make $context for RecurringMessage::hashedCron() optional

if `$message` is `\Stringable`.

src/Symfony/Component/Scheduler/RecurringMessage.php

@@ -46,8 +46,16 @@ public static function cron(string $expression, object $message): self
         return new self(CronExpressionTrigger::fromSpec($expression), $message);
     }
 
-    public static function hashedCron(string $expression, string $context, object $message): self
+    public static function hashedCron(string $expression, object $message, ?string $context = null): self
     {
+        if (!$context && $message instanceof \Stringable) {
+            $context = (string) $message;
+        }
+
+        if (!$context) {
+            throw new InvalidArgumentException('A context must be provided when the message is not a stringable object.');
+        }
+
         return new self(CronExpressionTrigger::fromHash($expression, $context), $message);
     }
 

src/Symfony/Component/Scheduler/Tests/RecurringMessageTest.php

@@ -0,0 +1,31 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Scheduler\Tests;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Scheduler\RecurringMessage;
+
+class RecurringMessageTest extends TestCase
+{
+    public function testCanCreateHashedCronMessage()
+    {
+        $object = new class() {
+            public function __toString(): string
+            {
+                return 'my task';
+            }
+        };
+
+        $this->assertSame('56 2 * * *', (string) RecurringMessage::hashedCron('#midnight', $object)->getTrigger());
+        $this->assertSame('3 0 * * *', (string) RecurringMessage::hashedCron('#midnight', $object, 'context')->getTrigger());
+    }
+}

src/Symfony/Component/Scheduler/Tests/Trigger/CronExpressionTriggerTest.php

@@ -14,7 +14,7 @@
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Scheduler\Trigger\CronExpressionTrigger;
 
-final class CronExpressionTriggerTest extends TestCase
+class CronExpressionTriggerTest extends TestCase
 {
     /**
      * @dataProvider hashedExpressionProvider
@@ -25,7 +25,7 @@ public function testHashedExpressionParsing(string $input, string $expected)
         $triggerB = CronExpressionTrigger::fromHash($input, 'my task');
         $triggerC = CronExpressionTrigger::fromHash($input, 'another task');
 
-        $this->assertSame('cron: '.$expected, (string) $triggerA);
+        $this->assertSame($expected, (string) $triggerA);
         $this->assertSame((string) $triggerB, (string) $triggerA);
         $this->assertNotSame((string) $triggerC, (string) $triggerA);
     }
@@ -59,7 +59,7 @@ public static function hashedExpressionProvider(): array
 
     public function testFromHashWithStandardExpression()
     {
-        $this->assertSame('cron: 56 20 1 9 0', (string) CronExpressionTrigger::fromHash('56 20 1 9 0', 'some context'));
-        $this->assertSame('cron: 0 0 * * *', (string) CronExpressionTrigger::fromHash('@daily', 'some context'));
+        $this->assertSame('56 20 1 9 0', (string) CronExpressionTrigger::fromHash('56 20 1 9 0', 'some context'));
+        $this->assertSame('0 0 * * *', (string) CronExpressionTrigger::fromHash('@daily', 'some context'));
     }
 }