How to Migrate Shipping Script for PO Box & Return Logic to Shopify Functions?

[xlogicsolutionsgn]

Hi Shopify Community,

I’m currently migrating this custom Shopify Script to a Shopify Function as well, since Shopify Scripts are being deprecated. This script controls which shipping rates are displayed to customers based on specific conditions.

1. Whether the shipping address is a PO Box
2. Whether the order is a return/exchange (based on line item properties)

This script is essential to our shipping experience, and I’d like to help replicate this logic using Shopify Functions (likely through a Delivery Customisation Function).

What the Script Does:

1. PO Box Address Handling

• If the shipping address contains PO Box-related terms (e.g. “P.O. Box”, “Postal Box”), only specific shipping rates (e.g. USPS) are shown.
• All other shipping rates are hidden.

2. Return Shipping Logic

• If none of the cart items include a custom property like exchange_credit, the script removes any shipping rates labeled “return shipping”.

What I Need Help With:

I want to recreate the exact logic in Shopify Functions, but I’m not sure how to:

• Check if address1 or address2 contains PO Box triggers in a Delivery Customization Function
• Show/hide shipping rates based on string matching (partial or exact) of the rate name
• Detect line item properties (e.g. exchange_credit) in the input and use them to filter rates
• Implement the conditional logic that only shows USPS if PO Box is found

# ================= Customizable Settings =================
SHOW_RATES_FOR_ZIP_PROVINCE_COUNTRY = [
  {
    po_box_triggers: [
      "po box", "post office", "p o box", "p.o.box", "p.o. box", "p.o box", "pobox",
      "post office box", "post box", "p. o. box", "po. box", "postal box", "postal code", "PO Box",
    ],
    rate_match_type: :exact,
    rate_names: ["USPS *(ONLY OPTION FOR P.O. BOX/APO/FPO/DPO)"],
  },
]

# ========== Helper Classes ==========

class RateNameSelector
  def initialize(match_type, rate_names)
    @match_type = match_type
    @comparator = match_type == :exact ? '==' : 'include?'
    @rate_names = rate_names&.map { |rate_name| rate_name.downcase.strip }
  end

  def match?(shipping_rate)
    if @match_type == :all
      true
    else
      @rate_names.any? { |name| shipping_rate.name.downcase.send(@comparator, name) }
    end
  end
end

class AddressSelector
  def initialize(triggers)
    @triggers = triggers.map { |trigger| trigger.downcase.strip }
  end

  def match?(address)
    address_fields = [address.address1, address.address2].map do |line|
      line.nil? ? "" : line.downcase
    end

    address_fields = address_fields.join(" ")
    @triggers.any? { |trigger| address_fields.include?(trigger) }
  end
end

class ShowRatesForZipProvinceCountryCampaign
  def initialize(campaigns)
    @campaigns = campaigns
  end

  def run(cart, shipping_rates)
    address = cart.shipping_address

    @campaigns.each do |campaign|
      rate_name_selector = RateNameSelector.new(campaign[:rate_match_type], campaign[:rate_names])

      if address.nil?
        full_match = false
      else
        country_match = AddressSelector.new(campaign[:po_box_triggers]).match?(address)
        full_match = country_match
      end

      shipping_rates.delete_if do |shipping_rate|
        rate_name_selector.match?(shipping_rate) != full_match
      end
    end
  end
end

# ========== Run Campaigns ==========
CAMPAIGNS = [
  ShowRatesForZipProvinceCountryCampaign.new(SHOW_RATES_FOR_ZIP_PROVINCE_COUNTRY),
]

CAMPAIGNS.each do |campaign|
  campaign.run(Input.cart, Input.shipping_rates)
end

# ========== Narvar Return Shipping Filter ==========
is_return = Input.cart.line_items.map { |x|
  x.properties.keys.include?('exchange_credit') || x.properties.keys.include?('_exchange_credit') ||
    x.properties.keys.include?('narvar_exchange_credit') || x.properties.keys.include?('_narvar_exchange_credit')
}.any?

if !is_return
  Input.shipping_rates.delete_if do |shipping_rate|
    shipping_rate.name.downcase.include?('return shipping')
  end
end

# ========== Output ==========
Output.shipping_rates = Input.shipping_rates

Would Appreciate Guidance On:

• Mapping these classes and matchers into JavaScript (Wasm) or Rust as a Shopify Function
• Best practices for rate filtering and property checking in the new framework
• Any sample templates or community examples doing similar filtering logic

---

Thanks in advance for your help! I’d be happy to share a working Function example once it’s built, in case it helps others too.

[SealSubs-Roan]

Shopify Delivery Customization Function if the PO Box can be detected using regex on the address field used in rate filtering. Use a custom cart attribute or line item property for Return logic to pass in, based on that filter rates. For additional flexibility, you may also use Shopify’s Functions API with an edge function.