From: Fabrice Bellard <fabrice@bellard.org>
Date: Mon, 26 Oct 2026 15:00:14 +0000 (+0100)
Subject: Await the async iterator return() when a for-await loop breaks (Divy Srivastava)
X-Git-Url: https://git.kaiwu.me/?a=commitdiff_plain;h=1ec58aaa769a992213ec2b871b0228074169904b;p=quickjs.git

Await the async iterator return() when a for-await loop breaks (Divy Srivastava)
---

diff --git a/quickjs.c b/quickjs.c
index c564fdb..98bb3ed 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -17086,6 +17086,16 @@ static __exception int js_iterator_get_value_done(JSContext *ctx, JSValue *sp)
     sp[-2] = JS_NewCatchOffset(ctx, 0); 
     sp[-1] = value;
     sp[0] = JS_NewBool(ctx, done);
+    if (done) {
+        /* Iterator exhausted via {done:true}: drop the iterator object (stack
+           layout at the for-await `next` call is iter_obj,next,catch_offset,result
+           so iter_obj is sp[-4]) so the trailing OP_iterator_close skips calling
+           return(). Mirrors js_for_of_next, which nulls the iterator on done.
+           Per spec AsyncIteratorClose must NOT run on normal completion. This op
+           is emitted only by the for-await-of loop, so the layout is fixed. */
+        JS_FreeValue(ctx, sp[-4]);
+        sp[-4] = JS_UNDEFINED;
+    }
     return 0;
 }
 
@@ -22350,6 +22360,7 @@ typedef struct BlockEnv {
     int using_label_catch;
     int using_label_end;
     uint8_t has_iterator : 1;
+    uint8_t is_async_iterator : 1;
     uint8_t is_regular_stmt : 1; /* i.e. not a loop statement */
     uint8_t has_using : 1; /* the block contains a using declaration */
     uint8_t is_await_using : 1; /* the block has await using declarations */
@@ -28836,6 +28847,7 @@ static void push_break_entry(JSFunctionDef *fd, BlockEnv *be,
     be->label_finally = -1;
     be->scope_level = fd->scope_level;
     be->has_iterator = FALSE;
+    be->is_async_iterator = FALSE;
     be->is_regular_stmt = FALSE;
     be->has_using = FALSE;
     be->is_await_using = FALSE;
@@ -28906,6 +28918,51 @@ static void pop_break_entry(JSParseState *s)
     fd->top_break = be->prev;
 }
 
+static void emit_iterator_close(JSParseState *s, BOOL is_async,
+                                BOOL preserve_completion)
+{
+    int label_no_return, label_done;
+
+    if (!is_async) {
+        if (preserve_completion) {
+            emit_op(s, OP_rot3r);
+            emit_op(s, OP_undefined); /* dummy catch offset */
+        }
+        emit_op(s, OP_iterator_close);
+        return;
+    }
+
+    if (preserve_completion) {
+        /* iter_obj next completion -> completion iter_obj */
+        emit_op(s, OP_nip);
+        emit_op(s, OP_swap);
+    } else {
+        /* iter_obj next catch_offset -> iter_obj */
+        emit_op(s, OP_drop);
+        emit_op(s, OP_drop);
+    }
+
+    emit_op(s, OP_dup);
+    emit_op(s, OP_is_undefined);
+    label_done = emit_goto(s, OP_if_true, -1);
+
+    emit_op(s, OP_get_field2);
+    emit_atom(s, JS_ATOM_return);
+    /* completion? iter_obj return_func */
+    emit_op(s, OP_dup);
+    emit_op(s, OP_is_undefined_or_null);
+    label_no_return = emit_goto(s, OP_if_true, -1);
+    emit_op(s, OP_call_method);
+    emit_u16(s, 0);
+    emit_op(s, OP_await);
+    emit_goto(s, OP_goto, label_done);
+    emit_label(s, label_no_return);
+    emit_op(s, OP_drop);
+
+    emit_label(s, label_done);
+    emit_op(s, OP_drop);
+}
+
 static __exception int emit_break(JSParseState *s, JSAtom name, int is_cont)
 {
     BlockEnv *top;
@@ -28932,7 +28989,7 @@ static __exception int emit_break(JSParseState *s, JSAtom name, int is_cont)
         }
         i = 0;
         if (top->has_iterator) {
-            emit_op(s, OP_iterator_close);
+            emit_iterator_close(s, top->is_async_iterator, FALSE);
             i += 3;
         }
         for(; i < top->drop_count; i++)
@@ -28992,30 +29049,7 @@ static void emit_return(JSParseState *s, BOOL hasval)
             emit_op(s, OP_nip_catch);
             /* stack: iter_obj next ret_val */
             if (top->has_iterator) {
-                if (s->cur_func->func_kind == JS_FUNC_ASYNC_GENERATOR) {
-                    int label_next, label_next2;
-                    emit_op(s, OP_nip); /* next */
-                    emit_op(s, OP_swap);
-                    emit_op(s, OP_get_field2);
-                    emit_atom(s, JS_ATOM_return);
-                    /* stack: iter_obj return_func */
-                    emit_op(s, OP_dup);
-                    emit_op(s, OP_is_undefined_or_null);
-                    label_next = emit_goto(s, OP_if_true, -1);
-                    emit_op(s, OP_call_method);
-                    emit_u16(s, 0);
-                    emit_op(s, OP_iterator_check_object);
-                    emit_op(s, OP_await);
-                    label_next2 = emit_goto(s, OP_goto, -1);
-                    emit_label(s, label_next);
-                    emit_op(s, OP_drop);
-                    emit_label(s, label_next2);
-                    emit_op(s, OP_drop);
-                } else {
-                    emit_op(s, OP_rot3r);
-                    emit_op(s, OP_undefined); /* dummy catch offset */
-                    emit_op(s, OP_iterator_close);
-                }
+                emit_iterator_close(s, top->is_async_iterator, TRUE);
             } else if (top->has_using) {
                 /* Dispose using variables. The return value is on TOS.
                    stack: ret_val */
@@ -29546,6 +29580,7 @@ static __exception int js_parse_for_in_of(JSParseState *s, int label_name,
            that a yield in the expression does not try to close a
            not-yet-created iterator */
         break_entry.has_iterator = TRUE;
+        break_entry.is_async_iterator = is_async;
         break_entry.drop_count += 2;
         if (is_async)
             emit_op(s, OP_for_await_of_start);
@@ -29626,7 +29661,7 @@ static __exception int js_parse_for_in_of(JSParseState *s, int label_name,
     emit_label(s, label_break);
     if (is_for_of) {
         /* close and drop enum_rec */
-        emit_op(s, OP_iterator_close);
+        emit_iterator_close(s, is_async, FALSE);
     } else {
         emit_op(s, OP_drop);
     }