Fix PDF Credit Note Generation Crash by WC_Order check

[faisal-alvi]

All Submissions:

• Does your code follow the WooCommerce Sniffs variant of WordPress coding standards?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?
• Will this change require new documentation or changes to existing documentation?

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Changes proposed in this Pull Request:

This PR fixes a critical issue where the Square plugin's filter_order_item_totals function causes fatal errors when generating PDF credit notes with third-party PDF invoice plugins.

The filter_order_item_totals function assumes the $order parameter is always a WC_Order object and calls $order->get_payment_method() without validation. However, when generating credit notes, PDF plugins pass a WC_Order_Refund object, which doesn't have the get_payment_method() method, causing a fatal error.

Closes https://linear.app/a8c/issue/SQUARE-180/square-plugin-crashes-pdf-credit-note-generation-for-3pd-plugin.

Steps to test the changes in this Pull Request:

I wasn’t able to reproduce the issue myself, but the fix is straightforward and non-harmful. Here are the steps that may help reproduce the issue and confirm the fix.

1. Setup Test Environment:

   • Active WooCommerce Square plugin
   • Install a third-party PDF plugin (e.g., PDF Invoices & Packing Slips for WooCommerce)
   • Create a test order with Square payment method

2. Test Regular PDF Generation:

   • Generate a PDF invoice for the test order
   • Verify the PDF generates successfully

Changelog entry

Fix - Prevent fatal error when generating PDF credit notes with third-party PDF plugins by adding type check for WC_Order objects in filter_order_item_totals function.

[qasumitbagthariya]

QA Update - Need Feedback ⚠️

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Hello @dkotter

I tested this from my end and I’m not able to reproduce the issue.

PDF Invoices & Packing Slips for WooCommerce

Screen.Recording.2025-10-03.at.11.37.25.PM.mov

Testing Environment

• WordPress: 6.8.3
• Theme: Twenty Twenty-Five 1.3
• WooCommerce - 10.2.2
• PDF Invoices & Packing Slips for WooCommerce - 4.7.0
• PHP: 8.0.30
• Web Server: Nginx 1.20.2
• Browser: Chrome
• OS: macOS 15.2
• Branch: trunk

[dkotter]

I tested this from my end and I’m not able to reproduce the issue.

Looks like Faisal also wasn't able to reproduce this. Looking at the code change, I don't have any concern with us shipping this though also fine to close this out if we think that's best; cc: @jeffpaul @vikrampm1