From cb9c4bc3d42b574bdb1cc1017d0f714772cbd897 Mon Sep 17 00:00:00 2001
From: Takuya Aramaki <takaram71@gmail.com>
Date: Wed, 1 Jan 2025 22:20:17 +0900
Subject: [PATCH] Fix GH-11591: AppendIterator fails to iterate with an empty
 generator

---
 Zend/zend_generators.c     |  9 ---------
 Zend/zend_generators.h     |  8 ++++++++
 ext/spl/spl_iterators.c    | 10 ++++++++++
 ext/spl/tests/gh11591.phpt | 17 +++++++++++++++++
 4 files changed, 35 insertions(+), 9 deletions(-)
 create mode 100644 ext/spl/tests/gh11591.phpt

diff --git a/Zend/zend_generators.c b/Zend/zend_generators.c
index a6ea91a7425b9..d8673e7b81336 100644
--- a/Zend/zend_generators.c
+++ b/Zend/zend_generators.c
@@ -872,15 +872,6 @@ ZEND_API void zend_generator_resume(zend_generator *orig_generator) /* {{{ */
 }
 /* }}} */
 
-static inline void zend_generator_ensure_initialized(zend_generator *generator) /* {{{ */
-{
-	if (UNEXPECTED(Z_TYPE(generator->value) == IS_UNDEF) && EXPECTED(generator->execute_data) && EXPECTED(generator->node.parent == NULL)) {
-		zend_generator_resume(generator);
-		generator->flags |= ZEND_GENERATOR_AT_FIRST_YIELD;
-	}
-}
-/* }}} */
-
 static inline void zend_generator_rewind(zend_generator *generator) /* {{{ */
 {
 	zend_generator_ensure_initialized(generator);
diff --git a/Zend/zend_generators.h b/Zend/zend_generators.h
index e7b01fb20ad7f..b3eef02b6948c 100644
--- a/Zend/zend_generators.h
+++ b/Zend/zend_generators.h
@@ -105,6 +105,14 @@ static const uint8_t ZEND_GENERATOR_IN_FIBER          = 0x10;
 void zend_register_generator_ce(void);
 ZEND_API void zend_generator_close(zend_generator *generator, bool finished_execution);
 ZEND_API void zend_generator_resume(zend_generator *generator);
+static inline void zend_generator_ensure_initialized(zend_generator *generator) /* {{{ */
+{
+	if (UNEXPECTED(Z_TYPE(generator->value) == IS_UNDEF) && EXPECTED(generator->execute_data) && EXPECTED(generator->node.parent == NULL)) {
+		zend_generator_resume(generator);
+		generator->flags |= ZEND_GENERATOR_AT_FIRST_YIELD;
+	}
+}
+/* }}} */
 
 ZEND_API void zend_generator_restore_call_stack(zend_generator *generator);
 ZEND_API zend_execute_data* zend_generator_freeze_call_stack(zend_execute_data *execute_data);
diff --git a/ext/spl/spl_iterators.c b/ext/spl/spl_iterators.c
index d4e40bf6b684a..88c25b7ce69c4 100644
--- a/ext/spl/spl_iterators.c
+++ b/ext/spl/spl_iterators.c
@@ -21,6 +21,7 @@
 #include "php.h"
 #include "zend_exceptions.h"
 #include "zend_interfaces.h"
+#include "zend_generators.h"
 #include "ext/pcre/php_pcre.h"
 
 #include "spl_iterators.h"
@@ -2814,6 +2815,15 @@ PHP_METHOD(AppendIterator, append)
 		RETURN_THROWS();
 	}
 
+	if (instanceof_function(Z_OBJCE_P(it), zend_ce_generator)) {
+		zend_generator *gen = (zend_generator*)Z_OBJ_P(it);
+		zend_generator_ensure_initialized(gen);
+		if (gen->execute_data == NULL) {
+			/* Skip an empty generator */
+			return;
+		}
+	}
+
 	SPL_FETCH_AND_CHECK_DUAL_IT(intern, ZEND_THIS);
 
 	if (intern->u.append.iterator->funcs->valid(intern->u.append.iterator) == SUCCESS && spl_dual_it_valid(intern) != SUCCESS) {
diff --git a/ext/spl/tests/gh11591.phpt b/ext/spl/tests/gh11591.phpt
new file mode 100644
index 0000000000000..8c690c2ce915b
--- /dev/null
+++ b/ext/spl/tests/gh11591.phpt
@@ -0,0 +1,17 @@
+--TEST--
+Bug GH-11591 (Inconsistent behaviour with AppendIterator and empty generators)
+--FILE--
+<?php
+function yieldEmpty()
+{
+    yield from [];
+}
+
+$iterator = new AppendIterator();
+$iterator->append(yieldEmpty());
+
+foreach ($iterator as $item) {
+    var_dump($item);
+}
+?>
+--EXPECT--