PoC with() / context managers

Author: arnaud-lb

Zend/tests/context_managers/basic.phpt

@@ -0,0 +1,22 @@
+--TEST--
+with() calls enter and exit
+--FILE--
+<?php
+
+require 'basic_manager.inc';
+
+with (new Manager() as $value) {
+    echo "In with() block\n";
+    var_dump($value);
+}
+
+echo "After with() block\n";
+
+?>
+--EXPECTF--
+Manager::enterContext()
+In with() block
+object(stdClass)#%d (0) {
+}
+Manager::exitContext(null)
+After with() block

Zend/tests/context_managers/basic_manager.inc

@@ -0,0 +1,22 @@
+<?php
+
+class Manager implements ContextManager
+{
+    public function __construct(private bool $rethrow = true)
+    {
+    }
+
+    public function enterContext(): mixed
+    {
+        echo __METHOD__, "()\n";
+        return new stdClass;
+    }
+
+    public function exitContext(?\Throwable $e = null): ?bool
+    {
+        echo __METHOD__, "(", ($e ? get_class($e) . '(' . $e->getMessage() . ')' : 'null'), ")\n";
+        return !$this->rethrow;
+    }
+}
+
+?>

Zend/tests/context_managers/exitContext_can_swallow_exception.phpt

@@ -0,0 +1,23 @@
+--TEST--
+with() does not rethrow exception when exitContext() returns true
+--FILE--
+<?php
+
+require 'basic_manager.inc';
+
+with (new Manager(false) as $value) {
+    echo "In with() block\n";
+    var_dump($value);
+    throw new Exception('exception in with block');
+}
+
+echo "After with() block\n";
+
+?>
+--EXPECTF--
+Manager::enterContext()
+In with() block
+object(stdClass)#%d (0) {
+}
+Manager::exitContext(Exception(exception in with block))
+After with() block

Zend/tests/context_managers/variable_is_optional.phpt

@@ -0,0 +1,19 @@
+--TEST--
+Variable on the rhs of 'as' is optional
+--FILE--
+<?php
+
+require 'basic_manager.inc';
+
+with (new Manager()) {
+    echo "In with() block\n";
+}
+
+echo "After with() block\n";
+
+?>
+--EXPECT--
+Manager::enterContext()
+In with() block
+Manager::exitContext(null)
+After with() block

Zend/tests/context_managers/with_calls_exitContext_on_exception.phpt

@@ -0,0 +1,28 @@
+--TEST--
+with() calls exitContext($exception) on exception and re-throws by default
+--FILE--
+<?php
+
+require 'basic_manager.inc';
+
+try {
+    with (new Manager() as $value) {
+        echo "In with() block\n";
+        var_dump($value);
+        throw new Exception('exception in with block');
+    }
+} catch (Exception $e) {
+    echo $e::class, ": ", $e->getMessage(), "\n";
+}
+
+echo "After with() block\n";
+
+?>
+--EXPECTF--
+Manager::enterContext()
+In with() block
+object(stdClass)#%d (0) {
+}
+Manager::exitContext(Exception(exception in with block))
+Exception: exception in with block
+After with() block

Zend/tests/context_managers/with_handles_throwable.phpt

@@ -0,0 +1,28 @@
+--TEST--
+with() handles Throwable
+--FILE--
+<?php
+
+require 'basic_manager.inc';
+
+try {
+    with (new Manager() as $value) {
+        echo "In with() block\n";
+        var_dump($value);
+        throw new Error('error in with block');
+    }
+} catch (Error $e) {
+    echo $e::class, ": ", $e->getMessage(), "\n";
+}
+
+echo "After with() block\n";
+
+?>
+--EXPECTF--
+Manager::enterContext()
+In with() block
+object(stdClass)#%d (0) {
+}
+Manager::exitContext(Error(error in with block))
+Error: error in with block
+After with() block

Zend/zend_ast.c

@@ -400,6 +400,43 @@ ZEND_API zend_ast * ZEND_FASTCALL zend_ast_create_list_2(zend_ast_kind kind, zen
 
 	return ast;
 }
+
+ZEND_API zend_ast * ZEND_FASTCALL zend_ast_create_list_3(zend_ast_kind kind, zend_ast *child1, zend_ast *child2, zend_ast *child3) {
+	zend_ast *ast;
+	zend_ast_list *list;
+	uint32_t lineno;
+
+	ast = zend_ast_alloc(zend_ast_list_size(4));
+	list = (zend_ast_list *) ast;
+	list->kind = kind;
+	list->attr = 0;
+	list->children = 3;
+	list->child[0] = child1;
+	list->child[1] = child2;
+	list->child[2] = child3;
+	if (child1) {
+		lineno = zend_ast_get_lineno(child1);
+		if (lineno > CG(zend_lineno)) {
+			lineno = CG(zend_lineno);
+		}
+	} else if (child2) {
+		lineno = zend_ast_get_lineno(child2);
+		if (lineno > CG(zend_lineno)) {
+			lineno = CG(zend_lineno);
+		}
+	} else if (child3) {
+		lineno = zend_ast_get_lineno(child3);
+		if (lineno > CG(zend_lineno)) {
+			lineno = CG(zend_lineno);
+		}
+	} else {
+		list->children = 0;
+		lineno = CG(zend_lineno);
+	}
+	list->lineno = lineno;
+
+	return ast;
+}
 #else
 static zend_ast *zend_ast_create_from_va_list(zend_ast_kind kind, zend_ast_attr attr, va_list va) {
 	uint32_t i, children = kind >> ZEND_AST_NUM_CHILDREN_SHIFT;

Zend/zend_ast.h

@@ -166,6 +166,7 @@ enum _zend_ast_kind {
 	ZEND_AST_PROP_GROUP,
 	ZEND_AST_CONST_ELEM,
 	ZEND_AST_CLASS_CONST_GROUP,
+	ZEND_AST_WITH,
 
 	// Pseudo node for initializing enums
 	ZEND_AST_CONST_ENUM_INIT,
@@ -306,6 +307,7 @@ static zend_always_inline zend_ast * zend_ast_create_ex_5(zend_ast_kind kind, ze
 ZEND_API zend_ast * ZEND_FASTCALL zend_ast_create_list_0(zend_ast_kind kind);
 ZEND_API zend_ast * ZEND_FASTCALL zend_ast_create_list_1(zend_ast_kind kind, zend_ast *child);
 ZEND_API zend_ast * ZEND_FASTCALL zend_ast_create_list_2(zend_ast_kind kind, zend_ast *child1, zend_ast *child2);
+ZEND_API zend_ast * ZEND_FASTCALL zend_ast_create_list_3(zend_ast_kind kind, zend_ast *child1, zend_ast *child2, zend_ast *child3);
 
 # define zend_ast_create(...) \
 	ZEND_AST_SPEC_CALL(zend_ast_create, __VA_ARGS__)

Zend/zend_builtin_functions.c

@@ -34,10 +34,13 @@
 
 /* }}} */
 
+ZEND_API zend_class_entry *zend_ce_context_manager = NULL;
+
 ZEND_MINIT_FUNCTION(core) { /* {{{ */
 	zend_register_default_classes();
 
 	zend_standard_class_def = register_class_stdClass();
+	zend_ce_context_manager = register_class_ContextManager();
 
 	return SUCCESS;
 }

Zend/zend_builtin_functions.h

@@ -23,6 +23,7 @@
 #include "zend_types.h"
 
 typedef struct _zval_struct zval;
+extern ZEND_API zend_class_entry *zend_ce_context_manager;
 
 zend_result zend_startup_builtin_functions(void);