bug #13262 [Yaml] Improve YAML boolean escaping (petert82, larowlan)

This PR was merged into the 2.3 branch.

Discussion
----------

[Yaml] Improve YAML boolean escaping

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #13209
| License       | MIT
| Doc PR        | None

This PR ensures that PHP [values which would be interpreted as booleans][1] in older versions of the YAML spec are escaped with single quotes when dumped by the Dumper.

For example, dumping this:

```php
array(
    'country_code' => 'no',
    'speaks_norwegian' => 'y',
    'heating' => 'on',
)
```

Will produce this YAML:

```yaml
country_code: 'no'
speaks_norwegian: 'y'
heating: 'on'
```

[1]: http://yaml.org/type/bool.html

Commits
-------

8fa056b Inline private 'is quoting required' methods in Escaper
afe827a Merge pull request #2 from larowlan/patch-2
a0ec0fe Add comment as requested
1e0633e Merge pull request #1 from larowlan/patch-1
81a8090 Remove duplicate 'require'
3760e67 [Yaml] Improve YAML boolean escaping

src/Symfony/Component/Yaml/Escaper.php

@@ -72,7 +72,15 @@ public static function escapeWithDoubleQuotes($value)
      */
     public static function requiresSingleQuoting($value)
     {
-        return preg_match('/[ \s \' " \: \{ \} \[ \] , & \* \# \?] | \A[ \- ? | < > = ! % @ ` ]/x', $value);
+        // Determines if the PHP value contains any single characters that would
+        // cause it to require single quoting in YAML.
+        if (preg_match('/[ \s \' " \: \{ \} \[ \] , & \* \# \?] | \A[ \- ? | < > = ! % @ ` ]/x', $value)) {
+            return true;
+        }
+
+        // Determines if a PHP value is entirely composed of a value that would
+        // require single quoting in YAML.
+        return in_array(strtolower($value), array('null', '~', 'true', 'false', 'y', 'n', 'yes', 'no', 'on', 'off'));
     }
 
     /**

src/Symfony/Component/Yaml/Inline.php

@@ -135,12 +135,10 @@ public static function dump($value, $exceptionOnInvalidType = false, $objectSupp
             case Escaper::requiresDoubleQuoting($value):
                 return Escaper::escapeWithDoubleQuotes($value);
             case Escaper::requiresSingleQuoting($value):
+            case preg_match(self::getTimestampRegex(), $value):
                 return Escaper::escapeWithSingleQuotes($value);
             case '' == $value:
                 return "''";
-            case preg_match(self::getTimestampRegex(), $value):
-            case in_array(strtolower($value), array('null', '~', 'true', 'false')):
-                return "'$value'";
             default:
                 return $value;
         }

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

@@ -190,6 +190,14 @@ protected function getTestsForParse()
             "'#cfcfcf'" => '#cfcfcf',
             '::form_base.html.twig' => '::form_base.html.twig',
 
+            // Pre-YAML-1.2 booleans
+            "'y'" => 'y',
+            "'n'" => 'n',
+            "'yes'" => 'yes',
+            "'no'" => 'no',
+            "'on'" => 'on',
+            "'off'" => 'off',
+
             '2007-10-30' => mktime(0, 0, 0, 10, 30, 2007),
             '2007-10-30T02:59:43Z' => gmmktime(2, 59, 43, 10, 30, 2007),
             '2007-10-30 02:59:43 Z' => gmmktime(2, 59, 43, 10, 30, 2007),
@@ -257,6 +265,14 @@ protected function getTestsForDump()
             "'-dash'" => '-dash',
             "'-'" => '-',
 
+            // Pre-YAML-1.2 booleans
+            "'y'" => 'y',
+            "'n'" => 'n',
+            "'yes'" => 'yes',
+            "'no'" => 'no',
+            "'on'" => 'on',
+            "'off'" => 'off',
+
             // sequences
             '[foo, bar, false, null, 12]' => array('foo', 'bar', false, null, 12),
             '[\'foo,bar\', \'foo bar\']' => array('foo,bar', 'foo bar'),