feature symfony#59325 [Config] Add ifFalse() (OskarStark)

This PR was squashed before being merged into the 7.3 branch.

Discussion
----------

[Config] Add `ifFalse()`

| Q             | A
| ------------- | ---
| Branch?       | 7.3
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Issues        | --
| License       | MIT

Spottet while working on
* php-llm/llm-chain-bundle#55

It is much easier to use like IMHO:
```php
->ifTrue(fn ($v) => false === $v)
```

Commits
-------

b85beb6 [Config] Add `ifFalse()`

Author: fabpot

src/Symfony/Component/Config/CHANGELOG.md

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+7.3
+---
+
+ * Add `ExprBuilder::ifFalse()`
+
 7.2
 ---
 

src/Symfony/Component/Config/Definition/Builder/ExprBuilder.php

@@ -67,6 +67,21 @@ public function ifTrue(?\Closure $closure = null): static
         return $this;
     }
 
+    /**
+     * Sets a closure to use as tests.
+     *
+     * The default one tests if the value is false.
+     *
+     * @return $this
+     */
+    public function ifFalse(?\Closure $closure = null): static
+    {
+        $this->ifPart = $closure ?? static fn ($v) => false === $v;
+        $this->allowedTypes = self::TYPE_ANY;
+
+        return $this;
+    }
+
     /**
      * Tests if the value is a string.
      *

src/Symfony/Component/Config/Tests/Definition/Builder/ExprBuilderTest.php

@@ -49,6 +49,27 @@ public function testIfTrueExpression()
         $this->assertFinalizedValueIs('value', $test);
     }
 
+    public function testIfFalseExpression()
+    {
+        $test = $this->getTestBuilder()
+            ->ifFalse()
+            ->then($this->returnClosure('new_value'))
+        ->end();
+        $this->assertFinalizedValueIs('new_value', $test, ['key' => false]);
+
+        $test = $this->getTestBuilder()
+            ->ifFalse(fn () => true)
+            ->then($this->returnClosure('new_value'))
+        ->end();
+        $this->assertFinalizedValueIs('new_value', $test);
+
+        $test = $this->getTestBuilder()
+            ->ifFalse(fn () => false)
+            ->then($this->returnClosure('new_value'))
+        ->end();
+        $this->assertFinalizedValueIs('value', $test);
+    }
+
     public function testIfStringExpression()
     {
         $test = $this->getTestBuilder()