary key",
         string:      { name: "character varying" },
@@ -1159,8 +1168,8 @@ def add_pg_decoders
             "bool" => PG::TextDecoder::Boolean,
             "timestamp" => PG::TextDecoder::TimestampUtc,
             "timestamptz" => PG::TextDecoder::TimestampWithTimeZone,
-            "date" => PG::TextDecoder::Date,
           }
+          coders_by_name["date"] = PG::TextDecoder::Date if decode_dates
 
           known_coder_types = coders_by_name.keys.map { |n| quote(n) }
           query = <<~SQL % known_coder_types.join(", ")

activerecord/lib/active_record/railtie.rb

@@ -217,6 +217,16 @@ class Railtie < Rails::Railtie # :nodoc:
       end
     end
 
+    initializer "active_record.postgresql_adapter_decode_dates" do
+      config.after_initialize do
+        if config.active_record.postgresql_adapter_decode_dates
+          ActiveSupport.on_load(:active_record_postgresqladapter) do
+            self.decode_dates = true
+          end
+        end
+      end
+    end
+
     initializer "active_record.set_configs" do |app|
       configs = app.config.active_record
 
@@ -245,7 +255,8 @@ class Railtie < Rails::Railtie # :nodoc:
           :cache_query_log_tags,
           :sqlite3_adapter_strict_strings_by_default,
           :check_schema_cache_dump_version,
-          :use_schema_cache_dump
+          :use_schema_cache_dump,
+          :postgresql_adapter_decode_dates,
         )
 
         configs.each do |k, v|

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

@@ -39,10 +39,4 @@ def test_bc_date_year_zero
     topic = Topic.create!(last_read: date)
     assert_equal date, Topic.find(topic.id).last_read
   end
-
-  def test_date_decoder
-    date = ActiveRecord::Base.connection.select_value("select '2024-01-01'::date")
-    assert_equal Date.new(2024, 01, 01), date
-    assert_equal Date, date.class
-  end
 end

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

@@ -649,7 +649,25 @@ def test_does_not_raise_notice_level_warnings
         end
       end
 
+      def test_date_decoder
+        db_config = ActiveRecord::Base.configurations.configs_for(env_name: "arunit", name: "primary")
+        connection = ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.new(db_config.configuration_hash)
+
+        with_postgresql_apdater_decode_dates do
+          date = connection.select_value("select '2024-01-01'::date")
+          assert_equal Date.new(2024, 01, 01), date
+          assert_equal Date, date.class
+        end
+      end
+
       private
+        def with_postgresql_apdater_decode_dates
+          PostgreSQLAdapter.decode_dates = true
+          yield
+        ensure
+          PostgreSQLAdapter.decode_dates = false
+        end
+
         def with_example_table(definition = "id serial primary key, number integer, data character varying(255)", &block)
           super(@connection, "ex", definition, &block)
         end

guides/source/configuring.md

@@ -62,6 +62,7 @@ Below are the default values associated with each target version. In cases of co
 
 - [`config.active_job.enqueue_after_transaction_commit`](#config-active-job-enqueue-after-transaction-commit): `:default`
 - [`config.active_record.automatically_invert_plural_associations`](#config-active-record-automatically-invert-plural-associations): `true`
+- [`config.active_record.postgresql_adapter_decode_dates`](#config-active-record-postgresql-adapter-decode-dates): `true`
 - [`config.active_record.validate_migration_timestamps`](#config-active-record-validate-migration-timestamps): `true`
 - [`config.active_storage.web_image_content_types`](#config-active-storage-web-image-content-types): `%w[image/png image/jpeg image/gif image/webp]`
 
@@ -1490,6 +1491,24 @@ The default value depends on the `config.load_defaults` target version:
 | (original)            | `false`              |
 | 7.1                   | `true`               |
 
+#### `config.active_record.postgresql_adapter_decode_dates`
+
+Specifies whether the PostgresqlAdapter should decode date columns.
+
+```ruby
+ActiveRecord::Base.connection
+     .select_value("select '2024-01-01'::date").class #=> Date
+```
+
+
+The default value depends on the `config.load_defaults` target version:
+
+| Starting with version | The default value is |
+| --------------------- | -------------------- |
+| (original)            | `false`              |
+| 7.2                   | `true`               |
+
+
 #### `config.active_record.async_query_executor`
 
 Specifies how asynchronous queries are pooled.

guides/source/upgrading_ruby_on_rails.md

@@ -81,6 +81,17 @@ Upgrading from Rails 7.1 to Rails 7.2
 
 For more information on changes made to Rails 7.2 please see the [release notes](7_2_release_notes.html).
 
+### `PostgresqlAdapter` now decodes dates automatically
+
+Manual queries with columns of type date will automatically be decoded to `Date` objects.
+To disable this new behavior and return dates as `String`:
+
+```ruby
+# config/application.rb
+config.active_record.postgresql_adapter_decode_dates = false
+```
+
+
 Upgrading from Rails 7.0 to Rails 7.1
 -------------------------------------
 

railties/lib/rails/application/configuration.rb

@@ -327,6 +327,7 @@ def load_defaults(target_version)
           end
 
           if respond_to?(:active_record)
+            active_record.postgresql_adapter_decode_dates = true
             active_record.validate_migration_timestamps = true
             active_record.automatically_invert_plural_associations = true
           end

railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_7_2.rb.tt

@@ -66,3 +66,13 @@
 # on `Post`. With this option enabled, it will also look for a `:comments` association.
 #++
 # Rails.application.config.active_record.automatically_invert_plural_associations = true
+
+###
+# Controls whether the PostgresqlAdapter should decode dates automatically with  manual queries.
+#
+# Example:
+#   ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.select_value("select '2024-01-01'::date") #=> Date
+#
+# This query used to return a `String`.
+#++
+# Rails.application.config.active_record.postgresql_adapter_decode_dates = true

railties/test/application/configuration_test.rb

@@ -2793,6 +2793,40 @@ def index
       assert_equal false, ActiveRecord::Base.run_commit_callbacks_on_first_saved_instances_in_transaction
     end
 
+    test "PostgresqlAdapter.decode_dates is true by default for new apps" do
+      app_file "config/initializers/active_record.rb", <<~RUBY
+        ActiveRecord::Base.establish_connection(adapter: "postgresql", database: ":memory:")
+      RUBY
+
+      app "development"
+
+      assert_equal true, ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.decode_dates
+    end
+
+    test "PostgresqlAdapter.decode_dates is false by default for upgraded apps" do
+      remove_from_config '.*config\.load_defaults.*\n'
+      app_file "config/initializers/active_record.rb", <<~RUBY
+        ActiveRecord::Base.establish_connection(adapter: "postgresql", database: ":memory:")
+      RUBY
+
+      app "development"
+
+      assert_equal false, ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.decode_dates
+    end
+
+    test "PostgresqlAdapter.decode_dates can be configured via config.active_record.postgresql_adapter_decode_dates" do
+      remove_from_config '.*config\.load_defaults.*\n'
+      add_to_config "config.active_record.postgresql_adapter_decode_dates = true"
+
+      app_file "config/initializers/active_record.rb", <<~RUBY
+        ActiveRecord::Base.establish_connection(adapter: "postgresql", database: ":memory:")
+      RUBY
+
+      app "development"
+
+      assert_equal true, ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.decode_dates
+    end
+
     test "SQLite3Adapter.strict_strings_by_default is true by default for new apps" do
       app_file "config/initializers/active_record.rb", <<~RUBY
         ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")