I haven't looked into how hard this would be to fix, but:
Named scopes don't handle :finder_sql associations well.
I've attached a failing test as a diff. The interesting bits:
class Author < ActiveRecord::Base
has_many :posts
has_many :posts_with_finder_sql, :class_name => "Post", :finder_sql => 'SELECT * FROM posts WHERE author_id = #{id}'
end
class Post < ActiveRecord::Base
named_scope :containing_the_letter_a, :conditions => "body LIKE '%a%'"
end
# Sanity check
assert_equal authors(:david).posts, authors(:david).posts_with_finder_sql
# Currently fails: the latter returns nil
assert_equal authors(:david).posts.containing_the_letter_a,
authors(:david).posts_with_finder_sql.containing_the_letter_a
