Properly handle multibyte characters in postcode templates for tax calculation

[sambolek]

Preconditions and environment

• Magento 2.4.8-p3

Steps to reproduce

1. Add product to cart
2. Go to checkout as guest
3. Enter "31000 Šibenik" as postcode

Expected result

There are available shipping methods and you can proceed to the next step.

Actual result

1. Observe that "estimate-shipping-methods" ajax call returns errors 500 with message "Unable to serialize value. Error: Malformed UTF-8 characters, possibly incorrectly encoded"
2. Check logs and observe that there is a MySQL DB error

SQLSTATE[HY000]: General error: 1271 Illegal mix of collations for operation 'in', query was: SELECT `main_table`.`tax_calculation_rate_id`, `main_table`.`tax_calculation_rule_id`, `main_table`.`customer_tax_class_id`, `main_table`.`product_tax_class_id`, `rule`.`priority`, `rule`.`position`, `rule`.`calculate_subtotal`, `rate`.`rate` AS `value`, `rate`.`tax_country_id`, `rate`.`tax_region_id`, `rate`.`tax_postcode`, `rate`.`tax_calculation_rate_id`, `rate`.`code`, IF(title_table.value IS NULL, rate.code, title_table.value) AS `title` FROM `tax_calculation` AS `main_table`
 INNER JOIN `tax_calculation_rule` AS `rule` ON `rule`.`tax_calculation_rule_id` = main_table.tax_calculation_rule_id
 INNER JOIN `tax_calculation_rate` AS `rate` ON rate.tax_calculation_rate_id = main_table.tax_calculation_rate_id
 LEFT JOIN `tax_calculation_rate_title` AS `title_table` ON rate.tax_calculation_rate_id = title_table.tax_calculation_rate_id AND title_table.store_id = '1' WHERE (customer_tax_class_id = 10) AND (product_tax_class_id IN ('11')) AND (rate.tax_country_id = 'HR') AND (rate.tax_region_id IN(0, 0)) AND (rate.zip_is_range IS NULL) AND (rate.tax_postcode IS NULL OR rate.tax_postcode IN('*', '', '31000 šib', '31000 šib*', '31000 ši*', '31000 š*', '31000 �*', '31000 *', '31000*', '3100*', '310*', '31*', '3*')) ORDER BY `priority` ASC, `tax_calculation_rule_id` ASC, `tax_country_id` DESC, `tax_region_id` DESC, `tax_postcode` DESC, `value` DESC

Additional information

The issue comes from using "strlen" and "substr" in fields which do not handle multibyte characters properly.

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 @sambolek. Thank you for your report.
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[m2-assistant]

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[hostep]

This sounds like a duplicate of #40138 which already has a pending fix: #40142