Add test for collection *_ids= setter when association primary key set

Fixes casting of IDs to the data type of the association primary key,
rather than then the data type of the model's primary key. (Tests use a
string primary key on the association, rather than an int.)

Tests issue #20995

activerecord/CHANGELOG.md

 *   Raise ActiveRecord::RecordNotFound from collection `*_ids` setters
     for unknown IDs with a better error message.
 
+    Changes the collection `*_ids` setters to cast provided IDs the data
+    type of the primary key set in the association, not the model
+    primary key.
+
     *Dominic Cleal*
 
 *   For PostgreSQL >= 9.4 use `pgcrypto`'s `gen_random_uuid()` instead of

activerecord/lib/active_record/associations/collection_association.rb

@@ -68,7 +68,7 @@ def ids_reader
 
       # Implements the ids writer method, e.g. foo.item_ids= for Foo.has_many :items
       def ids_writer(ids)
-        pk_type = reflection.primary_key_type
+        pk_type = reflection.association_primary_key_type
         ids = Array(ids).reject(&:blank?)
         ids.map! { |i| pk_type.cast(i) }
         records = klass.where(reflection.association_primary_key => ids).index_by do |r|

activerecord/lib/active_record/reflection.rb

@@ -397,6 +397,10 @@ def association_primary_key(klass = nil)
         options[:primary_key] || primary_key(klass || self.klass)
       end
 
+      def association_primary_key_type
+        klass.type_for_attribute(association_primary_key)
+      end
+
       def active_record_primary_key
         @active_record_primary_key ||= options[:primary_key] || primary_key(active_record)
       end

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -883,6 +883,13 @@ def test_collection_singular_ids_setter_with_string_primary_keys
 
   end
 
+  def test_collection_singular_ids_setter_with_changed_primary_key
+    company = companies(:first_firm)
+    client = companies(:first_client)
+    company.clients_using_primary_key_ids = [client.name]
+    assert_equal [client], company.clients_using_primary_key
+  end
+
   def test_collection_singular_ids_setter_raises_exception_when_invalid_ids_set
     company = companies(:rails_core)
     ids = [Developer.first.id, -9999]
@@ -890,6 +897,13 @@ def test_collection_singular_ids_setter_raises_exception_when_invalid_ids_set
     assert_match(/Couldn't find all Developers with 'id'/, e.message)
   end
 
+  def test_collection_singular_ids_setter_raises_exception_when_invalid_ids_set_with_changed_primary_key
+    company = companies(:first_firm)
+    ids = [Client.first.name, "unknown client"]
+    e = assert_raises(ActiveRecord::RecordNotFound) { company.clients_using_primary_key_ids = ids }
+    assert_match(/Couldn't find all Clients with 'name'/, e.message)
+  end
+
   def test_build_a_model_from_hm_through_association_with_where_clause
     assert_nothing_raised { books(:awdr).subscribers.where(nick: "marklazz").build }
   end