insert with existing association does not seem to work

[jwoodrow]

Hi 👋

I'm trying to insert multiple new records with a has_many association but it seems like it's not working correctly in this case

class Vehicle < ActiveRecord::Base
  has_many :drivers
end

class Driver < ActiveRecord::Base
  belongs_to :vehicle
end

driver = Driver.create
vehicle = Vehicle.new(drivers: [driver])

Vehicle.import([vehicle], recursive: true, on_duplicate_key_update: :all)
driver.reload.vehicle_id #=> nil

when digging a bit I found that here although models.first.id is set correctly, models.first.association(:drivers).target.first.vehicle.id is nil like its a copy. so since vehicle_id, the foreign key is not set then changed? returns false

Shouldn't this foreign key assignment be done before, so if the only change is the belongs_to association it still detects a change ?

changing

activerecord-import/lib/activerecord-import/import.rb

Lines 977 to 1009 in e3331d5

	def find_associated_objects_for_import(associated_objects_by_class, model)
	associated_objects_by_class[model.class.name] ||= {}
	return associated_objects_by_class unless model.id
	association_reflections =
	model.class.reflect_on_all_associations(:has_one) +
	model.class.reflect_on_all_associations(:has_many)
	association_reflections.each do |association_reflection|
	associated_objects_by_class[model.class.name][association_reflection.name] ||= []
	association = model.association(association_reflection.name)
	association.loaded!
	# Wrap target in an array if not already
	association = Array(association.target)
	changed_objects = association.select { |a| a.new_record? || a.changed? }
	changed_objects.each do |child|
	child.public_send("#{association_reflection.foreign_key}=", model.id)
	# For polymorphic associations
	association_name = if model.class.respond_to?(:polymorphic_name)
	model.class.polymorphic_name
	else
	model.class.base_class
	end
	association_reflection.type.try do |type|
	child.public_send("#{type}=", association_name)
	end
	end
	associated_objects_by_class[model.class.name][association_reflection.name].concat changed_objects
	end
	associated_objects_by_class
	end

like such seems to resolve my issues

def find_associated_objects_for_import(associated_objects_by_class, model)
  associated_objects_by_class[model.class.name] ||= {}
  return associated_objects_by_class unless model.id

  association_reflections =
    model.class.reflect_on_all_associations(:has_one) +
    model.class.reflect_on_all_associations(:has_many)
  association_reflections.each do |association_reflection|
    associated_objects_by_class[model.class.name][association_reflection.name] ||= []

    association = model.association(association_reflection.name)
    association.loaded!

    # Wrap target in an array if not already
    association = Array(association.target)

    # This line is added
    association.each { |child| child.public_send("#{association_reflection.foreign_key}=", model.id) }
    changed_objects = association.select { |a| a.new_record? || a.changed? }
    changed_objects.each do |child|
      # Removed the foreign_key assignment here
      # For polymorphic associations
      association_name = if model.class.respond_to?(:polymorphic_name)
        model.class.polymorphic_name
      else
        model.class.base_class
      end
      association_reflection.type.try do |type|
        child.public_send("#{type}=", association_name)
      end
    end
    associated_objects_by_class[model.class.name][association_reflection.name].concat changed_objects
  end
  associated_objects_by_class
end

Current workaround is also to add driver.send(:mutations_from_database).force_change('vehicle_id') right after assigning the new vehicle to the existing driver. The fact that mutations_from_database is a private method is kind of an indicator that this is not really what it's made for