Fix rollback of primarykey-less tables

If you have a table without a primary key, and an `after_commit` callback on that table (ie `has_transactional_callbacks?` returns true), then trying to rollback a transaction involving that record would result in “ActiveModel::MissingAttributeError: can't write unknown attribute ``”

2 files changed, 23 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/transactions.rb b/activerecord/lib/active_record/transactions.rb
index 31ca90fb58..97648ec898 100644
--- a/activerecord/lib/active_record/transactions.rb
+++ b/activerecord/lib/active_record/transactions.rb
@@ -387,7 +387,7 @@ module ActiveRecord
           thaw unless restore_state[:frozen?]
           @new_record = restore_state[:new_record]
           @destroyed  = restore_state[:destroyed]
-          write_attribute(self.class.primary_key, restore_state[:id])
+          write_attribute(self.class.primary_key, restore_state[:id]) if self.class.primary_key
         end
       end
     end
diff --git a/activerecord/test/cases/transactions_test.rb b/activerecord/test/cases/transactions_test.rb
index e0aecb5996..a89c24f57e 100644
--- a/activerecord/test/cases/transactions_test.rb
+++ b/activerecord/test/cases/transactions_test.rb
@@ -653,6 +653,28 @@ class TransactionTest < ActiveRecord::TestCase
     assert transaction.state.committed?
   end
 
+  def test_transaction_rollback_with_primarykeyless_tables
+    connection = ActiveRecord::Base.connection
+    connection.create_table(:transaction_without_primary_keys, force: true, id: false) do |t|
+       t.integer :thing_id
+    end
+    
+    klass = Class.new(ActiveRecord::Base) do
+      self.table_name = 'transaction_without_primary_keys'
+      after_commit { } # necessary to trigger the has_transactional_callbacks branch
+    end
+
+    assert_no_difference(-> { klass.count }) do
+      ActiveRecord::Base.transaction do
+        klass.create!
+        raise ActiveRecord::Rollback
+      end
+    end
+    
+  ensure
+    connection.execute("DROP TABLE IF EXISTS transaction_without_primary_keys")
+  end
+
   private
 
   %w(validation save destroy).each do |filter|