Deprecated wp-includes/SMTP.php should use require_once to include the new namespaced class

[greatsaltlake]

Currently the deprecated file uses

<?php
require __DIR__ . '/PHPMailer/SMTP.php';

which can lead to a fatal error if that class or the deprecated file has already been loaded.

[audrasjb]

Hi @greatsaltlake, welcome to WordPress Core Trac and thank you for opening this ticket.

The bug report makes sense to me.

Moving it to the current milestone (5.7) and adding the good-first-bug workflow keyword as this is a good ticket to onboard people for their very first contribution.

I'm unsure about moving this to External libraries component, though. @SergeyBiryukov as WP 5.7 Core Tech Lead, I’d rely on you for moving this to the best component if needed :)

[SergeyBiryukov]

Good catch, introduced in [48033] / #41750.

This was solved for wp-includes/class-phpmailer.php in [48530] / #50716, but not for class-smtp.php.

Since wp-includes/class-smtp.php is no longer an external file, moving to the Mail component.

[oellin]

Hi,

This is my first contribution.

In this patch i replaced require with require_once.

[SergeyBiryukov]

Replying to oellin:

This is my first contribution.

The patch looks great, thank you :)

[SergeyBiryukov]

In 50022:

Mail: Make sure the SMTP class is only required once if a plugin requires wp-includes/class-smtp.php directly.

Follow-up to [48033], [48530].

Props oellin, greatsaltlake, audrasjb.
Fixes #52369. See #50716, #41750.