feature symfony#51926 [Mime] Forbid messages that are generators to be used more than once (fabpot)

This PR was merged into the 6.4 branch.

Discussion
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[Mime] Forbid messages that are generators to be used more than once

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | yes
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | Fix symfony#51764, Fix symfony#51874
| License       | MIT

This is a continuation of symfony#51874, when someone tries to send the same message more than once.
`@chalasr` `@stof`

Commits
-------

3c5fe51 [Mime] Forbid messages that are generators to be used more than once

Author: fabpot

src/Symfony/Component/Mime/RawMessage.php

@@ -19,6 +19,7 @@
 class RawMessage
 {
     private iterable|string|null $message = null;
+    private bool $isGeneratorClosed;
 
     public function __construct(iterable|string $message)
     {
@@ -41,12 +42,29 @@ public function toString(): string
 
     public function toIterable(): iterable
     {
+        if ($this->isGeneratorClosed ?? false) {
+            trigger_deprecation('symfony/mime', '6.4', 'Sending an email with a closed generator is deprecated and will throw in 7.0.');
+            // throw new LogicException('Unable to send the email as its generator is already closed.');
+        }
+
         if (\is_string($this->message)) {
             yield $this->message;
 
             return;
         }
 
+        if ($this->message instanceof \Generator) {
+            $message = '';
+            foreach ($this->message as $chunk) {
+                $message .= $chunk;
+                yield $chunk;
+            }
+            $this->isGeneratorClosed = !$this->message->valid();
+            $this->message = $message;
+
+            return;
+        }
+
         foreach ($this->message as $chunk) {
             yield $chunk;
         }

src/Symfony/Component/Mime/Tests/RawMessageTest.php

@@ -12,10 +12,13 @@
 namespace Symfony\Component\Mime\Tests;
 
 use PHPUnit\Framework\TestCase;
+use Symfony\Bridge\PhpUnit\ExpectDeprecationTrait;
 use Symfony\Component\Mime\RawMessage;
 
 class RawMessageTest extends TestCase
 {
+    use ExpectDeprecationTrait;
+
     /**
      * @dataProvider provideMessages
      */
@@ -46,6 +49,37 @@ public function testSerialization(mixed $messageParameter, bool $supportReuse)
         }
     }
 
+    /**
+     * @dataProvider provideMessages
+     */
+    public function testToIterable(mixed $messageParameter, bool $supportReuse)
+    {
+        $message = new RawMessage($messageParameter);
+        $this->assertEquals('some string', implode('', iterator_to_array($message->toIterable())));
+
+        if ($supportReuse) {
+            // calling methods more than once work
+            $this->assertEquals('some string', implode('', iterator_to_array($message->toIterable())));
+        }
+    }
+
+    /**
+     * @dataProvider provideMessages
+     *
+     * @group legacy
+     */
+    public function testToIterableLegacy(mixed $messageParameter, bool $supportReuse)
+    {
+        $message = new RawMessage($messageParameter);
+        $this->assertEquals('some string', implode('', iterator_to_array($message->toIterable())));
+
+        if (!$supportReuse) {
+            // in 7.0, the test with a generator will throw an exception
+            $this->expectDeprecation('Since symfony/mime 6.4: Sending an email with a closed generator is deprecated and will throw in 7.0.');
+            $this->assertEquals('some string', implode('', iterator_to_array($message->toIterable())));
+        }
+    }
+
     public static function provideMessages(): array
     {
         return [