Fixed bug #78434

The DO_INIT flag, which will skip the first resume on a primed
generator, should always be set when starting to yield from a
new generator, not only when the yield from happens during priming.

Author: nikic

NEWS

@@ -3,6 +3,9 @@ PHP                                                                        NEWS
 
 ?? ??? ????, PHP 7.4.6
 
+- Core:
+  . Fixed bug #78434 (Generator yields no items after valid() call). (Nikita)
+
 - DOM:
   . Fixed bug #78221 (DOMNode::normalize() doesn't remove empty text nodes).
     (cmb)

Zend/tests/generators/bug78434.phpt

@@ -0,0 +1,27 @@
+--TEST--
+Bug #78434: Generator skips first item after valid() call
+--FILE--
+<?php
+
+$function = function () {
+    yield 0;
+};
+
+$wrapper = function () use ($function) {
+    $generator = $function();
+    $generator->valid();
+    yield from $generator;
+
+    $generator = $function();
+    $generator->valid();
+    yield from $generator;
+};
+
+foreach ($wrapper() as $value) {
+    echo $value, "\n";
+}
+
+?>
+--EXPECT--
+0
+0

Zend/tests/generators/yield_from_multi_tree.phpt

@@ -10,9 +10,6 @@ function from($levels) {
 }
 
 function gen($gen, $level) {
-	if ($level % 2) {
-		yield $gen->current();
-	}
 	yield from $gen;
 }
 

Zend/zend_generators.c

@@ -609,6 +609,7 @@ void zend_generator_yield_from(zend_generator *generator, zend_generator *from)
 	generator->node.parent = from;
 	zend_generator_get_current(generator);
 	GC_DELREF(&from->std);
+	generator->flags |= ZEND_GENERATOR_DO_INIT;
 }
 
 ZEND_API zend_generator *zend_generator_update_current(zend_generator *generator, zend_generator *leaf)
@@ -785,6 +786,7 @@ ZEND_API void zend_generator_resume(zend_generator *orig_generator) /* {{{ */
 
 	if (UNEXPECTED((orig_generator->flags & ZEND_GENERATOR_DO_INIT) != 0 && !Z_ISUNDEF(generator->value))) {
 		/* We must not advance Generator if we yield from a Generator being currently run */
+		orig_generator->flags &= ~ZEND_GENERATOR_DO_INIT;
 		return;
 	}
 
@@ -864,15 +866,15 @@ ZEND_API void zend_generator_resume(zend_generator *orig_generator) /* {{{ */
 			goto try_again;
 		}
 	}
+
+	orig_generator->flags &= ~ZEND_GENERATOR_DO_INIT;
 }
 /* }}} */
 
 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)) {
-		generator->flags |= ZEND_GENERATOR_DO_INIT;
 		zend_generator_resume(generator);
-		generator->flags &= ~ZEND_GENERATOR_DO_INIT;
 		generator->flags |= ZEND_GENERATOR_AT_FIRST_YIELD;
 	}
 }