Fix default_order_by_id for association loading

Add placeholder_literalizer_loader hook so the extension applies
ORDER BY id to Sequel association queries that use the optimized
loader path.

Add tests to buildpack and CNB lifecycle data model specs verifying
the association is ordered by id via the extension.

Author: johha

lib/sequel/extensions/default_order_by_id.rb

@@ -2,7 +2,8 @@
 
 # Sequel extension that adds default ORDER BY id to model queries.
 #
-# Hooks into fetch methods (all, each, first) to add ORDER BY id just before
+# Hooks into fetch methods (all, each, first) and placeholder_literalizer_loader
+# (used for optimized association loading) to add ORDER BY id just before
 # execution. This ensures ordering is only added to the final query, not to
 # subqueries or compound query parts.
 #
@@ -47,6 +48,13 @@ def first(*, &)
         ds.first(*, &)
       end
 
+      def placeholder_literalizer_loader(&block)
+        super do |pl, ds|
+          result_ds = block.call(pl, ds)
+          result_ds.send(:default_order_by_id) || result_ds
+        end
+      end
+
       private
 
       def default_order_by_id

spec/unit/lib/sequel/extensions/default_order_by_id_spec.rb

@@ -153,4 +153,32 @@ def capture_sql(&)
       end
     end
   end
+
+  describe 'association loading (placeholder_literalizer_loader)' do
+    let(:child_class) { Class.new(Sequel::Model(db[:test_default_order_join])) }
+
+    it 'adds ORDER BY id to association queries' do
+      child = child_class
+      parent_class = Class.new(Sequel::Model(db[:test_default_order_main])) do
+        define_singleton_method(:name) { 'TestParent' } # vcap_relations plugin derives reciprocal from self.name
+        one_to_many :children, class: child, key: :main_id
+      end
+      parent = parent_class.new
+      parent.values[:id] = 1
+      sql = capture_sql { parent.children }
+      expect(sql).to match(/ORDER BY .id./)
+    end
+
+    it 'does not override explicit association order' do
+      child = child_class
+      parent_class = Class.new(Sequel::Model(db[:test_default_order_main])) do
+        define_singleton_method(:name) { 'TestParent' }
+        one_to_many :children, class: child, key: :main_id, order: Sequel.desc(:id)
+      end
+      parent = parent_class.new
+      parent.values[:id] = 1
+      sql = capture_sql { parent.children }
+      expect(sql).to match(/ORDER BY .id. DESC/)
+    end
+  end
 end

spec/unit/models/runtime/buildpack_lifecycle_data_model_spec.rb

@@ -11,6 +11,24 @@ module VCAP::CloudController
       let(:attr_salt) { :encrypted_buildpack_url_salt }
     end
 
+    describe 'buildpack_lifecycle_buildpacks association' do
+      it 'orders by id via the default_order_by_id extension' do
+        lifecycle_data.save
+        lifecycle_data.reload
+
+        sqls = []
+        logger = Logger.new(StringIO.new)
+        logger.define_singleton_method(:info) { |msg| sqls << msg }
+        BuildpackLifecycleDataModel.db.loggers << logger
+
+        lifecycle_data.buildpack_lifecycle_buildpacks
+
+        BuildpackLifecycleDataModel.db.loggers.delete(logger)
+        sql = sqls.find { |s| s.include?('buildpack_lifecycle_buildpacks') }
+        expect(sql).to match(/ORDER BY .id./)
+      end
+    end
+
     describe '#stack' do
       it 'persists the stack' do
         lifecycle_data.stack = 'cflinuxfs4'

spec/unit/models/runtime/cnb_lifecycle_data_model_spec.rb

@@ -4,6 +4,23 @@ module VCAP::CloudController
   RSpec.describe CNBLifecycleDataModel do
     subject(:lifecycle_data) { CNBLifecycleDataModel.make([]) }
 
+    describe 'buildpack_lifecycle_buildpacks association' do
+      it 'orders by id via the default_order_by_id extension' do
+        lifecycle_data.reload
+
+        sqls = []
+        logger = Logger.new(StringIO.new)
+        logger.define_singleton_method(:info) { |msg| sqls << msg }
+        CNBLifecycleDataModel.db.loggers << logger
+
+        lifecycle_data.buildpack_lifecycle_buildpacks
+
+        CNBLifecycleDataModel.db.loggers.delete(logger)
+        sql = sqls.find { |s| s.include?('buildpack_lifecycle_buildpacks') }
+        expect(sql).to match(/ORDER BY .id./)
+      end
+    end
+
     describe '#stack' do
       it 'persists the stack' do
         lifecycle_data.stack = 'cflinuxfs4'