minor #21407 [WebServerBundle] Improved exception message (wouterj)

This PR was merged into the 3.3-dev branch.

Discussion
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[WebServerBundle] Improved exception message

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

This is a quite minor one, but imo "guessing" is something that's optional. If I don't pass value X, a script will guess value X. However, in this case, the front controller file cannot be specified. It has to be one of the "guessed" file names. That's why I renamed "guessing" to "finding".

While doing this, I also added the possible file names in the exception message to ease fixing problems.

Commits
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df46188 Improved exception message

src/Symfony/Bundle/WebServerBundle/WebServerConfig.php

@@ -28,8 +28,8 @@ public function __construct($documentRoot, $env, $address = null, $router = null
             throw new \InvalidArgumentException(sprintf('The document root directory "%s" does not exist.', $documentRoot));
         }
 
-        if (null === $file = $this->guessFrontController($documentRoot, $env)) {
-            throw new \InvalidArgumentException(sprintf('Unable to guess the front controller under "%s".', $documentRoot));
+        if (null === $file = $this->findFrontController($documentRoot, $env)) {
+            throw new \InvalidArgumentException(sprintf('Unable to find the front controller under "%s" (none of these files exist: %s).', $documentRoot, implode(', ', $this->getFrontControllerFileNames($env))));
         }
 
         putenv('APP_FRONT_CONTROLLER='.$file);
@@ -87,21 +87,22 @@ public function getAddress()
         return $this->hostname.':'.$this->port;
     }
 
-    private function guessFrontController($documentRoot, $env)
+    private function findFrontController($documentRoot, $env)
     {
-        foreach (array('app', 'index') as $prefix) {
-            $file = sprintf('%s_%s.php', $prefix, $env);
-            if (file_exists($documentRoot.'/'.$file)) {
-                return $file;
-            }
+        $fileNames = $this->getFrontControllerFileNames($env);
 
-            $file = sprintf('%s.php', $prefix);
-            if (file_exists($documentRoot.'/'.$file)) {
-                return $file;
+        foreach ($fileNames as $fileName) {
+            if (file_exists($documentRoot.'/'.$fileName)) {
+                return $fileName;
             }
         }
     }
 
+    private function getFrontControllerFileNames($env)
+    {
+        return array('app_'.$env.'.php', 'app.php', 'index_'.$env.'.php', 'index.php');
+    }
+
     private function findBestPort()
     {
         $port = 8000;