Fix checkout fatal when a cart line price is not numeric

[ismaeldcom]

Description

• Guard the cart line item build in get_line_items() with is_numeric( $unit_price ), so a malformed price never reaches the totals arithmetic.

wc_format_decimal( $product->get_price() ) reduces a malformed price to '' or '-', and calculate_totals() multiplies that by the quantity, which is a TypeError on PHP 8 that takes the whole checkout page down. The way in is a pricing plugin filtering woocommerce_product_get_price after the item is already in the cart, since WooCommerce will not let you add a product with no price.

is_numeric() rather than a truthiness check because '-' is truthy and would still fatal, and '0' is falsy and must not be dropped, see test_zero_amount_response_persists_real_itemized_rates() for what the response to a $0 line carries.

The skipped line gets no tax row. Nothing is lost by that, on trunk it got none either because the page died and took the rest of the cart's tax with it.

Related issue(s)

Closes WOOTAX-339

Steps to reproduce & screenshots/GIFs

• Check out trunk and enable automated taxes.
• Set the store address to a US one, for example 1 Main St, Denver, CO 80202.
• Log in as a customer whose billing and shipping address is the same state, with a postcode and city filled in. Without them the tax call aborts and nothing happens.
• Add this to a mu-plugin. Filtering globally instead would make the product unpurchasable and WooCommerce would drop it from the cart.

add_action( 'woocommerce_after_calculate_totals', function () {
	add_filter( 'woocommerce_product_get_price', function () { return '-'; }, 99, 0 );
}, 19 );
add_action( 'woocommerce_after_calculate_totals', function () {
	remove_all_filters( 'woocommerce_product_get_price', 99 );
}, 21 );

• Add a product to the cart and open the checkout page.
• The page should show Uncaught TypeError: Unsupported operand types: string * int in class-wc-connect-taxjar-integration.php:614.
• Check out this PR branch and reload the checkout.
• The page should render, with its tax rows in the order table.

A zero price must still be sent

• Enable debug_logging_enabled so the WCS Tax log records Requesting: taxjar/v2/taxes.
• Remove the mu-plugin, then put a normally priced product and a product priced 0 in the cart.
• Open the checkout on trunk and on this branch.
• The logged request should carry "unit_price":"0" on both, and the order totals should be identical.

Checklist

• unit tests
• changelog.txt entry added
• readme.txt entry added

[Copilot]

Pull request overview

Prevents a PHP 8 checkout fatal in the TaxJar integration when a pricing extension (or other customization) makes a cart line’s unit price non-numeric after the item is already in the cart, by guarding get_line_items().

Changes:

• Skip building TaxJar line items when unit_price is non-numeric (while still allowing 0).
• Add unit tests covering non-numeric prices being skipped and zero prices being preserved.
• Add changelog/readme entries for the fix.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
classes/class-wc-connect-taxjar-integration.php	Adds an is_numeric( $unit_price ) guard when building checkout line items to avoid PHP 8 arithmetic TypeErrors.
tests/php/test-class-wc-connect-taxjar-integration.php	Adds tests for skipping non-numeric prices and preserving $0 line items; extends teardown cleanup for the price filter.
changelog.txt	Documents the checkout fatal fix in the plugin changelog.
readme.txt	Documents the checkout fatal fix in the readme changelog section.

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