Merge pull request #12829 from iantropov/issue_insert_via_hmt_scope_3548

Fix insertion of records for hmt association with scope

Conflicts:
	activerecord/CHANGELOG.md

6 files changed, 32 insertions, 4 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 33c6f42988..abf6373030 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   Fix insertion of records via `has_many :through` association with scope.
+
+    Fixes #3548.
+
+    *Ivan Antropov*
+
 *   Auto-generate stable fixture UUIDs on PostgreSQL.
 
     Fixes: #11524
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 64bc98c642..c2eff0d8ce 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -83,12 +83,16 @@ 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 4d37ac6e2b..787f55e2e7 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -529,9 +529,9 @@ 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] }]
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 026a7fe635..6675e19dd9 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -1102,7 +1102,19 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     assert_equal [posts(:thinking)], person.reload.first_posts
   end
 
-  def test_has_many_through_with_includes_in_through_association_scope
+  test "has many through with includes in through association scope" do
     assert_not_empty posts(:welcome).author_address_extra_with_address
   end
+
+  test "insert records via has_many_through association with scope" do
+    club = Club.create!
+    member = Member.create!
+    Membership.create!(club: club, member: member)
+
+    club.favourites << member
+    assert_equal [member], club.favourites
+
+    club.reload
+    assert_equal [member], club.favourites
+  end
 end
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index 15611656fd..fb0b906c07 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -16,6 +16,10 @@ module ActiveRecord
       def self.connection
         Post.connection
       end
+
+      def self.table_name
+        'fake_table'
+      end
     end
 
     def test_construction
diff --git a/activerecord/test/models/club.rb b/activerecord/test/models/club.rb
index 566e0873f1..a762ad4bb5 100644
--- a/activerecord/test/models/club.rb
+++ b/activerecord/test/models/club.rb
@@ -6,6 +6,8 @@ class Club < ActiveRecord::Base
   has_one :sponsored_member, :through => :sponsor, :source => :sponsorable, :source_type => "Member"
   belongs_to :category
 
+  has_many :favourites, -> { where(memberships: { favourite: true }) }, through: :memberships, source: :member
+
   private
 
   def private_method