ensure dump indentation to be greather than zero

src/Symfony/Component/Yaml/Dumper.php

@@ -32,6 +32,10 @@ class Dumper
      */
     public function setIndentation($num)
     {
+        if ($num < 1) {
+            throw new \InvalidArgumentException('The indentation must be greater than zero.');
+        }
+
         $this->indentation = (int) $num;
     }
 

src/Symfony/Component/Yaml/Tests/DumperTest.php

@@ -229,6 +229,24 @@ EOF;
             'paragraph-separator' => array("\t\\P", '"\t\\\\P"'),
         );
     }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     * @expectedExceptionMessage The indentation must be greater than zero
+     */
+    public function testZeroIndentationThrowsException()
+    {
+        $this->dumper->setIndentation(0);
+    }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     * @expectedExceptionMessage The indentation must be greater than zero
+     */
+    public function testNegativeIndentationThrowsException()
+    {
+        $this->dumper->setIndentation(-4);
+    }
 }
 
 class A

src/Symfony/Component/Yaml/Tests/YamlTest.php

@@ -28,4 +28,22 @@ class YamlTest extends \PHPUnit_Framework_TestCase
         $parsedByContents = Yaml::parse($contents);
         $this->assertEquals($parsedByFilename, $parsedByContents);
     }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     * @expectedExceptionMessage The indentation must be greater than zero
+     */
+    public function testZeroIndentationThrowsException()
+    {
+        Yaml::dump(array('lorem' => 'ipsum', 'dolor' => 'sit'), 2, 0);
+    }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     * @expectedExceptionMessage The indentation must be greater than zero
+     */
+    public function testNegativeIndentationThrowsException()
+    {
+        Yaml::dump(array('lorem' => 'ipsum', 'dolor' => 'sit'), 2, -4);
+    }
 }

src/Symfony/Component/Yaml/Yaml.php

@@ -83,6 +83,10 @@ class Yaml
      */
     public static function dump($array, $inline = 2, $indent = 4, $exceptionOnInvalidType = false, $objectSupport = false)
     {
+        if ($indent < 1) {
+            throw new \InvalidArgumentException('The indentation must be greater than zero.');
+        }
+
         $yaml = new Dumper();
         $yaml->setIndentation($indent);