[wp-trac] [WordPress Trac] #33972: static use of PHPMailer class results in stale state between calls to wp_mail()

[WordPress Trac]

#33972: static use of PHPMailer class results in stale state between calls to
wp_mail()
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 Reporter:  codebuddy                            |       Owner:  rishabhwp
     Type:  defect (bug)                         |      Status:  assigned
 Priority:  normal                               |   Milestone:  Future
                                                 |  Release
Component:  Mail                                 |     Version:  4.3
 Severity:  critical                             |  Resolution:
 Keywords:  has-test-info good-first-bug has-    |     Focuses:
  patch needs-testing has-unit-tests has-dev-    |
  note                                           |
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Changes (by dilip2615):

 * keywords:  has-test-info good-first-bug has-patch needs-testing =>
     has-test-info good-first-bug has-patch needs-testing has-unit-tests
     has-dev-note


Comment:

 == Test Report
 === Description
 This report validates that the fix for #33972 works as expected on the
 current trunk.

 Patch tested: trunk @ becfe55789

 === Environment
 - WordPress: 6.8.2
 - PHP: 8.2.23
 - Server: nginx/1.26.1
 - Database: mysqli (Server: 8.0.35 / Client: mysqlnd 8.2.23)
 - Browser: Chrome 140.0.0.0
 - OS: Windows 10/11
 - Theme: Twenty Twenty-One 2.5
 - MU Plugins: None activated
 - Plugins:
   * Test Reports 1.2.0

 === Steps to Reproduce (Before)
 1. On trunk, executed unit tests for wp_mail:
    `npm run test:php -- tests/phpunit/tests/pluggable/wpMail.php`
 2. Optional manual: Sent two consecutive `wp_mail()` calls (first forces
 base64, second default) and inspected PHPMailer `Encoding` via
 `phpmailer_init`.

 === Actual Results (After)
 1. ✅ Unit tests: `OK (27 tests, 66 assertions)`
 2. ✅ No Encoding bleed between consecutive `wp_mail()` calls;
 headers/content behave as expected.

 === Additional Notes
 - Could not reproduce the issue on the current trunk; behavior appears
 correct.
 - ✅ Tested on trunk @ becfe55789
      Unit tests: OK (27 tests, 66 assertions)
      Observation: Encoding bleed not reproducible on trunk.

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Ticket URL: <https://core.trac.wordpress.org/ticket/33972#comment:31>
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