The Association Relation should use `empty?` and `size` from Relation.

968c581ea34b5236af14805e6a77913b1cb36238 have introduced this bug #14744
on Association Relation when the method `empty?` or `size` was called.

Example:
  # Given an author that does have 3 posts, but none of them with the
  # title 'Some Title'
  Author.last.posts.where(title: 'Some Title').size
  # => 3

It was occurring, because the Association Relation had implemented these
methods based on `@association`, this way giving wrong results.

To fix it, was necessary to remove the methods `empty?` and `size` from
Association Relation. It just have to use these methods from Relation.

Example:
  # Given an author that does have 3 posts, but none of them with the
  # title 'Some Title'
  Author.last.posts.where(title: 'Some Title').size
  # => 0
  # Now it will return the correct value.

Fixes #14744.

2 files changed, 11 insertions, 8 deletions

diff --git a/activerecord/lib/active_record/association_relation.rb b/activerecord/lib/active_record/association_relation.rb
index 45f1b07f69..5a84792f45 100644
--- a/activerecord/lib/active_record/association_relation.rb
+++ b/activerecord/lib/active_record/association_relation.rb
@@ -9,14 +9,6 @@ module ActiveRecord
       @association
     end
 
-    def size
-      @association.size
-    end
-
-    def empty?
-      @association.empty?
-    end
-
     def ==(other)
       other == to_a
     end
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 562cfe6796..ddfcaaf986 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -864,6 +864,17 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal 9, posts.where(:comments_count => 0).count
   end
 
+  def test_count_on_association_relation
+    author = Author.last
+    another_author = Author.first
+    posts = Post.where(author_id: author.id)
+
+    assert_equal author.posts.where(author_id: author.id).size, posts.count
+
+    assert_equal 0, author.posts.where(author_id: another_author.id).size
+    assert author.posts.where(author_id: another_author.id).empty?
+  end
+
   def test_count_with_distinct
     posts = Post.all