Allow custom handling of non-standard types in `time_zone_conversion`

PostgreSQL for example, allows infinity as a valid value for date time
columns. The PG type has explicit handling for that case. However, time
zone conversion will end up trampling that handling. Unfortunately, we
can't call super and then convert time zones.

However, if we get back nil from `.in_time_zone`, it's something we
didn't expect so we can let the superclass handle it.

Fixes #17971

2 files changed, 7 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
index 33d9d2002c..87274dd4e1 100644
--- a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
+++ b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
@@ -12,7 +12,7 @@ module ActiveRecord
           if value.is_a?(Array)
             value.map { |v| type_cast_from_user(v) }
           elsif value.respond_to?(:in_time_zone)
-            value.in_time_zone
+            value.in_time_zone || super
           end
         end
 
diff --git a/activerecord/test/cases/adapters/postgresql/infinity_test.rb b/activerecord/test/cases/adapters/postgresql/infinity_test.rb
index 22e8873333..30404cd181 100644
--- a/activerecord/test/cases/adapters/postgresql/infinity_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/infinity_test.rb
@@ -41,4 +41,10 @@ class PostgresqlInfinityTest < ActiveRecord::TestCase
     record.reload
     assert_equal Float::INFINITY, record.datetime
   end
+
+  test "assigning 'infinity' on a datetime column" do
+    record = PostgresqlInfinity.create!(datetime: "infinity")
+    assert_equal Float::INFINITY, record.datetime
+    assert_equal record.datetime, record.reload.datetime
+  end
 end