[RFC] Class Friendship

Zend/tests/friends/friend_basic_001.phpt

@@ -0,0 +1,46 @@
+--TEST--
+A class can declare another class as a friend so that it may access protected and private properties
+--FILE--
+<?php
+
+class Person
+{
+	friend PersonFormatter;
+
+	private $firstName;
+	private $lastName;
+
+	public function __construct($firstName, $lastName)
+	{
+		$this->firstName = $firstName;
+		$this->lastName = $lastName;
+	}
+
+	public function format()
+	{
+		return new PersonFormatter($this);
+	}
+}
+
+class PersonFormatter
+{
+	private $person;
+
+	public function __construct(Person $person)
+	{
+		$this->person = $person;
+	}
+
+	public function getFullName()
+	{
+		return $this->person->firstName . ' ' . $this->person->lastName;
+	}
+}
+
+$person = new Person('Alice', 'Wonderland');
+$formatter = $person->format();
+
+var_dump($formatter->getFullName());
+?>
+--EXPECTF--
+string(%d) "Alice Wonderland"

Zend/tests/friends/friend_basic_002.phpt

@@ -0,0 +1,44 @@
+--TEST--
+A class can declare multiple classes as friend
+--FILE--
+<?php
+
+class PartyHost
+{
+	friend PartyGoer, Bouncer;
+
+	private $name;
+
+	public function __construct($name)
+	{
+		$this->name = $name;
+	}
+}
+
+class PartyGoer
+{
+	public function greet(PartyHost $person)
+	{
+		echo "Your name was {$person->name}, right? Nice party!" . PHP_EOL;
+	}
+}
+
+class Bouncer
+{
+	public function greet(PartyHost $person)
+	{
+		echo "Hey {$person->name}! If you need backup, let me know." . PHP_EOL;
+	}
+}
+
+$host = new PartyHost('Dustin');
+$attendee = new PartyGoer();
+$bouncer = new Bouncer();
+
+$attendee->greet($host);
+$bouncer->greet($host);
+
+?>
+--EXPECT--
+Your name was Dustin, right? Nice party!
+Hey Dustin! If you need backup, let me know.

Zend/tests/friends/friend_inheritance_001.phpt

@@ -0,0 +1,41 @@
+--TEST--
+A friend of class Base is not automatically a friend of class Derived and vice-versa
+--FILE--
+<?php
+
+class Base
+{
+	friend Friendly;
+
+	protected $property = 'base';
+}
+
+class Derived extends Base
+{
+	protected $property = 'derived';
+}
+
+class Friendly
+{
+	public function touch(Base $base)
+	{
+		echo $base->property . PHP_EOL;
+	}
+}
+
+$base = new Base();
+$derived = new Derived();
+$friend = new Friendly();
+
+$friend->touch($base);
+$friend->touch($derived);
+
+?>
+--EXPECTF--
+base
+
+Fatal error: Uncaught Error: Cannot access protected property Derived::$property in %s:%d
+Stack trace:
+#0 %s(%d): Friendly->touch(Object(Derived))
+#1 {main}
+  thrown in %s on line %d

Zend/tests/friends/friend_inheritance_002.phpt

@@ -0,0 +1,42 @@
+--TEST--
+Friendship is not transitive. If Base is a friend of another class, Derived is not automatically a friend.
+--FILE--
+<?php
+
+class Subject
+{
+	friend Base;
+
+	protected $property = 'subject';
+}
+
+class Base
+{
+	protected $friend;
+
+	public function __construct(Subject $subject)
+	{
+		$this->friend = $subject;
+	}
+}
+
+class Derived extends Base
+{
+	public function touch()
+	{
+		echo $this->friend->property . PHP_EOL;
+	}
+}
+
+$subject = new Subject();
+$derived = new Derived($subject);
+
+$derived->touch();
+
+?>
+--EXPECTF--
+Fatal error: Uncaught Error: Cannot access protected property Subject::$property in %s:%d
+Stack trace:
+#0 %s(%d): Derived->touch()
+#1 {main}
+  thrown in %s on line %d

Zend/tests/friends/friend_inheritance_003.phpt

@@ -0,0 +1,49 @@
+--TEST--
+Access due to friendship is inherited
+--FILE--
+<?php
+
+class Base
+{
+	private $secret = 'secret';
+	protected $override = 'override';
+}
+
+class Derived extends Base
+{
+	friend Friendly;
+
+	protected $derived = 'derived';
+
+	public function touch()
+	{
+		echo $this->secret . PHP_EOL;
+    }
+}
+
+class Friendly
+{
+	public function touch(Derived $derived)
+	{
+		echo $derived->derived . PHP_EOL;    // Allowed via normal friend functionality
+		echo $derived->override . PHP_EOL;   // Allowed because inherited and accessible by Derived
+
+		echo $derived->secret . PHP_EOL;     // Dis-allowed because not accessible by Derived
+											 // In this case, it will behave just as if the derived itself
+											 // attempted to access the private property from base
+	}
+}
+
+$derived = new Derived();
+
+$derived->touch();
+(new Friendly())->touch($derived);
+
+?>
+--EXPECTF--
+Notice: Undefined property: Derived::$secret in %s on line %d
+
+derived
+override
+
+Notice: Undefined property: Derived::$secret in %s on line %d

Zend/zend.h

@@ -156,11 +156,13 @@ struct _zend_class_entry {
 
 	uint32_t num_interfaces;
 	uint32_t num_traits;
+	uint32_t num_friends;
 	zend_class_entry **interfaces;
 
 	zend_class_entry **traits;
 	zend_trait_alias **trait_aliases;
 	zend_trait_precedence **trait_precedences;
+	zend_class_entry **friends;
 
 	union {
 		struct {

Zend/zend_ast.h

@@ -89,6 +89,7 @@ enum _zend_ast_kind {
 	ZEND_AST_POST_INC,
 	ZEND_AST_POST_DEC,
 	ZEND_AST_YIELD_FROM,
+	ZEND_AST_FRIEND,
 
 	ZEND_AST_GLOBAL,
 	ZEND_AST_UNSET,

Zend/zend_compile.c

@@ -1211,6 +1211,7 @@ void zend_do_early_binding(void) /* {{{ */
 		case ZEND_VERIFY_ABSTRACT_CLASS:
 		case ZEND_ADD_INTERFACE:
 		case ZEND_ADD_TRAIT:
+		case ZEND_ADD_FRIEND:
 		case ZEND_BIND_TRAITS:
 			/* We currently don't early-bind classes that implement interfaces */
 			/* Classes with traits are handled exactly the same, no early-bind here */
@@ -1758,6 +1759,8 @@ ZEND_API void zend_initialize_class_data(zend_class_entry *ce, zend_bool nullify
 		ce->traits = NULL;
 		ce->trait_aliases = NULL;
 		ce->trait_precedences = NULL;
+		ce->num_friends = 0;
+		ce->friends = NULL;
 		ce->serialize = NULL;
 		ce->unserialize = NULL;
 		ce->serialize_func = NULL;
@@ -6251,6 +6254,26 @@ void zend_compile_use_trait(zend_ast *ast) /* {{{ */
 }
 /* }}} */
 
+void zend_compile_friend(zend_ast *ast) /* {{{ */
+{
+	zend_ast_list *friends = zend_ast_get_list(ast->child[0]);
+	zend_class_entry *ce = CG(active_class_entry);
+	zend_op *opline;
+	uint32_t i;
+
+	for (i = 0; i < friends->children; ++i) {
+		zend_ast *friend_ast = friends->child[i];
+
+	 	opline = zend_emit_op(NULL, ZEND_ADD_FRIEND, &FC(implementing_class), NULL);
+		opline->op2_type = IS_CONST;
+		opline->op2.constant = zend_add_class_name_literal(CG(active_op_array), 
+			zend_resolve_class_name_ast(friend_ast));
+
+	 	ce->num_friends++;
+	}
+}
+/* }}} */
+
 void zend_compile_implements(znode *class_node, zend_ast *ast) /* {{{ */
 {
 	zend_ast_list *list = zend_ast_get_list(ast);
@@ -6462,6 +6485,11 @@ void zend_compile_class_decl(zend_ast *ast) /* {{{ */
 		zend_emit_op(NULL, ZEND_BIND_TRAITS, &declare_node, NULL);
 	}
 
+	if (ce->num_friends > 0) {
+		ce->friends = NULL;
+		ce->num_friends = 0;
+	}
+
 	if (implements_ast) {
 		zend_compile_implements(&declare_node, implements_ast);
 	}
@@ -8199,6 +8227,9 @@ void zend_compile_stmt(zend_ast *ast) /* {{{ */
 		case ZEND_AST_USE_TRAIT:
 			zend_compile_use_trait(ast);
 			break;
+		case ZEND_AST_FRIEND:
+			zend_compile_friend(ast);
+			break;	
 		case ZEND_AST_CLASS:
 			zend_compile_class_decl(ast);
 			break;

Zend/zend_inheritance.c

@@ -1102,6 +1102,32 @@ ZEND_API void zend_do_implement_trait(zend_class_entry *ce, zend_class_entry *tr
 }
 /* }}} */
 
+ZEND_API void zend_do_implement_friend(zend_class_entry *ce, zend_class_entry *friend) /* {{{ */
+{
+	uint32_t i, ignore = 0;
+	uint32_t current_friend_num = ce->num_friends;
+	uint32_t parent_friend_num  = ce->parent ? ce->parent->num_friends : 0;
+
+	for (i = 0; i < ce->num_friends; i++) {
+		if (ce->friends[i] == NULL) {
+			memmove(ce->friends + i, ce->friends + i + 1, sizeof(zend_class_entry*) * (--ce->num_friends - i));
+			i--;
+		} else if (ce->friends[i] == friend) {
+			if (i < parent_friend_num) {
+				ignore = 1;
+			}
+		}
+	}
+
+	if (!ignore) {
+		if (ce->num_friends >= current_friend_num) {
+			ce->friends = (zend_class_entry **) erealloc(ce->friends, sizeof(zend_class_entry *) * (++current_friend_num));
+		}
+		ce->friends[ce->num_friends++] = friend;
+	}
+}
+/* }}} */
+
 static zend_bool zend_traits_method_compatibility_check(zend_function *fn, zend_function *other_fn) /* {{{ */
 {
 	uint32_t    fn_flags = fn->common.scope->ce_flags;

Zend/zend_inheritance.h

@@ -30,6 +30,8 @@ ZEND_API void zend_do_implement_interface(zend_class_entry *ce, zend_class_entry
 ZEND_API void zend_do_implement_trait(zend_class_entry *ce, zend_class_entry *trait);
 ZEND_API void zend_do_bind_traits(zend_class_entry *ce);
 
+ZEND_API void zend_do_implement_friend(zend_class_entry *ce, zend_class_entry *friend);
+
 ZEND_API void zend_do_inheritance(zend_class_entry *ce, zend_class_entry *parent_ce);
 void zend_do_early_binding(void);
 

Zend/zend_language_parser.y

@@ -174,6 +174,7 @@ static YYSIZE_T zend_yytnamerr(char*, const char*);
 %token T_FINALLY    "finally (T_FINALLY)"
 %token T_THROW      "throw (T_THROW)"
 %token T_USE        "use (T_USE)"
+%token T_FRIEND     "friend (T_FRIEND)"
 %token T_INSTEADOF  "insteadof (T_INSTEADOF)"
 %token T_GLOBAL     "global (T_GLOBAL)"
 %token T_STATIC     "static (T_STATIC)"
@@ -271,7 +272,7 @@ reserved_non_modifiers:
 	  T_INCLUDE | T_INCLUDE_ONCE | T_EVAL | T_REQUIRE | T_REQUIRE_ONCE | T_LOGICAL_OR | T_LOGICAL_XOR | T_LOGICAL_AND
 	| T_INSTANCEOF | T_NEW | T_CLONE | T_EXIT | T_IF | T_ELSEIF | T_ELSE | T_ENDIF | T_ECHO | T_DO | T_WHILE | T_ENDWHILE
 	| T_FOR | T_ENDFOR | T_FOREACH | T_ENDFOREACH | T_DECLARE | T_ENDDECLARE | T_AS | T_TRY | T_CATCH | T_FINALLY
-	| T_THROW | T_USE | T_INSTEADOF | T_GLOBAL | T_VAR | T_UNSET | T_ISSET | T_EMPTY | T_CONTINUE | T_GOTO
+	| T_THROW | T_USE | T_FRIEND | T_INSTEADOF | T_GLOBAL | T_VAR | T_UNSET | T_ISSET | T_EMPTY | T_CONTINUE | T_GOTO
 	| T_FUNCTION | T_CONST | T_RETURN | T_PRINT | T_YIELD | T_LIST | T_SWITCH | T_ENDSWITCH | T_CASE | T_DEFAULT | T_BREAK
 	| T_ARRAY | T_CALLABLE | T_EXTENDS | T_IMPLEMENTS | T_NAMESPACE | T_TRAIT | T_INTERFACE | T_CLASS
 	| T_CLASS_C | T_TRAIT_C | T_FUNC_C | T_METHOD_C | T_LINE | T_FILE | T_DIR | T_NS_C
@@ -724,6 +725,8 @@ class_statement:
 			{ $$ = $3; $$->attr = $1; }
 	|	T_USE name_list trait_adaptations
 			{ $$ = zend_ast_create(ZEND_AST_USE_TRAIT, $2, $3); }
+	|	T_FRIEND name_list ';'
+			{ $$ = zend_ast_create(ZEND_AST_FRIEND, $2); }
 	|	method_modifiers function returns_ref identifier backup_doc_comment '(' parameter_list ')'
 		return_type backup_fn_flags method_body backup_fn_flags
 			{ $$ = zend_ast_create_decl(ZEND_AST_METHOD, $3 | $1 | $12, $2, $5,