STDOUT blocks infinitely under Windows when STDERR is filled

TemaYud · web-flow · commit eba33de3e939 · 2023-03-05T22:32:25.000+05:00
stream_get_contents() on STDOUT blocks infinitely under Windows when STDERR is filled under some circumstances.
Open STDERR in append mode ("a"), then this will work.
diff --git a/src/Symfony/Component/Mailer/Transport/Smtp/Stream/ProcessStream.php b/src/Symfony/Component/Mailer/Transport/Smtp/Stream/ProcessStream.php
@@ -35,7 +35,7 @@ public function initialize(): void
         $descriptorSpec = [
             0 => ['pipe', 'r'],
             1 => ['pipe', 'w'],
-            2 => ['pipe', 'w'],
+            2 => ['pipe', 'a'],
         ];
         $pipes = [];
         $this->stream = proc_open($this->command, $descriptorSpec, $pipes);
