allow configuring behavior of nested transactions #107

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 ## 3.1.0 (not yet released)
 
+ * allow configuring behavior of nested transactions (see [issue #107](https://github.com/aasm/aasm/issues/107))
  * validating the current state (see [issue #95](https://github.com/aasm/aasm/issues/95), thanks to [@ivantsepp](https://github.com/ivantsepp))
 
 ## 3.0.26

README.md

@@ -339,6 +339,28 @@ class Job < ActiveRecord::Base
 end
 ```
 
+If you want to encapsulate state changes within an own transaction, the behavior
+of this nested transaction might be confusing. Take a look at
+[ActiveRecord Nested Transactions](http://api.rubyonrails.org/classes/ActiveRecord/Transactions/ClassMethods.html)
+if you want to know more about this. Nevertheless, AASM by default requires a new transaction
+`transaction(:requires_new => true)`. You can override this behavior by changing
+the configuration
+
+```ruby
+class Job < ActiveRecord::Base
+  include AASM
+
+  aasm :requires_new_transaction => false do
+    ...
+  end
+
+  ...
+end
+```
+
+which then leads to `transaction(:requires_new => false)`, the Rails default.
+
+
 ### Column name & migration
 
 As a default AASM uses the column `aasm_state` to store the states. You can override

lib/aasm/base.rb

@@ -23,6 +23,12 @@ module AASM
       elsif @state_machine.config.skip_validation_on_save.nil?
         @state_machine.config.skip_validation_on_save = false # this is the default, so don't store any new state if the model is invalid
       end
+
+      if options.key?(:requires_new_transaction)
+        @state_machine.config.requires_new_transaction = options[:requires_new_transaction]
+      elsif @state_machine.config.requires_new_transaction.nil?
+        @state_machine.config.requires_new_transaction = true # use requires_new for nested transactions
+      end
     end
 
     def initial_state(new_initial_state=nil)

lib/aasm/persistence/active_record_persistence.rb

@@ -138,7 +138,7 @@ module AASM
         end
 
         def aasm_fire_event(name, options, *args, &block)
-          success = self.class.transaction(:requires_new => true) do
+          success = self.class.transaction(:requires_new => requires_new?) do
             super
           end
 
@@ -150,6 +150,10 @@ module AASM
           success
         end
 
+        def requires_new?
+          AASM::StateMachine[self.class].config.requires_new_transaction
+        end
+
         def aasm_validate_states
           unless AASM::StateMachine[self.class].config.skip_validation_on_save
             if aasm.current_state && !aasm.states.include?(aasm.current_state)

spec/unit/persistence/active_record_persistence_spec.rb

@@ -173,6 +173,7 @@ describe 'transitions with persistence' do
       expect(worker.reload.status).to eq('sleeping')
     end
 
+    context "nested transactions" do
       it "should rollback all changes in nested transaction" do
         expect(transactor).to be_sleeping
         expect(worker.status).to eq('sleeping')
@@ -185,6 +186,22 @@ describe 'transitions with persistence' do
         expect(worker.reload.status).to eq('sleeping')
       end
 
+      it "should only rollback changes in the main transaction not the nested one" do
+        # change configuration to not require new transaction
+        AASM::StateMachine[Transactor].config.requires_new_transaction = false
+
+        expect(transactor).to be_sleeping
+        expect(worker.status).to eq('sleeping')
+
+        Worker.transaction do
+          expect { transactor.run! }.to raise_error(StandardError, 'failed on purpose')
+        end
+
+        expect(transactor).to be_running
+        expect(worker.reload.status).to eq('running')
+      end
+    end
+
     describe "after_commit callback" do
       it "should fire :after_commit if transaction was successful" do
         validator = Validator.create(:name => 'name')