4-1-stable backportable patch of https://github.com/rails/rails/issues/15369

patch.diff

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index c39240d..a8d3723 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Keep PostgreSQL `hstore` and `json` attributes as `Hash` in `@attributes`.
+    Fixes duplication in combination with `store_accessor`.
+
+    Fixes #15369.
+
+    *Yves Senn*
+
 *   `rake railties:install:migrations` respects the order of railties.
 
     *Arun Agrawal*
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
index 7878c8f..947ac05 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
@@ -231,7 +231,10 @@ module ActiveRecord
 
         class Hstore < Type
           def type_cast_for_write(value)
-            ConnectionAdapters::PostgreSQLColumn.hstore_to_string value
+            # roundtrip to ensure uniform uniform types
+            # TODO: This is not an efficient solution.
+            stringified = ConnectionAdapters::PostgreSQLColumn.hstore_to_string(value)
+            type_cast(stringified)
           end
 
           def type_cast(value)
@@ -255,7 +258,10 @@ module ActiveRecord
 
         class Json < Type
           def type_cast_for_write(value)
-            ConnectionAdapters::PostgreSQLColumn.json_to_string value
+            # roundtrip to ensure uniform uniform types
+            # TODO: This is not an efficient solution.
+            stringified = ConnectionAdapters::PostgreSQLColumn.json_to_string(value)
+            type_cast(stringified)
           end
 
           def type_cast(value)
diff --git a/activerecord/test/cases/adapters/postgresql/hstore_test.rb b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
index f250243..b76fc45 100644
--- a/activerecord/test/cases/adapters/postgresql/hstore_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
@@ -126,6 +126,16 @@ class PostgresqlHstoreTest < ActiveRecord::TestCase
       assert_equal "GMT", x.timezone
     end
 
+    def test_duplication_with_store_accessors
+      x = Hstore.new(language: "fr", timezone: "GMT")
+      assert_equal "fr", x.language
+      assert_equal "GMT", x.timezone
+
+      y = x.dup
+      assert_equal "fr", y.language
+      assert_equal "GMT", y.timezone
+    end
+
     def test_gen1
       assert_equal(%q(" "=>""), @column.class.hstore_to_string({' '=>''}))
     end
diff --git a/activerecord/test/cases/adapters/postgresql/json_test.rb b/activerecord/test/cases/adapters/postgresql/json_test.rb
index 3daef39..fa98f81 100644
--- a/activerecord/test/cases/adapters/postgresql/json_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/json_test.rb
@@ -122,6 +122,14 @@ class PostgresqlJSONTest < ActiveRecord::TestCase
     assert_equal "640×1136", x.resolution
   end
 
+  def test_duplication_with_store_accessors
+    x = JsonDataType.new(resolution: "320×480")
+    assert_equal "320×480", x.resolution
+
+    y = x.dup
+    assert_equal "320×480", y.resolution
+  end
+
   def test_update_all
     json = JsonDataType.create! payload: { "one" => "two" }