Return a `Point` object from the PG Point type

This introduces a deprecation cycle to change the behavior of the
default point type in the PostgreSQL adapter. The old behavior will
continue to be available for the immediate future as `:legacy_point`.

The current behavior of returning an `Array` causes several problems,
the most significant of which is that we cannot differentiate between an
array of points, and a point itself in the case of a column with the
`point[]` type.

The attributes API gives us a reasonable way to have a proper
deprecation cycle for this change, so let's take advantage of it. If we
like this change, we can also add proper support for the other geometric
types (line, lseg, box, path, polygon, and circle), all of which are
just aliases for string today.

Fixes #20441

1 files changed, 23 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index 3674f672cb..5a6f42ba09 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -310,6 +310,7 @@ module ActiveRecord
       def load_schema!
         @columns_hash = connection.schema_cache.columns_hash(table_name)
         @columns_hash.each do |name, column|
+          warn_if_deprecated_type(column)
           define_attribute(
             name,
             connection.lookup_cast_type_from_column(column),
@@ -356,6 +357,28 @@ module ActiveRecord
           base.table_name
         end
       end
+
+      def warn_if_deprecated_type(column)
+        return if attributes_to_define_after_schema_loads.key?(column.name)
+        if column.respond_to?(:oid) && column.sql_type.start_with?("point")
+          if column.array?
+            array_arguments = ", array: true"
+          else
+            array_arguments = ""
+          end
+          ActiveSupport::Deprecation.warn(<<-WARNING.strip_heredoc)
+            The behavior of the `:point` type will be changing in Rails 5.1 to
+            return a `Point` object, rather than an `Array`. If you'd like to
+            keep the old behavior, you can add this line to #{self.name}:
+
+              attribute :#{column.name}, :legacy_point#{array_arguments}
+
+            If you'd like the new behavior today, you can add this line:
+
+              attribute :#{column.name}, :rails_5_1_point#{array_arguments}
+          WARNING
+        end
+      end
     end
   end
 end