[Bug] WooCommerce attachment emails fail on Azure App Service — ABSPATH resolves incorrectly in containerized WordPress (v1.2.1)

[JONeillSr]

Summary

On Azure App Service containerized WordPress deployments, WooCommerce order
notification emails that include attached invoice PDFs fail silently with the
following error in the Azure Email Logs:

Request body validation error. ContentBytes invalid. Should be base64

Basic emails (contact forms, password resets) send successfully. Only emails
with attachments are affected.

---

Root Cause

In admin/mailer/class-azure_app_service_email-controller.php, the
generate_request_body() method resolves attachment paths using ABSPATH:

foreach ($filePaths as $path) {
    if ($path[0] !== '/') {
        $path = ABSPATH . trim($path);
    }
    if (file_exists($path)) { ... }
}

On Azure App Service containerized WordPress, ABSPATH resolves to
/var/www/html while the actual running WordPress root is
/var/www/wordpress. The path resolves incorrectly, file_exists() returns
false, the attachment is silently dropped, and the ACS REST API rejects the
malformed request body.

The "ContentBytes invalid" error is a red herring — the real issue is a path
mismatch between ABSPATH and the actual WordPress root inside the container.

---

Steps to Reproduce

1. Deploy WordPress on Azure App Service (Linux, containerized)
2. Install WooCommerce and the App Service Email plugin v1.2.1
3. Place a test order
4. Observe that the New Order and Processing Order emails never arrive
5. Check Azure Email Logs — error reads "ContentBytes invalid. Should be base64"

---

Expected Behavior

WooCommerce order notification emails send successfully with attached invoice
PDFs via Azure Communication Services.

---

Actual Behavior

Emails with attachments fail. Emails without attachments succeed.

---

Proposed Fix

Replace ABSPATH with a path derived from WP_CONTENT_DIR, which correctly
resolves to the active WordPress root regardless of container layout. Also
adds an empty path guard and immediate trim to prevent related edge case
failures:

foreach ($filePaths as $path) {
    $path = trim($path);
    if (empty($path)) { continue; }
    if ($path[0] !== '/') {
        $wp_root = rtrim(str_replace('wp-content', '', WP_CONTENT_DIR), '/');
        $path = $wp_root . '/' . $path;
    }
    if (file_exists($path)) { ... }
}

A community fix including a PowerShell automation script and full root cause
analysis is documented here:
https://github.com/JONeillSr/Repair-AppServiceEmailAttachmentPatch

---

Environment

Component	Version
App Service Email Plugin	v1.2.1
WordPress	7.x
WooCommerce	8.x+
Azure App Service	Linux, containerized
PHP	8.x

---

Workaround

Apply the patch manually via SSH or using the PowerShell automation script
linked above. The fix is confirmed working in production.