Association loading isn't to be affected by scoping consistently

Follow-up of 5c71000, #29834, and #30271.

Currently, preloading and eager loading are not to be affected by
scoping, with the exception of `unscoped`.

But non eager loaded association access is still affected by scoping.

Although this is a breaking change, the association loading will work
consistently whether preloaded / eager loaded or not.

Before:

```ruby
Post.where("1=0").scoping do
  Comment.find(1).post                   # => nil
  Comment.preload(:post).find(1).post    # => #<Post id: 1, ...>
  Comment.eager_load(:post).find(1).post # => #<Post id: 1, ...>
end
```

After:

```ruby
Post.where("1=0").scoping do
  Comment.find(1).post                   # => #<Post id: 1, ...>
  Comment.preload(:post).find(1).post    # => #<Post id: 1, ...>
  Comment.eager_load(:post).find(1).post # => #<Post id: 1, ...>
end
```

Fixes #34638.
Fixes #35398.

1 files changed, 18 insertions, 5 deletions

diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index cd9c8a5285..594d161fa3 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -1400,11 +1400,24 @@ class EagerAssociationTest < ActiveRecord::TestCase
     assert_equal expected, FirstPost.unscoped.find(2)
   end
 
-  test "preload ignores the scoping" do
-    assert_equal(
-      Comment.find(1).post,
-      Post.where("1 = 0").scoping { Comment.preload(:post).find(1).post }
-    )
+  test "belongs_to association ignores the scoping" do
+    post = Comment.find(1).post
+
+    Post.where("1=0").scoping do
+      assert_equal post, Comment.find(1).post
+      assert_equal post, Comment.preload(:post).find(1).post
+      assert_equal post, Comment.eager_load(:post).find(1).post
+    end
+  end
+
+  test "has_many association ignores the scoping" do
+    comments = Post.find(1).comments.to_a
+
+    Comment.where("1=0").scoping do
+      assert_equal comments, Post.find(1).comments
+      assert_equal comments, Post.preload(:comments).find(1).comments
+      assert_equal comments, Post.eager_load(:comments).find(1).comments
+    end
   end
 
   test "deep preload" do