bug #34801 [String] implement __sleep()/__wakeup() on strings (nicolas-grekas)

This PR was merged into the 5.0 branch.

Discussion
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[String] implement __sleep()/__wakeup() on strings

| Q             | A
| ------------- | ---
| Branch?       | 5.0
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

This resets the transient ignoreCase state on unserialized instances.

Commits
-------

416e40d943 [String] implement __sleep()/__wakeup() on strings

src/Symfony/Component/String/AbstractString.php

@@ -692,6 +692,11 @@ abstract class AbstractString implements \JsonSerializable
         return $str;
     }
 
+    public function __sleep(): array
+    {
+        return ['string'];
+    }
+
     public function __clone()
     {
         $this->ignoreCase = false;

src/Symfony/Component/String/UnicodeString.php

@@ -347,6 +347,11 @@ class UnicodeString extends AbstractUnicodeString
         return $prefix === grapheme_extract($this->string, \strlen($prefix), GRAPHEME_EXTR_MAXBYTES);
     }
 
+    public function __wakeup()
+    {
+        normalizer_is_normalized($this->string) ?: $this->string = normalizer_normalize($this->string);
+    }
+
     public function __clone()
     {
         if (null === $this->ignoreCase) {