Error suppression causes important debug information to be lost

[shachibista]

Q	A
Bug report?	no
Feature request?	no
RFC?	no
How used?	Standalone/Symfony/3party
Swiftmailer version	6.2.1
PHP version	7.1.30

Observed behaviour

Error suppression causes warnings from stream_socket_client to be hidden and errno is 0.

Expected behaviour

Warnings from stream_socket_client should not be hidden by default.

Example

When trying to connect to a mail server with ssl at port 465, with error suppression:

Fatal error: Uncaught Swift_TransportException: Connection could not be established with host mail.example.org [ #0] in /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php:269
Stack trace:
#0 /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php(58): Swift_Transport_StreamBuffer->establishSocketConnection()
#1 /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php(143): Swift_Transport_StreamBuffer->initialize(Array)
#2 /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mailer.php(65): Swift_Transport_AbstractSmtpTransport->start()
#3 /mailtest/test.php(19): Swift_Mailer->send(Object(Swift_Message))
#4 {main}
  thrown in /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php on line 269

Without error suppression:

Warning: stream_socket_client(): Peer certificate CN=`mail.somewhere-else.net' did not match expected CN=`mail.exmaple.org' in /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php on line 267

Warning: stream_socket_client(): Failed to enable crypto in /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php on line 267

Warning: stream_socket_client(): unable to connect to ssl://mail.example.org:465 (Unknown error) in /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php on line 267

Fatal error: Uncaught Swift_TransportException: Connection could not be established with host mail.example.org [ #0] in /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php:269
Stack trace:
#0 /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php(58): Swift_Transport_StreamBuffer->establishSocketConnection()
#1 /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/AbstractSmtpTransport.php(143): Swift_Transport_StreamBuffer->initialize(Array)
#2 /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mailer.php(65): Swift_Transport_AbstractSmtpTransport->start()
#3 /mailtest/test.php(19): Swift_Mailer->send(Object(Swift_Message))
#4 {main}
  thrown in /mailtest/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php on line 269

Error is suppressed at line 267 in StreamBuffer.php:

$this->stream = @stream_socket_client($host.':'.$this->params['port'], $errno, $errstr, $timeout, STREAM_CLIENT_CONNECT, $streamContext);

[fabpot]

Should be fixed by #1202.