Merge pull request #18383 from scambra/habtm-with-where-includes-16032-for-master

Includes HABTM returns correct size now

3 files changed, 40 insertions, 1 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 5e523d2aa6..7055cb2e25 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,22 @@
+*   Includes HABTM returns correct size now. It's caused by the join dependency
+    only instantiates one HABTM object because the join table hasn't a primary key.
+
+    Fixes #16032.
+
+    Examples:
+
+        before:
+
+        Project.first.salaried_developers.size # => 3
+        Project.includes(:salaried_developers).first.salaried_developers.size # => 1
+
+        after:
+
+        Project.first.salaried_developers.size # => 3
+        Project.includes(:salaried_developers).first.salaried_developers.size # => 3
+
+    *Bigxiang*
+
 *   Add option to index errors in nested attributes
 
     For models which have nested attributes, errors within those models will
diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index ca473beea3..0e98a3b3a4 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -150,7 +150,8 @@ module ActiveRecord
 
         message_bus.instrument('instantiation.active_record', payload) do
           result_set.each { |row_hash|
-            parent = parents[row_hash[primary_key]] ||= join_root.instantiate(row_hash, column_aliases)
+            parent_key = primary_key ? row_hash[primary_key] : row_hash
+            parent = parents[parent_key] ||= join_root.instantiate(row_hash, column_aliases)
             construct(parent, join_root, row_hash, result_set, seen, model_cache, aliases)
           }
         end
diff --git a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
index 20af436e02..e9f679e6de 100644
--- a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
@@ -957,4 +957,23 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     projects = ProjectUnscopingDavidDefaultScope.includes(:developers).where(id: project.id)
     assert_equal 1, projects.first.developers.size
   end
+
+  def test_preloaded_associations_size
+    assert_equal Project.first.salaried_developers.size,
+      Project.preload(:salaried_developers).first.salaried_developers.size
+
+    assert_equal Project.includes(:salaried_developers).references(:salaried_developers).first.salaried_developers.size,
+      Project.preload(:salaried_developers).first.salaried_developers.size
+
+    # Nested HATBM
+    first_project = Developer.first.projects.first
+    preloaded_first_project =
+      Developer.preload(projects: :salaried_developers).
+        first.
+        projects.
+        detect { |p| p.id == first_project.id }
+
+    assert preloaded_first_project.salaried_developers.loaded?, true
+    assert_equal first_project.salaried_developers.size, preloaded_first_project.salaried_developers.size
+  end
 end