Merge pull request #13550 from vipulnsward/13437-fix

Fix for #13437

Conflicts:
	activerecord/CHANGELOG.md

3 files changed, 22 insertions, 1 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 4fdeae70d2..b5d3420dd7 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Fixed regression on preload/includes with multiple arguments failing in certain conditions,
+    raising a NoMethodError internally by calling `reflect_on_association` for `NilClass:Class`.
+
+    Fixes #13437.
+
+    *Vipul A M*, *khustochka*
+
 *   Add the ability to nullify the `enum` column.
 
      Example:
diff --git a/activerecord/lib/active_record/associations/preloader.rb b/activerecord/lib/active_record/associations/preloader.rb
index 2393667ac8..83637a0409 100644
--- a/activerecord/lib/active_record/associations/preloader.rb
+++ b/activerecord/lib/active_record/associations/preloader.rb
@@ -183,7 +183,7 @@ module ActiveRecord
         def run(preloader); end
 
         def preloaded_records
-          owners.flat_map { |owner| owner.read_attribute reflection.name }
+          owners.flat_map { |owner| owner.association(reflection.name).target }
         end
       end
 
diff --git a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
index 811d91f849..904d85266e 100644
--- a/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
+++ b/activerecord/test/cases/associations/cascaded_eager_loading_test.rb
@@ -174,4 +174,18 @@ class CascadedEagerLoadingTest < ActiveRecord::TestCase
     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")
+    assert_nothing_raised do
+      authors_relation.to_a
+    end
+    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