Fix eager loading associations with string joins not to raise NoMethodError

Fixes #34456.

3 files changed, 23 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/associations/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
index ca0305abbb..6a7e92dc28 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -44,8 +44,7 @@ module ActiveRecord
 
             unless others.empty?
               joins.concat arel.join_sources
-              right = joins.last.right
-              right.expr.children.concat(others)
+              append_constraints(joins.last, others)
             end
 
             # The current table in this iteration becomes the foreign table in the next
@@ -65,6 +64,16 @@ module ActiveRecord
 
           @readonly = reflection.scope && reflection.scope_for(base_klass.unscoped).readonly_value
         end
+
+        private
+          def append_constraints(join, constraints)
+            if join.is_a?(Arel::Nodes::StringJoin)
+              join_string = table.create_and(constraints.unshift(join.left))
+              join.left = Arel.sql(base_klass.connection.visitor.compile(join_string))
+            else
+              join.right.expr.children.concat(constraints)
+            end
+          end
       end
     end
   end
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index 49bcb1d010..9ed25ca7c2 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -101,6 +101,17 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_equal [taggings(:normal_comment_rating)], rating.taggings_without_tag
   end
 
+  def test_loading_association_with_string_joins
+    rating = Rating.first
+    assert_equal [taggings(:normal_comment_rating)], rating.taggings_with_no_tag
+
+    rating = Rating.preload(:taggings_with_no_tag).first
+    assert_equal [taggings(:normal_comment_rating)], rating.taggings_with_no_tag
+
+    rating = Rating.eager_load(:taggings_with_no_tag).first
+    assert_equal [taggings(:normal_comment_rating)], rating.taggings_with_no_tag
+  end
+
   def test_loading_with_scope_including_joins
     member = Member.first
     assert_equal members(:groucho), member
diff --git a/activerecord/test/models/rating.rb b/activerecord/test/models/rating.rb
index 49aa38285f..2a18ea45ac 100644
--- a/activerecord/test/models/rating.rb
+++ b/activerecord/test/models/rating.rb
@@ -4,4 +4,5 @@ class Rating < ActiveRecord::Base
   belongs_to :comment
   has_many :taggings, as: :taggable
   has_many :taggings_without_tag, -> { left_joins(:tag).where("tags.id": nil) }, as: :taggable, class_name: "Tagging"
+  has_many :taggings_with_no_tag, -> { joins("LEFT OUTER JOIN tags ON tags.id = taggings.tag_id").where("tags.id": nil) }, as: :taggable, class_name: "Tagging"
 end