Add relation between Goal and LocalTarget

This is similar to what we do with investments, which belong to a heading
but also belong to a budget. In our case, the reason is we've been asked
to add local targets which belong to a goal but are not related to any
existing target.
Even though we're not implementing that case right now, we're adding the
relation so we don't have to add data migrations in the future.

app/models/sdg/goal.rb

@@ -4,6 +4,7 @@ class SDG::Goal < ApplicationRecord
   validates :code, presence: true, uniqueness: true, inclusion: { in: 1..17 }
 
   has_many :targets, dependent: :destroy
+  has_many :local_targets, dependent: :destroy
 
   def title
     I18n.t("sdg.goals.goal_#{code}.title")

app/models/sdg/local_target.rb

@@ -2,8 +2,6 @@ class SDG::LocalTarget < ApplicationRecord
   include Comparable
   include SDG::Related
 
-  delegate :goal, to: :target
-
   translates :title, touch: true
   translates :description, touch: true
   include Globalizable
@@ -14,8 +12,12 @@ class SDG::LocalTarget < ApplicationRecord
   validates :code, presence: true, uniqueness: true,
     format: ->(local_target) { /\A#{local_target.target&.code}\.\d+/ }
   validates :target, presence: true
+  validates :goal, presence: true
 
   belongs_to :target
+  belongs_to :goal
+
+  before_validation :set_related_goal
 
   def self.[](code)
     find_by!(code: code)
@@ -40,4 +42,8 @@ class SDG::LocalTarget < ApplicationRecord
     def subcode
       code.split(".").last
     end
+
+    def set_related_goal
+      self.goal ||= target&.goal
+    end
 end

db/migrate/20210123100638_add_goals_to_local_targets.rb

@@ -0,0 +1,5 @@
+class AddGoalsToLocalTargets < ActiveRecord::Migration[5.2]
+  def change
+    add_reference :sdg_local_targets, :goal
+  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.define(version: 2021_01_07_125458) do
+ActiveRecord::Schema.define(version: 2021_01_23_100638) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_trgm"
@@ -1322,7 +1322,9 @@ ActiveRecord::Schema.define(version: 2021_01_07_125458) do
     t.string "code"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "goal_id"
     t.index ["code"], name: "index_sdg_local_targets_on_code", unique: true
+    t.index ["goal_id"], name: "index_sdg_local_targets_on_goal_id"
     t.index ["target_id"], name: "index_sdg_local_targets_on_target_id"
   end
 

spec/factories/sdg.rb

@@ -13,6 +13,7 @@ FactoryBot.define do
     sequence(:description) { |n| "Help for Local Target #{n}" }
 
     target { SDG::Target[code.rpartition(".").first] }
+    goal { SDG::Goal[code.split(".")[0]] }
   end
 
   factory :sdg_phase, class: "SDG::Phase" do

spec/models/sdg/local_target_spec.rb

@@ -18,7 +18,7 @@ describe SDG::LocalTarget do
   end
 
   it "is not valid without a code" do
-    expect(build(:sdg_local_target, code: nil, target: SDG::Target[1.1])).not_to be_valid
+    expect(build(:sdg_local_target, code: nil, target: SDG::Target[1.1], goal: SDG::Goal[1])).not_to be_valid
   end
 
   it "is not valid when code does not include associated target code" do
@@ -47,6 +47,15 @@ describe SDG::LocalTarget do
     expect(build(:sdg_local_target, target: nil)).not_to be_valid
   end
 
+  describe "#set_related_goal" do
+    it "before validation set related goal" do
+      local_target = build(:sdg_local_target, code: "1.1.1", target: SDG::Target["1.1"], goal: nil)
+
+      expect(local_target).to be_valid
+      expect(local_target.goal).to eq(SDG::Goal[1])
+    end
+  end
+
   describe "#goal" do
     it "returns the target goal" do
       local_target = create(:sdg_local_target, code: "1.1.1")