Add compatibility for Ruby 2.4 `to_time` changes

In Ruby 2.4 the `to_time` method for both `DateTime` and `Time` will
preserve the timezone of the receiver when converting to an instance
of `Time`. Since Rails 5.0 will support Ruby 2.2, 2.3 and later we
need to introduce a compatibility layer so that apps that upgrade do
not break. New apps will have a config initializer file that defaults
to match the new Ruby 2.4 behavior going forward.

For information about the changes to Ruby see:
https://bugs.ruby-lang.org/issues/12189
https://bugs.ruby-lang.org/issues/12271

Fixes #24617.

1 files changed, 110 insertions, 0 deletions

diff --git a/activesupport/test/core_ext/date_and_time_compatibility_test.rb b/activesupport/test/core_ext/date_and_time_compatibility_test.rb
new file mode 100644
index 0000000000..7cc2fae5be
--- /dev/null
+++ b/activesupport/test/core_ext/date_and_time_compatibility_test.rb
@@ -0,0 +1,110 @@
+require 'abstract_unit'
+require 'active_support/time'
+require 'time_zone_test_helpers'
+
+class DateAndTimeCompatibilityTest < ActiveSupport::TestCase
+  include TimeZoneTestHelpers
+
+  def setup
+    @utc_time = Time.utc(2016, 4, 23, 14, 11, 12)
+    @utc_offset = 3600
+    @system_offset = -14400
+    @zone = ActiveSupport::TimeZone['London']
+  end
+
+  def test_time_to_time_preserves_timezone
+    with_preserve_timezone(true) do
+      with_env_tz 'US/Eastern' do
+        time = Time.new(2016, 4, 23, 15, 11, 12, 3600).to_time
+
+        assert_instance_of Time, time
+        assert_equal @utc_time, time.getutc
+        assert_equal @utc_offset, time.utc_offset
+      end
+    end
+  end
+
+  def test_time_to_time_does_not_preserve_time_zone
+    with_preserve_timezone(false) do
+      with_env_tz 'US/Eastern' do
+        time = Time.new(2016, 4, 23, 15, 11, 12, 3600).to_time
+
+        assert_instance_of Time, time
+        assert_equal @utc_time, time.getutc
+        assert_equal @system_offset, time.utc_offset
+      end
+    end
+  end
+
+  def test_datetime_to_time_preserves_timezone
+    with_preserve_timezone(true) do
+      with_env_tz 'US/Eastern' do
+        time = DateTime.new(2016, 4, 23, 15, 11, 12, Rational(1,24)).to_time
+
+        assert_instance_of Time, time
+        assert_equal @utc_time, time.getutc
+        assert_equal @utc_offset, time.utc_offset
+      end
+    end
+  end
+
+  def test_datetime_to_time_does_not_preserve_time_zone
+    with_preserve_timezone(false) do
+      with_env_tz 'US/Eastern' do
+        time = DateTime.new(2016, 4, 23, 15, 11, 12, Rational(1,24)).to_time
+
+        assert_instance_of Time, time
+        assert_equal @utc_time, time.getutc
+        assert_equal @system_offset, time.utc_offset
+      end
+    end
+  end
+
+  def test_twz_to_time_preserves_timezone
+    with_preserve_timezone(true) do
+      with_env_tz 'US/Eastern' do
+        time = ActiveSupport::TimeWithZone.new(@utc_time, @zone).to_time
+
+        assert_instance_of Time, time
+        assert_equal @utc_time, time.getutc
+        assert_equal @utc_offset, time.utc_offset
+      end
+    end
+  end
+
+  def test_twz_to_time_does_not_preserve_time_zone
+    with_preserve_timezone(false) do
+      with_env_tz 'US/Eastern' do
+        time = ActiveSupport::TimeWithZone.new(@utc_time, @zone).to_time
+
+        assert_instance_of Time, time
+        assert_equal @utc_time, time.getutc
+        assert_equal @system_offset, time.utc_offset
+      end
+    end
+  end
+
+  def test_string_to_time_preserves_timezone
+    with_preserve_timezone(true) do
+      with_env_tz 'US/Eastern' do
+        time = "2016-04-23T15:11:12+01:00".to_time
+
+        assert_instance_of Time, time
+        assert_equal @utc_time, time.getutc
+        assert_equal @utc_offset, time.utc_offset
+      end
+    end
+  end
+
+  def test_string_to_time_does_not_preserve_time_zone
+    with_preserve_timezone(false) do
+      with_env_tz 'US/Eastern' do
+        time = "2016-04-23T15:11:12+01:00".to_time
+
+        assert_instance_of Time, time
+        assert_equal @utc_time, time.getutc
+        assert_equal @system_offset, time.utc_offset
+      end
+    end
+  end
+end