Extract common eager loading parameters into Class

This helps keep the duplication down.

app/controllers/alchemy/admin/pages_controller.rb

@@ -404,20 +404,7 @@ def set_preview_mode
       end
 
       def page_includes
-        {
-          :tags,
-          language: :site,
-          draft_version: {
-            elements: [
-              :page,
-              :touchable_pages,
-              {
-                ingredients: :related_object,
-                contents: :essence,
-              },
-            ],
-          },
-        }
+        Alchemy::EagerLoading.page_includes(version: :draft_version)
       end
     end
   end

app/controllers/alchemy/pages_controller.rb

@@ -246,20 +246,7 @@ def page_not_found!
     end
 
     def page_includes
-      {
-        :tags,
-        language: :site,
-        public_version: {
-          elements: [
-            :page,
-            :touchable_pages,
-            {
-              ingredients: :related_object,
-              contents: :essence,
-            },
-          ],
-        },
-      }
+      Alchemy::EagerLoading.page_includes(version: :public_version)
     end
   end
 end

app/jobs/alchemy/publish_page_job.rb

@@ -6,18 +6,7 @@ class PublishPageJob < BaseJob
 
     def perform(page_id, public_on:)
       page = Alchemy::Page.includes(
-        :tags,
-        language: :site,
-        draft_version: {
-          elements: [
-            :page,
-            :touchable_pages,
-            {
-              ingredients: :related_object,
-              contents: :essence,
-            },
-          ],
-        },
+        Alchemy::EagerLoading.page_includes(version: :draft_version)
       ).find(page_id)
       Alchemy::Page::Publisher.new(page).publish!(public_on: public_on)
     end

app/models/alchemy/eager_loading.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+module Alchemy
+  # Eager loading parameters for loading pages
+  class EagerLoading
+    PAGE_VERSIONS = %i[draft_version public_version]
+
+    class << self
+      # Eager loading parameters for {ActiveRecord::Base.includes}
+      #
+      # Pass this to +includes+ whereever you load an {Alchemy::Page}
+      #
+      #     Alchemy::Page.includes(Alchemy::EagerLoading.page_includes).find_by(urlname: "my-page")
+      #
+      # @param version [Symbol] Type of page version to eager load
+      # @return [Array]
+      def page_includes(version: :public_version)
+        raise UnsupportedPageVersion unless version.in? PAGE_VERSIONS
+
+        [
+          :tags,
+          {
+            language: :site,
+            version => {
+              elements: [
+                :page,
+                :touchable_pages,
+                {
+                  ingredients: :related_object,
+                  contents: :essence,
+                },
+              ],
+            },
+          },
+        ]
+      end
+    end
+  end
+end

lib/alchemy/errors.rb

@@ -11,15 +11,15 @@ class DefaultLanguageNotFoundError < StandardError
     # Raised if no default language configuration can be found.
     def message
       "No default language configuration found!" \
-        " Please ensure that you have a 'default_language' defined in Alchemy configuration file."
+      " Please ensure that you have a 'default_language' defined in Alchemy configuration file."
     end
   end
 
   class DefaultSiteNotFoundError < StandardError
     # Raised if no default site configuration can be found.
     def message
       "No default site configuration found!" \
-        " Please ensure that you have a 'default_site' defined in Alchemy configuration file."
+      " Please ensure that you have a 'default_site' defined in Alchemy configuration file."
     end
   end
 
@@ -90,4 +90,10 @@ def message
       "You need to provide a current_user method in your ApplicationController that returns the current authenticated user."
     end
   end
+
+  class UnsupportedPageVersion < StandardError
+    def message
+      "Unknown Version! Please use one of #{Alchemy::EagerLoading::PAGE_VERSIONS.join(", ")}"
+    end
+  end
 end

spec/models/alchemy/eager_loading_spec.rb

@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+RSpec.describe Alchemy::EagerLoading do
+  describe ".page_includes" do
+    context "with no version param given" do
+      subject { described_class.page_includes }
+
+      it "returns public version includes" do
+        is_expected.to match_array([
+          :tags,
+          {
+            language: :site,
+            public_version: {
+              elements: [
+                :page,
+                :touchable_pages,
+                {
+                  ingredients: :related_object,
+                  contents: :essence,
+                },
+              ],
+            },
+          },
+        ])
+      end
+    end
+
+    context "with version param given" do
+      subject { described_class.page_includes(version: :draft_version) }
+
+      it "returns version includes" do
+        is_expected.to match_array([
+          :tags,
+          {
+            language: :site,
+            draft_version: {
+              elements: [
+                :page,
+                :touchable_pages,
+                {
+                  ingredients: :related_object,
+                  contents: :essence,
+                },
+              ],
+            },
+          },
+        ])
+      end
+    end
+
+    context "with unknown version param given" do
+      subject { described_class.page_includes(version: :foo_baz) }
+
+      it "returns version includes" do
+        expect { subject }.to raise_error(Alchemy::UnsupportedPageVersion)
+      end
+    end
+  end
+end