Make scope arity check consistent (#36134)

* Make scope arity check consistent

* Add test for arity change

[Rob Trame + Rafael Mendonça França]

2 files changed, 19 insertions, 0 deletions

diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index b865002f03..49bcb1d010 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -1516,6 +1516,24 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_match message, error.message
   end
 
+  test "preloading and eager loading of optional instance dependent associations is not supported" do
+    message = "association scope 'posts_mentioning_author' is"
+    error = assert_raises(ArgumentError) do
+      Author.includes(:posts_mentioning_author).to_a
+    end
+    assert_match message, error.message
+
+    error = assert_raises(ArgumentError) do
+      Author.preload(:posts_mentioning_author).to_a
+    end
+    assert_match message, error.message
+
+    error = assert_raises(ArgumentError) do
+      Author.eager_load(:posts_mentioning_author).to_a
+    end
+    assert_match message, error.message
+  end
+
   test "preload with invalid argument" do
     exception = assert_raises(ArgumentError) do
       Author.preload(10).to_a
diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index 67be59a1fe..b52b643ad7 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -153,6 +153,7 @@ class Author < ActiveRecord::Base
   has_many :comments_on_posts_with_default_include, through: :posts_with_default_include, source: :comments
 
   has_many :posts_with_signature, ->(record) { where("posts.title LIKE ?", "%by #{record.name.downcase}%") }, class_name: "Post"
+  has_many :posts_mentioning_author, ->(record = nil) { where("posts.body LIKE ?", "%#{record&.name&.downcase}%") }, class_name: "Post"
 
   has_many :posts_with_extension, -> { order(:title) }, class_name: "Post" do
     def extension_method; end