Merge branch '5.1'

* 5.1:
  Update UPGRADE-5.1.md
  [HttpKernel] Adjust tests to new "class not found" error message format.
  Don't call createMock with an array of interfaces.
  [FrameworkBundle] Fix Tests on PHPUnit 9.3.
  [WebProfilerBundle] Fix Tests on PHPUnit 9.3.
  esmtp error not being thrown properly
  [Yaml Parser] fixed Parser to skip comments when inlining sequences
  Update Connection.php
  [DI] fix generating preload file when cache_dir is outside project_dir
  Fix CacheCollectorPass with decorated cache pools
  [PhpUnitBridge] CoverageListenerTrait update for PHPUnit 8.5/9.x
  Remove invalid instantiation declaration
  [PropertyInfo] Fix typed collections in PHP 7.4

Author: fabpot

Dumper/PhpDumper.php

@@ -326,7 +326,7 @@ class %s extends {$options['class']}
             $this->asFiles = false;
 
             if ($this->preload && null !== $autoloadFile = $this->getAutoloadFile()) {
-                $autoloadFile = substr($this->export($autoloadFile), 2, -1);
+                $autoloadFile = trim($this->export($autoloadFile), '()\\');
 
                 $preloadedFiles = array_reverse($preloadedFiles);
                 $preloadedFiles = implode("';\nrequire __DIR__.'/", $preloadedFiles);
@@ -2123,9 +2123,7 @@ private function doExport($value, bool $resolveEnv = false)
 
     private function getAutoloadFile(): ?string
     {
-        if (null === $this->targetDirRegex) {
-            return null;
-        }
+        $file = null;
 
         foreach (spl_autoload_functions() as $autoloader) {
             if (!\is_array($autoloader)) {
@@ -2144,14 +2142,14 @@ private function getAutoloadFile(): ?string
                 if (0 === strpos($class, 'ComposerAutoloaderInit') && $class::getLoader() === $autoloader[0]) {
                     $file = \dirname((new \ReflectionClass($class))->getFileName(), 2).'/autoload.php';
 
-                    if (preg_match($this->targetDirRegex.'A', $file)) {
+                    if (null !== $this->targetDirRegex && preg_match($this->targetDirRegex.'A', $file)) {
                         return $file;
                     }
                 }
             }
         }
 
-        return null;
+        return $file;
     }
 
     private function getClasses(Definition $definition, string $id): array