Allow navigation on history records without an at_value

lib/temporal_tables/association_extensions.rb

@@ -10,8 +10,12 @@ def target_scope
       # Using responds_to? results in an infinite loop stack overflow.
       if @owner.public_methods.include?(:at_value)
         # If this is a history record but no at time was given,
-        # assume the record's effective to date
-        super.at(@owner.at_value || @owner.eff_to)
+        # assume the record's effective to date minus 1 microsecond
+        # The logic here is to provide the association's history record at the end of
+        # the parent record's effective period. Since effective ranges are exclusive of
+        # the eff_to value, and the eff_* columns are datetime types with a precision of microseconds,
+        # 1 microsecond before eff_to is the end of the inclusive boundary to accomplish this.
+        super.at(@owner.at_value || (@owner.eff_to - TemporalTables::ONE_MICROSECOND))
       else
         super
       end

lib/temporal_tables/constants.rb

@@ -2,4 +2,5 @@
 
 module TemporalTables
   END_OF_TIME = '9999-12-31'
+  ONE_MICROSECOND = 0.000001.seconds
 end

spec/basic_history_spec.rb

@@ -229,6 +229,26 @@
       end
     end
   end
+
+  describe 'when removing a creature' do
+    let!(:wart) { Wart.create person: emily, hairiness: 3 }
+
+    before do
+      emily.destroy!
+      sleep 0.1
+    end
+
+    it 'destroys associated warts and we remember the historical association' do
+      expect(emily).to be_destroyed
+      expect { wart.reload }.to raise_error(ActiveRecord::RecordNotFound) # as it belonged to emily
+
+      wart_h = wart.history.last # the last version of the wart
+      expect(wart_h).to be_present
+
+      emily_h = wart_h.person
+      expect(emily_h).to be_present # we should be able to tell what person our wart belonged to
+    end
+  end
 end
 
 describe Bird do

spec/internal/app/models/person.rb

@@ -2,6 +2,6 @@
 
 class Person < ActiveRecord::Base
   belongs_to :coven
-  has_many :warts
+  has_many :warts, dependent: :destroy
   has_many :flying_machines
 end

temporal_tables.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |gem|
   gem.required_ruby_version = '>= 3.0.0'
   gem.metadata = { 'rubygems_mfa_required' => 'true' }
 
-  gem.add_dependency 'rails', '>= 6.0', '< 7.2'
+  gem.add_dependency 'rails', '>= 6.1', '< 7.2'
   gem.add_development_dependency 'combustion', '~> 1'
   gem.add_development_dependency 'database_cleaner'
   gem.add_development_dependency 'gemika', '~> 0.8'