Fix AsyncGenerator.prototype.return error handling (#109)

A poisoned .constructor property is observable and the resulting
exception should be delivered to the catch handler, not silently
dropped, otherwise the generator hangs.

Author: bnoordhuis

quickjs.c

@@ -17407,10 +17407,19 @@ static int js_async_generator_completed_return(JSContext *ctx,
     JSValue promise, resolving_funcs[2], resolving_funcs1[2];
     int res;
 
-    promise = js_promise_resolve(ctx, ctx->promise_ctor,
-                                 1, (JSValueConst *)&value, 0);
-    if (JS_IsException(promise))
-        return -1;
+    // Can fail looking up JS_ATOM_constructor when is_reject==0.
+    promise = js_promise_resolve(ctx, ctx->promise_ctor, 1, &value,
+                                 /*is_reject*/0);
+    // A poisoned .constructor property is observable and the resulting
+    // exception should be delivered to the catch handler.
+    if (JS_IsException(promise)) {
+        JSValue err = JS_GetException(ctx);
+        promise = js_promise_resolve(ctx, ctx->promise_ctor, 1, &err,
+                                     /*is_reject*/1);
+        JS_FreeValue(ctx, err);
+        if (JS_IsException(promise))
+            return -1;
+    }
     if (js_async_generator_resolve_function_create(ctx,
                                                    JS_MKPTR(JS_TAG_OBJECT, s->generator),
                                                    resolving_funcs1,

test262_errors.txt

@@ -1,8 +1,4 @@
 test262/test/annexB/language/eval-code/direct/script-decl-lex-collision-in-sloppy-mode.js:13: Test262Error: Expected a SyntaxError to be thrown but no exception was thrown at all
-test262/test/built-ins/AsyncGeneratorPrototype/return/return-state-completed-broken-promise.js:53: TypeError: $DONE() not called
-test262/test/built-ins/AsyncGeneratorPrototype/return/return-state-completed-broken-promise.js:53: strict mode: TypeError: $DONE() not called
-test262/test/built-ins/AsyncGeneratorPrototype/return/return-suspendedStart-broken-promise.js:34: TypeError: $DONE() not called
-test262/test/built-ins/AsyncGeneratorPrototype/return/return-suspendedStart-broken-promise.js:34: strict mode: TypeError: $DONE() not called
 test262/test/built-ins/AsyncGeneratorPrototype/return/return-suspendedYield-broken-promise-try-catch.js:39: TypeError: $DONE() not called
 test262/test/built-ins/AsyncGeneratorPrototype/return/return-suspendedYield-broken-promise-try-catch.js:39: strict mode: TypeError: $DONE() not called
 test262/test/built-ins/RegExp/lookahead-quantifier-match-groups.js:27: Test262Error: Expected [a, abc] and [a, undefined] to have the same contents. ? quantifier