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, 50 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/rails_5_1_point.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/rails_5_1_point.rb
new file mode 100644
index 0000000000..7427a25ad5
--- /dev/null
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/rails_5_1_point.rb
@@ -0,0 +1,50 @@
+module ActiveRecord
+  Point = Struct.new(:x, :y)
+
+  module ConnectionAdapters
+    module PostgreSQL
+      module OID # :nodoc:
+        class Rails51Point < Type::Value # :nodoc:
+          include Type::Helpers::Mutable
+
+          def type
+            :point
+          end
+
+          def cast(value)
+            case value
+            when ::String
+              if value[0] == '(' && value[-1] == ')'
+                value = value[1...-1]
+              end
+              x, y = value.split(",")
+              build_point(x, y)
+            when ::Array
+              build_point(*value)
+            else
+              value
+            end
+          end
+
+          def serialize(value)
+            if value.is_a?(ActiveRecord::Point)
+              "(#{number_for_point(value.x)},#{number_for_point(value.y)})"
+            else
+              super
+            end
+          end
+
+          private
+
+          def number_for_point(number)
+            number.to_s.gsub(/\.0$/, '')
+          end
+
+          def build_point(x, y)
+            ActiveRecord::Point.new(Float(x), Float(y))
+          end
+        end
+      end
+    end
+  end
+end