bug #21084 [Yaml] handle empty lines inside unindented collection (xabbuh)

This PR was merged into the 2.7 branch.

Discussion
----------

[Yaml] handle empty lines inside unindented collection

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #21005
| License       | MIT
| Doc PR        |

Commits
-------

bbfe6f73b5 handle empty lines inside unindented collection

src/Symfony/Component/Yaml/Parser.php

@@ -423,7 +423,7 @@ class Parser
 
             $previousLineIndentation = $indent;
 
-            if ($isItUnindentedCollection && !$this->isStringUnIndentedCollectionItem() && $newIndent === $indent) {
+            if ($isItUnindentedCollection && !$this->isCurrentLineEmpty() && !$this->isStringUnIndentedCollectionItem() && $newIndent === $indent) {
                 $this->moveToPreviousLine();
                 break;
             }

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

@@ -189,6 +189,22 @@ EOF;
         );
         $tests['Literal block chomping clip with multiple trailing newlines'] = array($expected, $yaml);
 
+        $yaml = <<<'EOF'
+foo:
+- bar: |
+    one
+
+    two
+EOF;
+        $expected = array(
+            'foo' => array(
+                array(
+                    'bar' => "one\n\ntwo",
+                ),
+            ),
+        );
+        $tests['Literal block chomping clip with embedded blank line inside unindented collection'] = array($expected, $yaml);
+
         $yaml = <<<'EOF'
 foo: |
     one