Merge pull request #7661 from ernie/build-join-records-on-unsaved-hmt

Fix collection= on hm:t join models when unsaved

3 files changed, 25 insertions, 0 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 60eb1abdb6..b3c1b034d7 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,11 @@
 ## Rails 3.2.9 (unreleased)
 
+*   Fix creation of through association models when using `collection=[]`
+    on a `has_many :through` association from an unsaved model.
+    Fix #7661.
+
+    *Ernie Miller*
+
 *   Explain only normal CRUD sql (select / update / insert / delete).
     Fix problem that explains unexplainable sql. Closes #7544 #6458.
 
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 53d49fef2e..ce81333aa9 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -38,6 +38,20 @@ module ActiveRecord
         super
       end
 
+      def concat_records(records)
+        ensure_not_nested
+
+        records = super
+
+        if owner.new_record? && records
+          records.flatten.each do |record|
+            build_through_record(record)
+          end
+        end
+
+        records
+      end
+
       def insert_record(record, validate = true, raise = false)
         ensure_not_nested
 
diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index 4489c3e638..e4710eb61b 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -845,6 +845,11 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_assign_array_to_new_record_builds_join_records
+    c = Category.new(:name => 'Fishing', :authors => [Author.first])
+    assert_equal 1, c.categorizations.size
+  end
+
   def test_create_bang_should_raise_exception_when_join_record_has_errors
     repair_validations(Categorization) do
       Categorization.validate { |r| r.errors[:base] << 'Invalid Categorization' }