Feature skip_preload (#34)

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## master
 
+- [PR [#33](https://github.com/DmitryTsepelev/ar_lazy_preload/pull/34)] Feature skip_preload, allow turn automatic preload off ([@OuYangJinTing][])
+
 ## 0.3.1 (2020-07-10)
 
 - [PR [#33](https://github.com/DmitryTsepelev/ar_lazy_preload/pull/33)] Don't do merge if there is nothing to merge ([@Earendil95][])

README.md

@@ -44,6 +44,12 @@ ArLazyPreload.config.auto_preload = true
 
 After that there is no need to call `#lazy_preload` on the association, everything would be loaded lazily.
 
+If you want to turn automatic preload off for a specific record, you can call `.skip_preload` before any associations method:
+
+```ruby
+users.first.skip_preload.posts # => SELECT * FROM posts WHERE user_id = ?
+```
+
 ## Installation
 
 Add this line to your application's Gemfile, and you're all set:

lib/ar_lazy_preload/active_record/base.rb

@@ -10,5 +10,11 @@ def self.included(base)
     attr_accessor :lazy_preload_context
 
     delegate :try_preload_lazily, to: :lazy_preload_context, allow_nil: true
+
+    def skip_preload
+      lazy_preload_context&.records&.delete(self)
+      self.lazy_preload_context = nil
+      self
+    end
   end
 end

lib/ar_lazy_preload/active_record/collection_association.rb

@@ -3,7 +3,7 @@
 module ArLazyPreload
   # ActiveRecord::CollectionAssociation patch with a hook for lazy preloading
   module CollectionAssociation
-    # rubocop:disable Metrics/AbcSize
+    # rubocop:disable Metrics/AbcSize, Metrics/CyclomaticComplexity
     def ids_reader
       return super if owner.lazy_preload_context.blank?
 
@@ -16,6 +16,6 @@ def ids_reader
         @association_ids ||= reader.map(&primary_key)
       end
     end
-    # rubocop:enable Metrics/AbcSize
+    # rubocop:enable Metrics/AbcSize, Metrics/CyclomaticComplexity
   end
 end

spec/ar_lazy_preload/active_record/base_spec.rb

@@ -3,9 +3,15 @@
 require "spec_helper"
 
 describe ArLazyPreload::Base do
-  describe "lazy_preload" do
+  describe "#lazy_preload" do
     subject { ActiveRecord::Base }
 
     it { is_expected.to respond_to(:lazy_preload) }
   end
+
+  describe "#skip_preload" do
+    subject { User.new }
+
+    it { is_expected.to respond_to(:skip_preload) }
+  end
 end

spec/ar_lazy_preload/skip_preload_spec.rb

@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+describe "ArLazyPreload.skip_preload" do
+  let!(:user1) { create(:user) }
+  let!(:user2) { create(:user) }
+  let!(:user3) { create(:user) }
+
+  let!(:post1) { create(:post, user: user1) }
+  let!(:post2) { create(:post, user: user1) }
+  let!(:post3) { create(:post, user: user2) }
+
+  before(:each) { ArLazyPreload.config.auto_preload = true }
+
+  describe "#skip_preload" do
+    subject { User.all }
+
+    it "after skip preload, changed lazy preload context" do
+      subject.load.last.skip_preload
+      expect(subject.last.lazy_preload_context).to be(nil)
+      expect(subject.first.lazy_preload_context.records).not_to include(subject.last)
+    end
+
+    it "only load own association" do
+      subject.each do |user|
+        # SELECT "posts".* FROM "posts" WHERE "posts"."user_id" = ?
+        expect do
+          user.skip_preload.posts.load
+        end.to make_database_queries(matching: "\"posts\".\"user_id\" = ?")
+      end
+    end
+
+    it "loads excluded association" do
+      subject.load.last.skip_preload.posts.to_a
+      id_concat = subject[0..-2].map(&:id).join(", ")
+      question_concat = (["?"] * (subject.size - 1)).join(", ")
+      expect do
+        subject.first.posts.to_a
+      end.to make_database_queries(
+        matching: /\"user_id\" IN ([(#{id_concat})|(#{question_concat})])/
+      )
+    end
+  end
+end