README

Fixes affiliate attribution loss in Amasty Affiliate when a non-affiliate coupon code is applied alongside an affiliate cookie.

The Problem

When a customer arrives via an affiliate link, Amasty Affiliate sets a cookie (current_affiliate_account_code). During cart calculation, AffiliateQuoteResolver::resolveAffiliateAccount() uses this cookie to identify the affiliate.

However, the method uses a priority chain with a bug:

1. Check quote->getCouponCode() — if found, look it up in the affiliate coupon table
2. If the coupon is not an affiliate coupon → NoSuchEntityException → return null immediately
3. Only if no coupon code is present → read the cookie

When a customer enters a regular (non-affiliate) coupon, step 2 short-circuits and the affiliate cookie is never checked. This causes:

• Affiliate rules are no longer applied during cart calculation
• SalesOrderAfterPlaceObserver cannot find an affiliate account → no transaction → attribution lost

The Fix

1. Cookie Fallback (AffiliateQuoteResolverPlugin)

An after plugin on AffiliateQuoteResolver::resolveAffiliateAccount() that falls back to the cookie when the original method returns null but the cookie is present.

2. Max-of-Two Discount (DiscountMaxComparisonPlugin)

An after plugin on Magento\SalesRule\Model\Quote\Discount::collect() that prevents affiliate and coupon discounts from stacking. When both apply to the same item, only the larger discount is kept.

• Coupon-specific rules (requiring a coupon code) are compared against affiliate rules
• Non-coupon rules (auto/site-wide sales) are not affected — they always apply
• Per-item comparison using Magento's built-in per-rule discount breakdown

Installation

composer require pixelperfectat/magento2-module-amasty-affiliate-attribution-fix
bin/magento module:enable PixelPerfect_AmastyAffiliateAttributionFix
bin/magento setup:upgrade

Configuration

None required — the module works automatically once installed.

Discount Stacking Behaviour

To control stacking per-rule via Magento's built-in mechanism, set stop_rules_processing on individual sales rules.

Compatibility

• PHP 8.3+
• Magento 2.4.x
• Amasty Affiliate 2.3.0+

Testing

vendor/bin/phpunit

Manual Verification

1. Click an affiliate link → verify cookie is set
2. Add items to cart
3. Apply a regular (non-affiliate) coupon code
4. Place order
5. Check amasty_affiliate_transaction table → affiliate transaction exists
6. Check Admin → Affiliate → Transactions → order appears with correct affiliate