Switch SemanticLink to use new association

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

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 @@
   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 @@
 
     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