Apply default scope when joining associations.

For example:

    class Post < ActiveRecord::Base
      default_scope -> { where published: true }
    end

    class Comment
      belongs_to :post
    end

When calling `Comment.join(:post)`, we expect to receive only
comments on published posts, since that is the default scope for
posts.

Before this change, the default scope from `Post` was not applied,
so we'd get comments on unpublished posts.

1 files changed, 2 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/associations/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
index b81aecb4e5..e0715d9dd1 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -106,6 +106,8 @@ module ActiveRecord
               ]
             end
 
+            scope_chain_items += [reflection.klass.send(:build_default_scope)].compact
+
             constraint = scope_chain_items.inject(constraint) do |chain, item|
               unless item.is_a?(Relation)
                 item = ActiveRecord::Relation.new(reflection.klass, table).instance_exec(self, &item)