[RFC] Allow hooks for backed readonly properties

NEWS

@@ -53,6 +53,7 @@ PHP                                                                        NEWS
     evaluation) and GH-18464 (Recursion protection for deprecation constants not
     released on bailout). (DanielEScherzer and ilutov)
   . Fixed AST printing for immediately invoked Closure. (Dmitrii Derepko)
+  . Property hooks are now allowed on backed readonly properties. (Crell, NickSdot and iluuu1994)
 
 - Curl:
   . Added curl_multi_get_handles(). (timwolla)

UPGRADING

@@ -144,6 +144,8 @@ PHP 8.5 UPGRADE NOTES
     RFC: https://wiki.php.net/rfc/attributes-on-constants
   . The #[\Deprecated] attribute can now be used on constants.
     RFC: https://wiki.php.net/rfc/attributes-on-constants
+  . Property hooks are now allowed on backed readonly properties.
+    RFC: https://wiki.php.net/rfc/readonly_hooks
 
 - Curl:
   . Added support for share handles that are persisted across multiple PHP

Zend/tests/property_hooks/readonly_class_property_backed.phpt

@@ -0,0 +1,41 @@
+--TEST--
+Backed property in readonly class may have hooks
+--FILE--
+<?php
+
+// readonly class
+readonly class Test {
+    public int $prop {
+        get => $this->prop;
+        set => $value;
+    }
+
+    public function __construct(int $v) {
+        $this->prop = $v;
+    }
+
+    public function set($v)
+    {
+         $this->prop = $v;
+    }
+}
+
+$t = new Test(42);
+var_dump($t->prop);
+try {
+    $t->set(43);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+try {
+    $t->prop = 43;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+var_dump($t->prop);
+?>
+--EXPECT--
+int(42)
+Cannot modify readonly property Test::$prop
+Cannot modify protected(set) readonly property Test::$prop from global scope
+int(42)

Zend/tests/property_hooks/readonly_class_property_backed_inheritance_1.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Non-readonly class cannot extend readonly class
+--FILE--
+<?php
+
+readonly class ParentClass {
+    public int $prop;
+}
+
+class Test extends ParentClass {
+    public function __construct(
+        public int $prop {
+            get => $this->prop;
+            set => $value;
+        }
+    ) {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Non-readonly class Test cannot extend readonly class ParentClass in %s on line %d

Zend/tests/property_hooks/readonly_class_property_backed_inheritance_2.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Readonly class cannot extend non-readonly class
+--FILE--
+<?php
+
+class ParentClass {
+    public int $prop;
+}
+
+readonly class Test extends ParentClass {
+    public function __construct(
+        public int $prop {
+            get => $this->prop;
+            set => $value;
+        }
+    ) {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Readonly class Test cannot extend non-readonly class ParentClass in %s on line %d

Zend/tests/property_hooks/readonly_class_property_backed_promoted.phpt

@@ -0,0 +1,40 @@
+--TEST--
+Backed promoted property in readonly class may have hooks
+--FILE--
+<?php
+
+// readonly class, promoted
+readonly class Test {
+    public function __construct(
+        public int $prop {
+            get => $this->prop;
+            set => $value;
+        }
+    ) {}
+
+    public function set($v)
+    {
+         $this->prop = $v;
+    }
+}
+
+$t = new Test(42);
+var_dump($t->prop);
+try {
+    $t->set(43);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+try {
+    $t->prop = 43;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+var_dump($t->prop);
+?>
+--EXPECT--
+int(42)
+Cannot modify readonly property Test::$prop
+Cannot modify protected(set) readonly property Test::$prop from global scope
+int(42)
+

Zend/tests/property_hooks/readonly_class_property_virtual_promoted.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Virtual promoted property in readonly class cannot have hooks
+--FILE--
+<?php
+
+readonly class Test {
+    public function __construct(
+        public int $prop {
+            get => 42;
+        }
+    ) {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Hooked virtual properties cannot be readonly in %s on line %d

Zend/tests/property_hooks/readonly_lazy.phpt

@@ -0,0 +1,105 @@
+--TEST--
+Readonly classes can be constructed via reflection by ORM
+--FILE--
+<?php
+
+interface DbConnection {
+   public function loadCategory(string $id): Category;
+}
+
+class Category {
+   public function __construct(public string $name) {}
+}
+
+class MockDbConnection implements DbConnection {
+   public function loadCategory(string $id): Category {
+       echo "hit database\n";
+       return new Category("Category {$id}");
+   }
+}
+
+readonly class Product
+{
+    public function __construct(
+        public string $name,
+        public float $price,
+        public Category $category,
+    ) {}
+}
+
+readonly class LazyProduct extends Product
+{
+   private DbConnection $dbApi;
+
+   private string $categoryId;
+
+   public Category $category {
+       get {
+           return $this->category ??= $this->dbApi->loadCategory($this->categoryId);
+       }
+   }
+}
+
+$reflect = new ReflectionClass(LazyProduct::class);
+$product = $reflect->newInstanceWithoutConstructor();
+
+$nameProperty = $reflect->getProperty('name');
+$nameProperty->setAccessible(true);
+$nameProperty->setValue($product, 'Iced Chocolate');
+
+$priceProperty = $reflect->getProperty('price');
+$priceProperty->setAccessible(true);
+$priceProperty->setValue($product, 1.99);
+
+$db = $reflect->getProperty('dbApi');
+$db->setAccessible(true);
+$db->setValue($product, new MockDbConnection());
+
+$categoryId = $reflect->getProperty('categoryId');
+$categoryId->setAccessible(true);
+$categoryId->setValue($product, '42');
+
+// lazy loading, hit db
+$category1 = $product->category;
+echo $category1->name . "\n";
+
+// cached category returned
+$category2 = $product->category;
+echo $category2->name . "\n";
+
+// same category instance returned
+var_dump($category1 === $category2);
+
+// can't be wrong, huh?
+var_dump($product);
+
+// cannot set twice
+try {
+    $categoryId->setValue($product, '420');
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+?>
+--EXPECT--
+hit database
+Category 42
+Category 42
+bool(true)
+object(LazyProduct)#2 (5) {
+  ["name"]=>
+  string(14) "Iced Chocolate"
+  ["price"]=>
+  float(1.99)
+  ["category"]=>
+  object(Category)#8 (1) {
+    ["name"]=>
+    string(11) "Category 42"
+  }
+  ["dbApi":"LazyProduct":private]=>
+  object(MockDbConnection)#6 (0) {
+  }
+  ["categoryId":"LazyProduct":private]=>
+  string(2) "42"
+}
+Cannot modify readonly property LazyProduct::$categoryId