Restrict deletion of adjustment reasons if adjustments present

.rubocop_todo.yml

@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2025-06-26 11:28:28 UTC using RuboCop version 1.76.0.
+# on 2025-07-08 12:12:57 UTC using RuboCop version 1.76.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
@@ -332,7 +332,7 @@ Rails/FilePath:
     - "core/lib/spree/testing_support/dummy_app.rb"
     - "sample/lib/spree/sample.rb"
 
-# Offense count: 43
+# Offense count: 42
 # Configuration parameters: Include.
 # Include: **/app/models/**/*.rb
 Rails/HasManyOrHasOneDependent:

core/app/models/spree/adjustment_reason.rb

@@ -2,7 +2,7 @@
 
 module Spree
   class AdjustmentReason < Spree::Base
-    has_many :adjustments, inverse_of: :adjustment_reason
+    has_many :adjustments, inverse_of: :adjustment_reason, dependent: :restrict_with_error
 
     validates :name, presence: true, uniqueness: { case_sensitive: false, allow_blank: true }
     validates :code, presence: true, uniqueness: { case_sensitive: false, allow_blank: true }

core/db/migrate/20250708120317_add_adjustment_reason_foreign_keys.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+class AddAdjustmentReasonForeignKeys < ActiveRecord::Migration[7.0]
+  def up
+    # Uncomment the following code to remove orphaned records if this migration fails
+    #
+    # say_with_time "Removing invalid adjustment reason IDs from adjustments table" do
+    #   Spree::Adjustment.where.not(adjustment_reason_id: nil).left_joins(:adjustment_reason).where(spree_adjustment_reasons: { id: nil }).update_all(adjustment_reason_id: nil)
+    # end
+
+    add_foreign_key :spree_adjustments, :spree_adjustment_reasons, column: :adjustment_reason_id, null: true, on_delete: :restrict
+  rescue ActiveRecord::StatementInvalid => e
+    if e.cause.is_a?(PG::ForeignKeyViolation) || e.cause.is_a?(Mysql2::Error) || e.cause.is_a?(SQLite3::ConstraintException)
+      Rails.logger.warn <<~MSG
+        ⚠️ Foreign key constraint failed when adding :spree_adjustments => :spree_adjustment_reasons.
+        To fix this:
+          1. Uncomment the code that removes invalid adjustment reason IDs from the spree_adjustments table.
+          2. Rerun the migration.
+        Offending error: #{e.cause.class} - #{e.cause.message}
+      MSG
+    end
+    raise
+  end
+
+  def down
+    remove_foreign_key :spree_adjustments, :spree_adjustment_reasons, column: :adjustment_reason_id, null: true, on_delete: :restrict
+  end
+end