bug #21279 #20411 fix Yaml parsing for very long quoted strings (RichardBradley)

This PR was merged into the 2.7 branch.

Discussion
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#20411 fix Yaml parsing for very long quoted strings

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #20411
| License       | MIT
| Doc PR        | no

This fixes #20411, a YAML string with too many backslash escapes can trigger a `PREG_BACKTRACK_LIMIT_ERROR` error in the Yaml parser.

There should be no behavioural change other than the bug fix

I have included a test which fails before this fix and passes after this fix.

Commits
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51bca66 #20411 fix Yaml parsing for very long quoted strings

src/Symfony/Component/Yaml/Inline.php

@@ -21,7 +21,7 @@ use Symfony\Component\Yaml\Exception\DumpException;
  */
 class Inline
 {
-    const REGEX_QUOTED_STRING = '(?:"([^"\\\\]*(?:\\\\.[^"\\\\]*)*)"|\'([^\']*(?:\'\'[^\']*)*)\')';
+    const REGEX_QUOTED_STRING = '(?:"([^"\\\\]*+(?:\\\\.[^"\\\\]*+)*+)"|\'([^\']*+(?:\'\'[^\']*+)*+)\')';
 
     private static $exceptionOnInvalidType = false;
     private static $objectSupport = false;

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

@@ -410,4 +410,14 @@ class InlineTest extends \PHPUnit_Framework_TestCase
     {
         Inline::parse('{this, is not, supported}');
     }
+
+    public function testVeryLongQuotedStrings()
+    {
+        $longStringWithQuotes = str_repeat("x\r\n\\\"x\"x", 1000);
+
+        $yamlString = Inline::dump(array('longStringWithQuotes' => $longStringWithQuotes));
+        $arrayFromYaml = Inline::parse($yamlString);
+
+        $this->assertEquals($longStringWithQuotes, $arrayFromYaml['longStringWithQuotes']);
+    }
 }