Add from state method to transition history

lib/generators/statesman/templates/active_record_transition_model.rb.erb

@@ -9,7 +9,7 @@ class <%= klass %> < <%= Statesman::Utils.rails_5_or_higher? ? 'ApplicationRecor
   # self.updated_timestamp_column = nil
 
 <%- unless Statesman::Utils.rails_4_or_higher? -%>
-  attr_accessible :to_state, :metadata, :sort_key
+  attr_accessible :from_state, :to_state, :metadata, :sort_key
 
 <%- end -%>
   belongs_to :<%= parent_name %><%= class_name_option %>, inverse_of: :<%= table_name %>

lib/generators/statesman/templates/create_migration.rb.erb

@@ -1,6 +1,7 @@
 class Create<%= migration_class_name %> < ActiveRecord::Migration<%= "[#{ActiveRecord::Migration.current_version}]" if Statesman::Utils.rails_5_or_higher? %>
   def change
     create_table :<%= table_name %> do |t|
+      t.string :from_state, null: false
       t.string :to_state, null: false
       t.text :metadata<%= ", default: #{metadata_default_value}" unless mysql? %>
       t.integer :sort_key, null: false

lib/generators/statesman/templates/update_migration.rb.erb

@@ -1,5 +1,6 @@
 class AddStatesmanTo<%= migration_class_name %> < ActiveRecord::Migration<%= "[#{ActiveRecord::Migration.current_version}]" if Statesman::Utils.rails_5_or_higher? %>
   def change
+    add_column :<%= table_name %>, :from_state, :string, null: false
     add_column :<%= table_name %>, :to_state, :string, null: false
     add_column :<%= table_name %>, :metadata, :text<%= ", default: #{metadata_default_value}" unless mysql? %>
     add_column :<%= table_name %>, :sort_key, :integer, null: false

lib/statesman/adapters/active_record.rb

@@ -81,7 +81,7 @@ def reset
 
       def create_transition(from, to, metadata)
         transition = transitions_for_parent.build(
-          default_transition_attributes(to, metadata),
+          default_transition_attributes(from, to, metadata),
         )
 
         transition_class.transaction(requires_new: true) do
@@ -116,13 +116,19 @@ def create_transition(from, to, metadata)
         transition
       end
 
-      def default_transition_attributes(to, metadata)
-        {
+      def default_transition_attributes(from, to, metadata)
+        attributes = {
           to_state: to,
           sort_key: next_sort_key,
           metadata: metadata,
           most_recent: not_most_recent_value(db_cast: false),
         }
+
+        if @transition_class.has_attribute?(:from_state)
+          attributes[:from_state] = from
+        end
+
+        attributes
       end
 
       def add_after_commit_callback(from, to, transition)

lib/statesman/adapters/active_record_transition.rb

@@ -19,6 +19,12 @@ module ActiveRecordTransition
         class_attribute :updated_timestamp_column
         self.updated_timestamp_column = DEFAULT_UPDATED_TIMESTAMP_COLUMN
       end
+
+      def from_state
+        if has_attribute?(:from_state)
+          self[:from_state]
+        end
+      end
     end
   end
 end

lib/statesman/adapters/memory.rb

@@ -20,7 +20,7 @@ def initialize(transition_class, parent_model, observer, _opts = {})
       def create(from, to, metadata = {})
         from = from.to_s
         to = to.to_s
-        transition = transition_class.new(to, next_sort_key, metadata)
+        transition = transition_class.new(from, to, next_sort_key, metadata)
 
         @observer.execute(:before, from, to, transition)
         @history << transition

lib/statesman/adapters/memory_transition.rb

@@ -5,13 +5,15 @@ module Adapters
     class MemoryTransition
       attr_accessor :created_at
       attr_accessor :updated_at
+      attr_accessor :from_state
       attr_accessor :to_state
       attr_accessor :sort_key
       attr_accessor :metadata
 
-      def initialize(to, sort_key, metadata = {})
+      def initialize(from, to, sort_key, metadata = {})
         @created_at = Time.now
         @updated_at = Time.now
+        @from_state = from
         @to_state = to
         @sort_key = sort_key
         @metadata = metadata

spec/statesman/adapters/memory_transition_spec.rb

@@ -4,18 +4,20 @@
 
 describe Statesman::Adapters::MemoryTransition do
   describe "#initialize" do
+    let(:from) { :n }
     let(:to) { :y }
     let(:sort_key) { 0 }
-    let(:create) { described_class.new(to, sort_key) }
+    let(:create) { described_class.new(from, to, sort_key) }
 
+    specify { expect(create.from_state).to equal(from) }
     specify { expect(create.to_state).to equal(to) }
     specify { expect(create.created_at).to be_a(Time) }
     specify { expect(create.updated_at).to be_a(Time) }
     specify { expect(create.sort_key).to be(sort_key) }
 
     context "with metadata passed" do
       let(:metadata) { { some: :hash } }
-      let(:create) { described_class.new(to, sort_key, metadata) }
+      let(:create) { described_class.new(from, to, sort_key, metadata) }
 
       specify { expect(create.metadata).to eq(metadata) }
     end

spec/support/active_record.rb

@@ -70,6 +70,7 @@ def change
 class CreateMyActiveRecordModelTransitionMigration < MIGRATION_CLASS
   def change
     create_table :my_active_record_model_transitions do |t|
+      t.string  :from_state
       t.string  :to_state
       t.integer :my_active_record_model_id
       t.integer :sort_key
@@ -189,6 +190,7 @@ def change
 class CreateOtherActiveRecordModelTransitionMigration < MIGRATION_CLASS
   def change
     create_table :other_active_record_model_transitions do |t|
+      t.string  :from_state
       t.string  :to_state
       t.integer :other_active_record_model_id
       t.integer :sort_key
@@ -284,6 +286,7 @@ def change
 class CreateNamespacedARModelTransitionMigration < MIGRATION_CLASS
   def change
     create_table :my_namespace_my_active_record_model_transitions do |t|
+      t.string  :from_state
       t.string  :to_state
       t.integer :my_active_record_model_id
       t.integer :sort_key