Switch SemanticLink to use new association

And ActiveRecord magic does the rest when used correctly.

app/jobs/backorder_job.rb

@@ -13,7 +13,7 @@ class BackorderJob < ApplicationJob
   sidekiq_options retry: 0
 
   def self.check_stock(order)
-    links = SemanticLink.where(variant_id: order.line_items.select(:variant_id))
+    links = SemanticLink.where(subject: order.variants)
 
     perform_later(order) if links.exists?
   rescue StandardError => e

app/jobs/stock_sync_job.rb

@@ -36,7 +36,7 @@ class StockSyncJob < ApplicationJob
 
   def self.catalog_ids(order)
     stock_controlled_variants = order.variants.reject(&:on_demand)
-    links = SemanticLink.where(variant_id: stock_controlled_variants.map(&:id))
+    links = SemanticLink.where(subject: stock_controlled_variants)
     semantic_ids = links.pluck(:semantic_id)
     semantic_ids.map do |product_id|
       FdcUrlBuilder.new(product_id).catalog_url

app/models/semantic_link.rb

@@ -2,8 +2,9 @@
 
 # Link a Spree::Variant to an external DFC SuppliedProduct.
 class SemanticLink < ApplicationRecord
+  self.ignored_columns += [:variant_id]
+
   belongs_to :subject, polymorphic: true
-  belongs_to :variant, class_name: "Spree::Variant"
 
   validates :semantic_id, presence: true
 end

app/models/spree/variant.rb

@@ -60,7 +60,7 @@ module Spree
     has_many :exchanges, through: :exchange_variants
     has_many :variant_overrides, dependent: :destroy
     has_many :inventory_items, dependent: :destroy
-    has_many :semantic_links, dependent: :delete_all
+    has_many :semantic_links, as: :subject, dependent: :delete_all
     has_many :supplier_properties, through: :supplier, source: :properties
 
     localize_number :price, :weight

db/migrate/20241030033956_change_null_on_semantic_links.rb

@@ -0,0 +1,8 @@
+class ChangeNullOnSemanticLinks < ActiveRecord::Migration[7.0]
+  def change
+    change_column_null :semantic_links, :subject_id, false
+    change_column_null :semantic_links, :subject_type, false
+
+    change_column_null :semantic_links, :variant_id, true
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2024_10_30_023153) do
+ActiveRecord::Schema[7.0].define(version: 2024_10_30_033956) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_stat_statements"
   enable_extension "plpgsql"
@@ -401,12 +401,12 @@ ActiveRecord::Schema[7.0].define(version: 2024_10_30_023153) do
   end
 
   create_table "semantic_links", force: :cascade do |t|
-    t.bigint "variant_id", null: false
+    t.bigint "variant_id"
     t.string "semantic_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
-    t.string "subject_type"
-    t.bigint "subject_id"
+    t.string "subject_type", null: false
+    t.bigint "subject_id", null: false
     t.index ["subject_type", "subject_id"], name: "index_semantic_links_on_subject"
     t.index ["variant_id"], name: "index_semantic_links_on_variant_id"
   end

spec/migrations/20241030025540_copy_subject_on_semantic_links_spec.rb

@@ -10,10 +10,10 @@ RSpec.describe CopySubjectOnSemanticLinks do
 
     it "copies the original data" do
       link = SemanticLink.create!(
-        variant: original_variant,
         subject: dummy_variant, # This would be NULL when migration runs.
         semantic_id: "some-url",
       )
+      SemanticLink.update_all("variant_id = #{original_variant.id}")
 
       expect { subject.up }.to change {
         link.reload.subject

spec/models/semantic_link_spec.rb

@@ -4,6 +4,5 @@ require 'spec_helper'
 
 RSpec.describe SemanticLink, type: :model do
   it { is_expected.to belong_to :subject }
-  it { is_expected.to belong_to :variant }
   it { is_expected.to validate_presence_of(:semantic_id) }
 end