Fix import of saved json[b] fields for postgres

lib/activerecord-import/import.rb

@@ -577,7 +577,10 @@ def import_helper( *args )
         default_values = column_defaults
         stored_attrs = respond_to?(:stored_attributes) ? stored_attributes : {}
         serialized_attrs = if defined?(ActiveRecord::Type::Serialized)
-          attrs = column_names.select { |c| type_for_attribute(c.to_s).class == ActiveRecord::Type::Serialized }
+          attrs = column_names.select { |c|
+            attribute_type = type_for_attribute(c.to_s)
+            attribute_type.class == ActiveRecord::Type::Serialized || %i[json jsonb].include?(attribute_type.type)
+          }
           Hash[attrs.map { |a| [a, nil] }]
         else
           serialized_attributes

test/schema/postgresql_schema.rb

@@ -8,6 +8,7 @@
     t.text :preferences
 
     if t.respond_to?(:json)
+      t.json :pure_json_data
       t.json :data
     else
       t.text :data
@@ -20,6 +21,7 @@
     end
 
     if t.respond_to?(:jsonb)
+      t.jsonb :pure_jsonb_data
       t.jsonb :settings
       t.jsonb :json_data, null: false, default: {}
     else

test/support/postgresql/import_examples.rb

@@ -234,6 +234,19 @@ def should_support_postgresql_import_functionality
         assert_equal({}, Vendor.first.json_data)
       end
     end
+
+    %w[json jsonb].each do |json_type|
+      describe "with pure #{json_type} fields" do
+        let(:data) { {a: :b} }
+        let(:json_field_name) { "pure_#{json_type}_data" }
+        it "imports the values from saved records" do
+          vendor = Vendor.create!(name: 'Vendor 1', json_field_name => data)
+
+          Vendor.import [vendor], on_duplicate_key_update: [json_field_name]
+          assert_equal(data.as_json, vendor.reload[json_field_name])
+        end
+      end
+    end
   end
 
   describe "with binary field" do