Problem Statement

Context

Merchant reported issues with shipping_method parameter being sent incorrectly to Amazon, causing wrong shipping methods to appear on Amazon Seller Central (e.g., "Standard", "SecondDay" instead of the configured "ECONOMY").

Related Ticket: PCMT-1474
Account ID: 17025 (MAGNETRON S.A)
Marketplace: Amazon ES
Plugin Version: 3.9.4
PrestaShop Version: 1.7.8.8

Issues to Fix

1. Shipping method sent even when optional

• Amazon API defines shipping_method as optional with accept_free_values: true
• Current code sends default values ("Standard", "SecondDay") from the original Amazon order import
• These values don't match merchant's Amazon Seller configuration (wants "ECONOMY")

2. No free text input field

• Amazon accepts free text values for shipping_method
• Plugin only shows dropdown with fixed values from API
• Merchant cannot enter custom values like "ECONOMY" that exist in their Seller Central

3. Dropdown shows pre-selected value when nothing is saved

• UI shows "NextDay" selected by default even when database value is NULL
• Confusing for merchant who thinks a value is selected when it's not
• Should show empty/blank option by default

4. "null" values appear in dropdown

• Some shipping methods from API have lengow_code: null
• Example: "Priority": {"label": "Priority", "lengow_code": null}
• These "null" values pollute the dropdown list

Expected Behavior

1. ✅ Only send shipping_method when:

   • It's a required parameter for the marketplace, OR
   • It's optional AND has a non-empty value

2. ✅ Allow free text input:

   • Add text input field alongside dropdown
   • Merchant can type any value (e.g., "ECONOMY", "EXPRESS")
   • Text input takes priority over dropdown selection

3. ✅ Empty by default:

   • Show "-- No shipping method selected --" option
   • Pre-select empty option when no value in database
   • No confusion about whether a value is selected

4. ✅ Filter null values:

   • Remove shipping methods with lengow_code: null from dropdown
   • Clean display of available options

Files to Modify

Backend Changes

1. classes/models/LengowMarketplace.php (line 507-509)
   • Modify getAllParams() method
   • Check if shipping_method is required vs optional
   • Only send if required OR (optional AND not empty)

case LengowAction::ARG_SHIPPING_METHOD:
    // Determine if shipping_method is required or optional for this marketplace
    $isRequired = isset($actions['args']) && in_array(LengowAction::ARG_SHIPPING_METHOD, $actions['args'], true);
    
    if ($isRequired) {
        // Required parameter: always send (even if empty)
        $params[$arg] = $shippingMethod ?? '';
    } else {
        // Optional parameter: only send if not empty
        // This avoids sending Amazon default values like "Standard", "SecondDay"
        if (!empty($shippingMethod)) {
            $params[$arg] = $shippingMethod;
        }
    }
    break;

2. classes/models/LengowHook.php or controller preparing template data
   • Filter out shipping methods with null lengow_code
   • Before passing to template, filter array:

$shippingMethods = array_filter($shippingMethods, function($method) {
    return !empty($method['method_lengow_code']) 
        && $method['method_lengow_code'] !== 'null' 
        && $method['method_lengow_code'] !== 'NULL';
});

3. classes/controllers/LengowOrderController.php (save_shipping_method action)
   • Accept free text values (not just dropdown values)
   • Allow empty/null values to be saved

Frontend Changes

4. views/templates/hook/order/admin_order_side.tpl
   • Add "-- No shipping method selected --" as first option
   • Add free text input field below dropdown
   • Add help text explaining Amazon accepts free values
   • Sync dropdown and text field with JavaScript
   • Filter out null values in Smarty loop
   • Update save button to use text field value if filled, otherwise dropdown

Acceptance Criteria

• When shipping_method is optional (like Amazon), it's NOT sent if empty
• When shipping_method is required (other marketplaces), it's always sent
• Merchant can type custom shipping method value (free text)
• Dropdown shows "-- No shipping method selected --" when no value saved
• No "null" values appear in dropdown list
• Text input field takes priority over dropdown when both have values
• Saving works correctly for both dropdown selections and custom text
• Existing functionality for other marketplaces remains unchanged

Test Cases

1. Test Amazon order with no shipping_method set:

   • Create/import Amazon order
   • Don't set shipping_method
   • Trigger ship action
   • Verify shipping_method parameter is NOT sent to Lengow API

2. Test Amazon order with custom shipping_method:

   • Set custom value "ECONOMY" via text field
   • Save
   • Trigger ship ac...