Re-roll deprecation of to_time_preserves_timezone

We realised the previous deprecation hadn't been warning for all users.

activesupport/lib/active_support.rb

@@ -117,7 +117,7 @@ module ActiveSupport
   def self.to_time_preserves_timezone=(value)
     unless value
       ActiveSupport.deprecator.warn(
-        "Support for the pre-Ruby 2.4 behavior of to_time has been deprecated and will be removed in Rails 7.2."
+        "Support for the pre-Ruby 2.4 behavior of to_time has been deprecated and will be removed in Rails 8.0."
       )
     end
 

activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/module/redefine_method"
 
 module DateAndTime
   module Compatibility
@@ -11,7 +12,33 @@ module DateAndTime
     # of the receiver. For backwards compatibility we're overriding
     # this behavior, but new apps will have an initializer that sets
     # this to true, because the new behavior is preferred.
-    mattr_accessor :preserve_timezone, instance_writer: false, default: false
+    mattr_accessor :preserve_timezone, instance_accessor: false, default: nil
+
+    singleton_class.silence_redefinition_of_method :preserve_timezone
+
+    #--
+    # This re-implements the behaviour of the mattr_reader, instead
+    # of prepending on to it, to avoid overcomplicating a module that
+    # is in turn included in several places. This will all go away in
+    # Rails 8.0 anyway.
+    def self.preserve_timezone # :nodoc:
+      if @@preserve_timezone.nil?
+        # Only warn once, the first time the value is used (which should
+        # be the first time #to_time is called).
+        ActiveSupport.deprecator.warn(
+          "to_time will always preserve the timezone offset of the receiver in Rails 8.0. " \
+          "To opt in to the new behavior, set `ActiveSupport.to_time_preserves_timezone = true`."
+        )
+
+        @@preserve_timezone = false
+      end
+
+      @@preserve_timezone
+    end
+
+    def preserve_timezone # :nodoc:
+      Compatibility.preserve_timezone
+    end
 
     # Change the output of <tt>ActiveSupport::TimeZone.utc_to_local</tt>.
     #

activesupport/test/core_ext/date_and_time_compatibility_test.rb

@@ -287,6 +287,20 @@ class DateAndTimeCompatibilityTest < ActiveSupport::TestCase
     assert_deprecated(ActiveSupport.deprecator) do
       ActiveSupport.to_time_preserves_timezone = false
     end
+
+    assert_deprecated(ActiveSupport.deprecator) do
+      ActiveSupport.to_time_preserves_timezone = nil
+    end
+
+    # When set to nil, the first call will report a deprecation,
+    # then switch the configured value to (and return) false.
+    assert_deprecated(ActiveSupport.deprecator) do
+      assert_equal false, ActiveSupport.to_time_preserves_timezone
+    end
+
+    assert_not_deprecated(ActiveSupport.deprecator) do
+      ActiveSupport.to_time_preserves_timezone
+    end
   ensure
     ActiveSupport.deprecator.silence do
       ActiveSupport.to_time_preserves_timezone = current_preserve_tz

activesupport/test/core_ext/time_with_zone_test.rb

@@ -543,6 +543,21 @@ class TimeWithZoneTest < ActiveSupport::TestCase
     end
   end
 
+  def test_to_time_without_preserve_timezone_configured
+    with_preserve_timezone(nil) do
+      with_env_tz "US/Eastern" do
+        time = assert_deprecated(ActiveSupport.deprecator) { @twz.to_time }
+
+        assert_equal Time, time.class
+        assert_equal time.object_id, @twz.to_time.object_id
+        assert_equal Time.local(1999, 12, 31, 19), time
+        assert_equal Time.local(1999, 12, 31, 19).utc_offset, time.utc_offset
+
+        assert_equal false, ActiveSupport.to_time_preserves_timezone
+      end
+    end
+  end
+
   def test_to_date
     # 1 sec before midnight Jan 1 EST
     assert_equal Date.new(1999, 12, 31), ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 4, 59, 59), ActiveSupport::TimeZone["Eastern Time (US & Canada)"]).to_date