Fix insertion of records for hmt association with scope, fix #3548

2 files changed, 7 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index 31b8d27892..53268372eb 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -84,12 +84,16 @@ module ActiveRecord
           @through_records[record.object_id] ||= begin
             ensure_mutable
 
-            through_record = through_association.build
+            through_record = through_association.build through_scope_attributes
             through_record.send("#{source_reflection.name}=", record)
             through_record
           end
         end
 
+        def through_scope_attributes
+          scope.where_values_hash(through_association.reflection.name.to_s)
+        end
+
         def save_through_record(record)
           build_through_record(record).save!
         ensure
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 6e0669a77f..5e38ed632d 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -527,9 +527,9 @@ module ActiveRecord
     #
     #   User.where(name: 'Oscar').where_values_hash
     #   # => {name: "Oscar"}
-    def where_values_hash
+    def where_values_hash(relation_table_name = table_name)
       equalities = where_values.grep(Arel::Nodes::Equality).find_all { |node|
-        node.left.relation.name == table_name
+        node.left.relation.name == relation_table_name
       }
 
       binds = Hash[bind_values.find_all(&:first).map { |column, v| [column.name, v] }]