Compare lists of other customers get transferred to current customer upon login-as-customer

[bst-biwac]

Preconditions and environment

• Magento version >= 2.4.6
• 1 website
• 2 store groups with 4 store views each

Preconditions

• customer A added products to compare list and has logged out
• customer B added products to compare list and has logged out
• customer C added products to compare list and has not yet logged out
• customer D exists with remote assistance enabled

Steps to reproduce

1. admin > login-as-customer with customer D
2. frontend > log out
3. admin > login-as-customer with customer D

sometimes, step 1. alone suffices for the bug to appear.

Expected result

compare lists for customers A and B stay with customers A and B respectively

Actual result

compare lists of customer A and B get transferred to customer D

Additional information

DB Query debugging results:

1. upon logout, visitor_id for compare items get set to 0.
2. login-as-customer has no visitor ID upon login, so it assumes that all compare items with visitor ID 0 belongs to current customer and updates customer_id in compare item table accordingly

this patch seems to fix it

diff --git a/vendor/magento/module-catalog/Model/ResourceModel/Product/Compare/Item.php b/vendor/magento/module-catalog/Model/ResourceModel/Product/C
index ff29a5a..f05f511 100644
--- a/vendor/magento/module-catalog/Model/ResourceModel/Product/Compare/Item.php
+++ b/vendor/magento/module-catalog/Model/ResourceModel/Product/Compare/Item.php
@@ -152,7 +152,7 @@ class Item extends \Magento\Framework\Model\ResourceModel\Db\AbstractDb
      */
     public function updateCustomerFromVisitor($object)
     {
-        if (!$object->getCustomerId()) {
+        if (!$object->getCustomerId() || !$object->getVisitorId()) {
             return $this;
         }

additionally, sometimes login-as-customer won't work (customer section data error
{"message":"Item (Magento\\Catalog\\Model\\Product\\Interceptor) with the same ID "35910" already exists."}
)
see #40205
#40205

Release note

No response

Triage and priority

• Severity: S0 - Affects critical data or functionality and leaves users without workaround.
• Severity: S1 - Affects critical data or functionality and forces users to employ a workaround.
• Severity: S2 - Affects non-critical data or functionality and forces users to employ a workaround.
• Severity: S3 - Affects non-critical data or functionality and does not force users to employ a workaround.
• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.

[m2-assistant]

Hi @bst-biwac. Thank you for your report.
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[bst-biwac]

DB Query debugging results:

1. upon logout, visitor_id for compare items get set to 0.
2. login-as-customer has no visitor ID upon login, so it assumes, that all compare items with visitor ID 0 belongs to current customer and updates customer_id in compare item table accordingly

[bst-biwac]

reproduced on 2.4.7-p8 too