1 files changed, 193 insertions, 0 deletions
diff --git a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
new file mode 100644
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+++ b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
@@ -0,0 +1,193 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/post"
+require "models/comment"
+require "models/author"
+require "models/categorization"
+require "models/category"
+require "models/company"
+require "models/topic"
+require "models/reply"
+require "models/person"
+require "models/vertex"
+require "models/edge"
+
+class CascadedEagerLoadingTest < ActiveRecord::TestCase
+  fixtures :authors, :author_addresses, :mixins, :companies, :posts, :topics, :accounts, :comments,
+           :categorizations, :people, :categories, :edges, :vertices
+
+  def test_eager_association_loading_with_cascaded_two_levels
+    authors = Author.all.merge!(includes: { posts: :comments }, order: "authors.id").to_a
+    assert_equal 3, authors.size
+    assert_equal 5, authors[0].posts.size
+    assert_equal 3, authors[1].posts.size
+    assert_equal 10, authors[0].posts.collect { |post| post.comments.size }.inject(0) { |sum, i| sum + i }
+  end
+
+  def test_eager_association_loading_with_cascaded_two_levels_and_one_level
+    authors = Author.all.merge!(includes: [{ posts: :comments }, :categorizations], order: "authors.id").to_a
+    assert_equal 3, authors.size
+    assert_equal 5, authors[0].posts.size
+    assert_equal 3, authors[1].posts.size
+    assert_equal 10, authors[0].posts.collect { |post| post.comments.size }.inject(0) { |sum, i| sum + i }
+    assert_equal 1, authors[0].categorizations.size
+    assert_equal 2, authors[1].categorizations.size
+  end
+
+  def test_eager_association_loading_with_hmt_does_not_table_name_collide_when_joining_associations
+    authors = Author.joins(:posts).eager_load(:comments).where(posts: { tags_count: 1 }).to_a
+    assert_equal 3, assert_no_queries { authors.size }
+    assert_equal 10, assert_no_queries { authors[0].comments.size }
+  end
+
+  def test_eager_association_loading_grafts_stashed_associations_to_correct_parent
+    assert_equal people(:michael), Person.eager_load(primary_contact: :primary_contact).where("primary_contacts_people_2.first_name = ?", "Susan").order("people.id").first
+  end
+
+  def test_cascaded_eager_association_loading_with_join_for_count
+    categories = Category.joins(:categorizations).includes([{ posts: :comments }, :authors])
+
+    assert_equal 4, categories.count
+    assert_equal 4, categories.to_a.count
+    assert_equal 3, categories.distinct.count
+    assert_equal 3, categories.to_a.uniq.size # Must uniq since instantiating with inner joins will get dupes
+  end
+
+  def test_cascaded_eager_association_loading_with_duplicated_includes
+    categories = Category.includes(:categorizations).includes(categorizations: :author).where("categorizations.id is not null").references(:categorizations)
+    assert_nothing_raised do
+      assert_equal 3, categories.count
+      assert_equal 3, categories.to_a.size
+    end
+  end
+
+  def test_cascaded_eager_association_loading_with_twice_includes_edge_cases
+    categories = Category.includes(categorizations: :author).includes(categorizations: :post).where("posts.id is not null").references(:posts)
+    assert_nothing_raised do
+      assert_equal 3, categories.count
+      assert_equal 3, categories.to_a.size
+    end
+  end
+
+  def test_eager_association_loading_with_join_for_count
+    authors = Author.joins(:special_posts).includes([:posts, :categorizations])
+
+    assert_nothing_raised { authors.count }
+    assert_queries(3) { authors.to_a }
+  end
+
+  def test_eager_association_loading_with_cascaded_two_levels_with_two_has_many_associations
+    authors = Author.all.merge!(includes: { posts: [:comments, :categorizations] }, order: "authors.id").to_a
+    assert_equal 3, authors.size
+    assert_equal 5, authors[0].posts.size
+    assert_equal 3, authors[1].posts.size
+    assert_equal 10, authors[0].posts.collect { |post| post.comments.size }.inject(0) { |sum, i| sum + i }
+  end
+
+  def test_eager_association_loading_with_cascaded_two_levels_and_self_table_reference
+    authors = Author.all.merge!(includes: { posts: [:comments, :author] }, order: "authors.id").to_a
+    assert_equal 3, authors.size
+    assert_equal 5, authors[0].posts.size
+    assert_equal authors(:david).name, authors[0].name
+    assert_equal [authors(:david).name], authors[0].posts.collect { |post| post.author.name }.uniq
+  end
+
+  def test_eager_association_loading_with_cascaded_two_levels_with_condition
+    authors = Author.all.merge!(includes: { posts: :comments }, where: "authors.id=1", order: "authors.id").to_a
+    assert_equal 1, authors.size
+    assert_equal 5, authors[0].posts.size
+  end
+
+  def test_eager_association_loading_with_cascaded_three_levels_by_ping_pong
+    firms = Firm.all.merge!(includes: { account: { firm: :account } }, order: "companies.id").to_a
+    assert_equal 2, firms.size
+    assert_equal firms.first.account, firms.first.account.firm.account
+    assert_equal companies(:first_firm).account, assert_no_queries { firms.first.account.firm.account }
+    assert_equal companies(:first_firm).account.firm.account, assert_no_queries { firms.first.account.firm.account }
+  end
+
+  def test_eager_association_loading_with_has_many_sti
+    topics = Topic.all.merge!(includes: :replies, order: "topics.id").to_a
+    first, second, = topics(:first).replies.size, topics(:second).replies.size
+    assert_no_queries do
+      assert_equal first, topics[0].replies.size
+      assert_equal second, topics[1].replies.size
+    end
+  end
+
+  def test_eager_association_loading_with_has_many_sti_and_subclasses
+    reply = Reply.new(title: "gaga", content: "boo-boo", parent_id: 1)
+    assert reply.save
+
+    topics = Topic.all.merge!(includes: :replies, order: ["topics.id", "replies_topics.id"]).to_a
+    assert_no_queries do
+      assert_equal 2, topics[0].replies.size
+      assert_equal 0, topics[1].replies.size
+    end
+  end
+
+  def test_eager_association_loading_with_belongs_to_sti
+    replies = Reply.all.merge!(includes: :topic, order: "topics.id").to_a
+    assert_includes replies, topics(:second)
+    assert_not_includes replies, topics(:first)
+    assert_equal topics(:first), assert_no_queries { replies.first.topic }
+  end
+
+  def test_eager_association_loading_with_multiple_stis_and_order
+    author = Author.all.merge!(includes: { posts: [ :special_comments, :very_special_comment ] }, order: ["authors.name", "comments.body", "very_special_comments_posts.body"], where: "posts.id = 4").first
+    assert_equal authors(:david), author
+    assert_no_queries do
+      author.posts.first.special_comments
+      author.posts.first.very_special_comment
+    end
+  end
+
+  def test_eager_association_loading_of_stis_with_multiple_references
+    authors = Author.all.merge!(includes: { posts: { special_comments: { post: [ :special_comments, :very_special_comment ] } } }, order: "comments.body, very_special_comments_posts.body", where: "posts.id = 4").to_a
+    assert_equal [authors(:david)], authors
+    assert_no_queries do
+      authors.first.posts.first.special_comments.first.post.special_comments
+      authors.first.posts.first.special_comments.first.post.very_special_comment
+    end
+  end
+
+  def test_eager_association_loading_where_first_level_returns_nil
+    authors = Author.all.merge!(includes: { post_about_thinking: :comments }, order: "authors.id DESC").to_a
+    assert_equal [authors(:bob), authors(:mary), authors(:david)], authors
+    assert_no_queries do
+      authors[2].post_about_thinking.comments.first
+    end
+  end
+
+  def test_preload_through_missing_records
+    post = Post.where.not(author_id: Author.select(:id)).preload(author: { comments: :post }).first!
+    assert_no_queries { assert_nil post.author }
+  end
+
+  def test_eager_association_loading_with_missing_first_record
+    posts = Post.where(id: 3).preload(author: { comments: :post }).to_a
+    assert_equal posts.size, 1
+  end
+
+  def test_eager_association_loading_with_recursive_cascading_four_levels_has_many_through
+    source = Vertex.all.merge!(includes: { sinks: { sinks: { sinks: :sinks } } }, order: "vertices.id").first
+    assert_equal vertices(:vertex_4), assert_no_queries { source.sinks.first.sinks.first.sinks.first }
+  end
+
+  def test_eager_association_loading_with_recursive_cascading_four_levels_has_and_belongs_to_many
+    sink = Vertex.all.merge!(includes: { sources: { sources: { sources: :sources } } }, order: "vertices.id DESC").first
+    assert_equal vertices(:vertex_1), assert_no_queries { sink.sources.first.sources.first.sources.first.sources.first }
+  end
+
+  def test_eager_association_loading_with_cascaded_interdependent_one_level_and_two_levels
+    authors_relation = Author.all.merge!(includes: [:comments, { posts: :categorizations }], order: "authors.id")
+    authors = authors_relation.to_a
+    assert_equal 3, authors.size
+    assert_equal 10, authors[0].comments.size
+    assert_equal 1, authors[1].comments.size
+    assert_equal 5, authors[0].posts.size
+    assert_equal 3, authors[1].posts.size
+    assert_equal 3, authors[0].posts.collect { |post| post.categorizations.size }.inject(0) { |sum, i| sum + i }
+  end
+end