feature #50911 [HttpKernel] Enhance exception if possible (lyrixx)

This PR was merged into the 6.4 branch.

Discussion
----------

[HttpKernel] Enhance exception if possible

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | no
| New feature?  | restore an old feature
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        |

I don't know if it's the best place to do that.
I think in the kernel, it would be better, WDYT?

Before

![image](https://github.com/symfony/symfony/assets/408368/e2a452aa-b669-4598-8b23-5366c5b80a74)

After :

![image](https://github.com/symfony/symfony/assets/408368/0e30c50d-5c94-43db-a9e5-19be6ccd5f2b)

Commits
-------

2bfb9d9128 [HttpKernel] Enhance exception if possible

Author: fabpot

ErrorHandler.php

@@ -517,14 +517,7 @@ public function handleException(\Throwable $exception): void
             }
         }
 
-        if (!$exception instanceof OutOfMemoryError) {
-            foreach ($this->getErrorEnhancers() as $errorEnhancer) {
-                if ($e = $errorEnhancer->enhance($exception)) {
-                    $exception = $e;
-                    break;
-                }
-            }
-        }
+        $exception = $this->enhanceError($exception);
 
         $exceptionHandler = $this->exceptionHandler;
         $this->exceptionHandler = [$this, 'renderException'];
@@ -662,6 +655,21 @@ private function renderException(\Throwable $exception): void
         echo $exception->getAsString();
     }
 
+    public function enhanceError(\Throwable $exception): \Throwable
+    {
+        if ($exception instanceof OutOfMemoryError) {
+            return $exception;
+        }
+
+        foreach ($this->getErrorEnhancers() as $errorEnhancer) {
+            if ($e = $errorEnhancer->enhance($exception)) {
+                return $e;
+            }
+        }
+
+        return $exception;
+    }
+
     /**
      * Override this method if you want to define more error enhancers.
      *

Tests/ErrorHandlerTest.php

@@ -363,13 +363,14 @@ public function testHandleDeprecation()
     /**
      * @dataProvider handleExceptionProvider
      */
-    public function testHandleException(string $expectedMessage, \Throwable $exception)
+    public function testHandleException(string $expectedMessage, \Throwable $exception, string $enhancedMessage = null)
     {
         try {
             $logger = $this->createMock(LoggerInterface::class);
             $handler = ErrorHandler::register();
 
             $logArgCheck = function ($level, $message, $context) use ($expectedMessage, $exception) {
+                $this->assertSame('critical', $level);
                 $this->assertSame($expectedMessage, $message);
                 $this->assertArrayHasKey('exception', $context);
                 $this->assertInstanceOf($exception::class, $context['exception']);
@@ -388,11 +389,13 @@ public function testHandleException(string $expectedMessage, \Throwable $excepti
                 $handler->handleException($exception);
                 $this->fail('Exception expected');
             } catch (\Throwable $e) {
-                $this->assertSame($exception, $e);
+                $this->assertInstanceOf($exception::class, $e);
+                $this->assertSame($enhancedMessage ?? $exception->getMessage(), $e->getMessage());
             }
 
-            $handler->setExceptionHandler(function ($e) use ($exception) {
-                $this->assertSame($exception, $e);
+            $handler->setExceptionHandler(function ($e) use ($exception, $enhancedMessage) {
+                $this->assertInstanceOf($exception::class, $e);
+                $this->assertSame($enhancedMessage ?? $exception->getMessage(), $e->getMessage());
             });
 
             $handler->handleException($exception);
@@ -412,6 +415,11 @@ public static function handleExceptionProvider(): array
             })::class.' bar')],
             ['Uncaught Error: bar', new \Error('bar')],
             ['Uncaught ccc', new \ErrorException('ccc')],
+            [
+                'Uncaught Error: Class "App\Controller\ClassDoesNotExist" not found',
+                new \Error('Class "App\Controller\ClassDoesNotExist" not found'),
+                "Attempted to load class \"ClassDoesNotExist\" from namespace \"App\Controller\".\nDid you forget a \"use\" statement for another namespace?",
+            ],
         ];
     }