Fixed HABTM's CollectionAssociation size

HABTM should fall back to using the normal CollectionAssociation's size calculation if the collection is not cached or loaded.

This addresses both #14913 and #14914 for master.

2 files changed, 20 insertions, 0 deletions

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 5d33634da2..c166fe87e8 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
@@ -217,6 +217,24 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     assert_equal developers(:poor_jamis, :jamis, :david), projects(:active_record).developers
   end
 
+  def test_habtm_collection_size_from_build
+    devel = Developer.create("name" => "Fred Wu")
+    devel.projects << Project.create("name" => "Grimetime")
+    devel.projects.build
+
+    assert_equal 2, devel.projects.size
+  end
+
+  def test_habtm_collection_size_from_params
+    devel = Developer.new({
+      projects_attributes: {
+        '0' => {}
+      }
+    })
+
+    assert_equal 1, devel.projects.size
+  end
+
   def test_build
     devel = Developer.find(1)
     proj = assert_no_queries { devel.projects.build("name" => "Projekt") }
diff --git a/activerecord/test/models/developer.rb b/activerecord/test/models/developer.rb
index 762259ffa3..0a614c3bfd 100644
--- a/activerecord/test/models/developer.rb
+++ b/activerecord/test/models/developer.rb
@@ -13,6 +13,8 @@ class Developer < ActiveRecord::Base
     end
   end
 
+  accepts_nested_attributes_for :projects
+
   has_and_belongs_to_many :projects_extended_by_name,
       -> { extending(DeveloperProjectsAssociationExtension) },
       :class_name => "Project",