Merge pull request #310 from gocardless/issue-309

Support ActiveRecord transitions which don't include Statesman::Adapters::ActiveRecordTransition

README.md

@@ -121,7 +121,7 @@ Order.not_in_state(:checking_out) # => [#<Order id: "123">]
 
 By default Statesman stores transition history in memory only. It can be
 persisted by configuring Statesman to use a different adapter. For example,
-ActiveRecord within Rails:
+for ActiveRecord within Rails:
 
 `config/initializers/statesman.rb`:
 
@@ -137,6 +137,10 @@ Generate the transition model:
 $ rails g statesman:active_record_transition Order OrderTransition
 ```
 
+Your transition class should
+`include Statesman::Adapters::ActiveRecordTransition` if you're using the
+ActiveRecord adapter.
+
 If you're using the ActiveRecord adapter and decide not to include the default
 `updated_at` column in your transition table, you'll need to configure the
 `updated_timestamp_column` option on the transition class, setting it to another column
@@ -178,8 +182,12 @@ or 5. To do that
   t.json :metadata, default: {}
   ```
 
-* Remove `include Statesman::Adapters::ActiveRecordTransition` statement from your
-  transition model
+* Remove the `include Statesman::Adapters::ActiveRecordTransition` statement from
+  your transition model. (If you want to customise your transition class's "updated
+  timestamp column", as described above, you should define a
+  `.updated_timestamp_column` method on your class and return the name of the column
+  as a symbol, or `nil` if you don't want to record an updated timestamp on
+  transitions.)
 
 ## Configuration
 

lib/statesman/adapters/active_record.rb

@@ -123,15 +123,28 @@ def transition_conflict_error?(e)
       end
 
       def with_updated_timestamp(params)
-        return params if @transition_class.updated_timestamp_column.nil?
+        # TODO: Once we've set expectations that transition classes should conform to
+        # the interface of Adapters::ActiveRecordTransition as a breaking change in the
+        # next major version, we can stop calling `#respond_to?` first and instead
+        # assume that there is a `.updated_timestamp_column` method we can call.
+        #
+        # At the moment, most transition classes will include the module, but not all,
+        # not least because it doesn't work with PostgreSQL JSON columns for metadata.
+        column = if @transition_class.respond_to?(:updated_timestamp_column)
+                   @transition_class.updated_timestamp_column
+                 else
+                   ActiveRecordTransition::DEFAULT_UPDATED_TIMESTAMP_COLUMN
+                 end
+
+        return params if column.nil?
 
         timestamp = if ::ActiveRecord::Base.default_timezone == :utc
                       Time.now.utc
                     else
                       Time.now
                     end
 
-        params.merge(@transition_class.updated_timestamp_column => timestamp)
+        params.merge(column => timestamp)
       end
     end
   end

spec/statesman/adapters/active_record_spec.rb

@@ -163,6 +163,19 @@
             to(change { previous_transition.reload.updated_at })
         end
 
+        context "for a transition class without an updated timestamp column attribute" do
+          let!(:adapter) do
+            described_class.new(MyActiveRecordModelTransitionWithoutInclude,
+                                model,
+                                observer)
+          end
+
+          it "defaults to touching the previous transition's updated_at timestamp" do
+            expect { Timecop.freeze(Time.now + 5.seconds) { create } }.
+              to(change { previous_transition.reload.updated_at })
+          end
+        end
+
         context "with a custom updated timestamp column set" do
           around do |example|
             MyActiveRecordModelTransition.updated_timestamp_column.tap do |original_value|

spec/support/active_record.rb

@@ -40,6 +40,13 @@ class MyActiveRecordModelTransition < ActiveRecord::Base
   serialize :metadata, JSON
 end
 
+class MyActiveRecordModelTransitionWithoutInclude < ActiveRecord::Base
+  self.table_name = "my_active_record_model_transitions"
+
+  belongs_to :my_active_record_model
+  serialize :metadata, JSON
+end
+
 class CreateMyActiveRecordModelMigration < MIGRATION_CLASS
   def change
     create_table :my_active_record_models do |t|