Fix deleting through records when using has_many through with `source_type`

Currently deleting through records doesn't respect `source_type`. It
should not be ignored in that case.

Related #23209.
Fixes #24116.

activerecord/lib/active_record/associations/through_association.rb

@@ -38,24 +38,22 @@ def target_scope
         def construct_join_attributes(*records)
           ensure_mutable
 
-          if source_reflection.association_primary_key(reflection.klass) == reflection.klass.primary_key
+          association_primary_key = source_reflection.association_primary_key(reflection.klass)
+
+          if association_primary_key == reflection.klass.primary_key && !options[:source_type]
             join_attributes = { source_reflection.name => records }
           else
             join_attributes = {
-              source_reflection.foreign_key =>
-                records.map { |record|
-                  record.send(source_reflection.association_primary_key(reflection.klass))
-                }
+              source_reflection.foreign_key => records.map(&association_primary_key.to_sym)
             }
           end
 
           if options[:source_type]
-            join_attributes[source_reflection.foreign_type] =
-              records.map { |record| record.class.base_class.name }
+            join_attributes[source_reflection.foreign_type] = [ options[:source_type] ]
           end
 
           if records.count == 1
-            Hash[join_attributes.map { |k, v| [k, v.first] }]
+            join_attributes.transform_values!(&:first)
           else
             join_attributes
           end

activerecord/test/cases/reflection_test.rb

@@ -254,23 +254,34 @@ def test_chain
   end
 
   def test_scope_chain_does_not_interfere_with_hmt_with_polymorphic_case
-    @hotel = Hotel.create!
-    @department = @hotel.departments.create!
-    @department.chefs.create!(employable: CakeDesigner.create!)
-    @department.chefs.create!(employable: DrinkDesigner.create!)
+    hotel = Hotel.create!
+    department = hotel.departments.create!
+    department.chefs.create!(employable: CakeDesigner.create!)
+    department.chefs.create!(employable: DrinkDesigner.create!)
 
-    assert_equal 1, @hotel.cake_designers.size
-    assert_equal 1, @hotel.drink_designers.size
-    assert_equal 2, @hotel.chefs.size
+    assert_equal 1, hotel.cake_designers.size
+    assert_equal 1, hotel.cake_designers.count
+    assert_equal 1, hotel.drink_designers.size
+    assert_equal 1, hotel.drink_designers.count
+    assert_equal 2, hotel.chefs.size
+    assert_equal 2, hotel.chefs.count
   end
 
   def test_scope_chain_does_not_interfere_with_hmt_with_polymorphic_case_and_sti
-    @hotel = Hotel.create!
-    @hotel.mocktail_designers << MocktailDesigner.create!
+    hotel = Hotel.create!
+    hotel.mocktail_designers << MocktailDesigner.create!
+
+    assert_equal 1, hotel.mocktail_designers.size
+    assert_equal 1, hotel.mocktail_designers.count
+    assert_equal 1, hotel.chef_lists.size
+    assert_equal 1, hotel.chef_lists.count
+
+    hotel.mocktail_designers = []
 
-    assert_equal 1, @hotel.mocktail_designers.size
-    assert_equal 1, @hotel.mocktail_designers.count
-    assert_equal 1, @hotel.chef_lists.size
+    assert_equal 0, hotel.mocktail_designers.size
+    assert_equal 0, hotel.mocktail_designers.count
+    assert_equal 0, hotel.chef_lists.size
+    assert_equal 0, hotel.chef_lists.count
   end
 
   def test_scope_chain_of_polymorphic_association_does_not_leak_into_other_hmt_associations