Fixed issue with transitions using STI

lib/statesman/adapters/active_record.rb

@@ -158,13 +158,24 @@ def update_most_recents(most_recent_id = nil)
 
       def most_recent_transitions(most_recent_id = nil)
         if most_recent_id
-          transitions_of_parent.and(
+          concrete_transitions_of_parent.and(
             transition_table[:id].eq(most_recent_id).or(
               transition_table[:most_recent].eq(true),
             ),
           )
         else
-          transitions_of_parent.and(transition_table[:most_recent].eq(true))
+          concrete_transitions_of_parent.and(transition_table[:most_recent].eq(true))
+        end
+      end
+
+      def concrete_transitions_of_parent
+        if transition_sti?
+          transitions_of_parent.and(
+            transition_table[transition_class.inheritance_column].
+              eq(transition_class.name),
+          )
+        else
+          transitions_of_parent
         end
       end
 
@@ -263,13 +274,18 @@ def unique_indexes
           end
       end
 
-      def parent_join_foreign_key
-        association =
-          parent_model.class.
-            reflect_on_all_associations(:has_many).
-            find { |r| r.name.to_s == @association_name.to_s }
+      def transition_sti?
+        transition_class.column_names.include?(transition_class.inheritance_column)
+      end
 
-        association_join_primary_key(association)
+      def parent_association
+        parent_model.class.
+          reflect_on_all_associations(:has_many).
+          find { |r| r.name.to_s == @association_name.to_s }
+      end
+
+      def parent_join_foreign_key
+        association_join_primary_key(parent_association)
       end
 
       def association_join_primary_key(association)

spec/spec_helper.rb

@@ -48,6 +48,8 @@ def connection_failure
       my_namespace_my_active_record_model_transitions
       other_active_record_models
       other_active_record_model_transitions
+      sti_active_record_models
+      sti_active_record_model_transitions
     ]
     tables.each do |table_name|
       sql = "DROP TABLE IF EXISTS #{table_name};"
@@ -72,6 +74,15 @@ def prepare_other_transitions_table
       OtherActiveRecordModelTransition.reset_column_information
     end
 
+    def prepare_sti_model_table
+      CreateStiActiveRecordModelMigration.migrate(:up)
+    end
+
+    def prepare_sti_transitions_table
+      CreateStiActiveRecordModelTransitionMigration.migrate(:up)
+      StiActiveRecordModelTransition.reset_column_information
+    end
+
     MyNamespace::MyActiveRecordModelTransition.serialize(:metadata, JSON)
   end
 end

spec/statesman/adapters/active_record_spec.rb

@@ -12,6 +12,9 @@
 
     MyActiveRecordModelTransition.serialize(:metadata, JSON)
 
+    prepare_sti_model_table
+    prepare_sti_transitions_table
+
     Statesman.configure do
       # Rubocop requires described_class to be used, but this block
       # is instance_eval'd and described_class won't be defined
@@ -300,6 +303,57 @@
             from(true).to be_falsey
         end
       end
+
+      context "when transition uses STI" do
+        let(:sti_model) { StiActiveRecordModel.create }
+
+        let(:adapter_a) do
+          described_class.new(
+            StiAActiveRecordModelTransition,
+            sti_model,
+            observer,
+            { association_name: :sti_a_active_record_model_transitions },
+          )
+        end
+        let(:adapter_b) do
+          described_class.new(
+            StiBActiveRecordModelTransition,
+            sti_model,
+            observer,
+            { association_name: :sti_b_active_record_model_transitions },
+          )
+        end
+        let(:create) { adapter_a.create(from, to) }
+
+        context "with a previous unrelated transition" do
+          let!(:transition_b) { adapter_b.create(from, to) }
+
+          its(:most_recent) { is_expected.to eq(true) }
+
+          it "doesn't update the previous transition's most_recent flag" do
+            expect { create }.
+              to_not(change { transition_b.reload.most_recent })
+          end
+        end
+
+        context "with previous related and unrelated transitions" do
+          let!(:transition_a) { adapter_a.create(from, to) }
+          let!(:transition_b) { adapter_b.create(from, to) }
+
+          its(:most_recent) { is_expected.to eq(true) }
+
+          it "updates the previous transition's most_recent flag" do
+            expect { create }.
+              to change { transition_a.reload.most_recent }.
+              from(true).to be_falsey
+          end
+
+          it "doesn't update the previous unrelated transition's most_recent flag" do
+            expect { create }.
+              to_not(change { transition_b.reload.most_recent })
+          end
+        end
+      end
     end
   end
 

spec/support/active_record.rb

@@ -278,3 +278,94 @@ def change
     end
   end
 end
+
+class StiActiveRecordModel < ActiveRecord::Base
+  has_many :sti_a_active_record_model_transitions, autosave: false
+  has_many :sti_b_active_record_model_transitions, autosave: false
+
+  def state_machine_a
+    @state_machine_a ||= MyStateMachine.new(
+      self, transition_class: StiAActiveRecordModelTransition
+    )
+  end
+
+  def state_machine_b
+    @state_machine_b ||= MyStateMachine.new(
+      self, transition_class: StiBActiveRecordModelTransition
+    )
+  end
+
+  def metadata
+    super || {}
+  end
+
+  def reload(*)
+    state_machine_a.reset
+    state_machine_b.reset
+    super
+  end
+end
+
+class StiActiveRecordModelTransition < ActiveRecord::Base
+  include Statesman::Adapters::ActiveRecordTransition
+
+  belongs_to :sti_active_record_model
+  serialize :metadata, JSON
+end
+
+class StiAActiveRecordModelTransition < StiActiveRecordModelTransition
+end
+
+class StiBActiveRecordModelTransition < StiActiveRecordModelTransition
+end
+
+class CreateStiActiveRecordModelMigration < MIGRATION_CLASS
+  def change
+    create_table :sti_active_record_models do |t|
+      t.timestamps null: false
+    end
+  end
+end
+
+class CreateStiActiveRecordModelTransitionMigration < MIGRATION_CLASS
+  def change
+    create_table :sti_active_record_model_transitions do |t|
+      t.string  :to_state
+      t.integer :sti_active_record_model_id
+      t.integer :sort_key
+      t.string  :type
+
+      # MySQL doesn't allow default values on text fields
+      if ActiveRecord::Base.connection.adapter_name == "Mysql2"
+        t.text :metadata
+      else
+        t.text :metadata, default: "{}"
+      end
+
+      if Statesman::Adapters::ActiveRecord.database_supports_partial_indexes?
+        t.boolean :most_recent, default: true, null: false
+      else
+        t.boolean :most_recent, default: true
+      end
+
+      t.timestamps null: false
+    end
+
+    add_index :sti_active_record_model_transitions,
+              %i[type sti_active_record_model_id sort_key],
+              unique: true, name: "sti_sort_key_index"
+
+    if Statesman::Adapters::ActiveRecord.database_supports_partial_indexes?
+      add_index :sti_active_record_model_transitions,
+                %i[type sti_active_record_model_id most_recent],
+                unique: true,
+                where: "most_recent",
+                name: "index_sti_active_record_model_transitions_parent_latest"
+    else
+      add_index :sti_active_record_model_transitions,
+                %i[type sti_active_record_model_id most_recent],
+                unique: true,
+                name: "index_sti_active_record_model_transitions_parent_latest"
+    end
+  end
+end