bug #18840 [Yaml] properly handle unindented collections (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

[Yaml] properly handle unindented collections

| Q             | A
| ------------- | ---
| Branch?       | 2.3
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8077
| License       | MIT
| Doc PR        |

Commits
-------

717e1a9 [Yaml] properly handle unindented collections

src/Symfony/Component/Yaml/Parser.php

@@ -725,7 +725,7 @@ class Parser
      */
     private function isStringUnIndentedCollectionItem()
     {
-        return 0 === strpos($this->currentLine, '- ');
+        return '-' === rtrim($this->currentLine) || 0 === strpos($this->currentLine, '- ');
     }
 
     /**

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

@@ -557,6 +557,34 @@ EOF
         );
     }
 
+    public function testSequenceInMappingStartedBySingleDashLine()
+    {
+        $yaml = <<<EOT
+a:
+-
+  b:
+  -
+    bar: baz
+- foo
+d: e
+EOT;
+        $expected = array(
+            'a' => array(
+                array(
+                    'b' => array(
+                        array(
+                            'bar' => 'baz',
+                        ),
+                    ),
+                ),
+                'foo',
+            ),
+            'd' => 'e',
+        );
+
+        $this->assertSame($expected, $this->parser->parse($yaml));
+    }
+
     /**
      * @expectedException \Symfony\Component\Yaml\Exception\ParseException
      */