Allow Proxy target and handler to be Proxy too

RELEASES.rst

@@ -3396,6 +3396,11 @@ Planned
 2.4.0 (XXXX-XX-XX)
 ------------------
 
+* Allow a Proxy object to have a Proxy as its target (i.e. Proxy chains)
+  (GH-1947)
+
+* Allow a Proxy handler object to be a Proxy (GH-1947)
+
 3.0.0 (XXXX-XX-XX)
 ------------------
 

src-input/duk_api_stack.c

@@ -5558,19 +5558,11 @@ DUK_EXTERNAL duk_idx_t duk_push_proxy(duk_hthread *thr, duk_uint_t proxy_flags)
 	DUK__CHECK_SPACE();
 #endif
 
-	/* Reject a proxy object as the target because it would need
-	 * special handling in property lookups.  (ES2015 has no such
-	 * restriction.)
-	 */
+	/* Proxy target validation. */
 	h_target = duk_require_hobject_promote_mask(thr, -2, DUK_TYPE_MASK_LIGHTFUNC | DUK_TYPE_MASK_BUFFER);
 	DUK_ASSERT(h_target != NULL);
-	if (DUK_HOBJECT_IS_PROXY(h_target)) {
-		goto fail_args;
-	}
 
-	/* Reject a proxy object as the handler because it would cause
-	 * potentially unbounded recursion.  (ES2015 has no such
-	 * restriction.)
+	/* Proxy handler object validation.
 	 *
 	 * There's little practical reason to use a lightfunc or a plain
 	 * buffer as the handler table: one could only provide traps via
@@ -5580,9 +5572,6 @@ DUK_EXTERNAL duk_idx_t duk_push_proxy(duk_hthread *thr, duk_uint_t proxy_flags)
 	 */
 	h_handler = duk_require_hobject_promote_mask(thr, -1, DUK_TYPE_MASK_LIGHTFUNC | DUK_TYPE_MASK_BUFFER);
 	DUK_ASSERT(h_handler != NULL);
-	if (DUK_HOBJECT_IS_PROXY(h_handler)) {
-		goto fail_args;
-	}
 
 	/* XXX: Proxy object currently has no prototype, so ToPrimitive()
 	 * coercion fails which is a bit confusing.
@@ -5629,10 +5618,6 @@ DUK_EXTERNAL duk_idx_t duk_push_proxy(duk_hthread *thr, duk_uint_t proxy_flags)
 	DUK_DD(DUK_DDPRINT("created Proxy: %!iT", duk_get_tval(thr, -1)));
 
 	return (duk_idx_t) (thr->valstack_top - thr->valstack_bottom - 1);
-
- fail_args:
-	DUK_ERROR_TYPE_INVALID_ARGS(thr);
-	DUK_WO_NORETURN(return 0;);
 }
 #else  /* DUK_USE_ES6_PROXY */
 DUK_EXTERNAL duk_idx_t duk_push_proxy(duk_hthread *thr, duk_uint_t proxy_flags) {

src-input/duk_bi_object.c

@@ -687,6 +687,8 @@ DUK_INTERNAL duk_ret_t duk_bi_object_constructor_keys_shared(duk_hthread *thr) {
 	DUK_ASSERT(magic >= 0 && magic < (duk_int_t) (sizeof(duk__object_keys_enum_flags) / sizeof(duk_small_uint_t)));
 	enum_flags = duk__object_keys_enum_flags[magic];
 
+	/* FIXME: Proxy as target? */
+
 	duk_proxy_ownkeys_postprocess(thr, h_proxy_target, enum_flags);
 	return 1;
 

src-input/duk_hobject_enum.c

@@ -254,6 +254,8 @@ DUK_INTERNAL void duk_hobject_enumerator_create(duk_hthread *thr, duk_small_uint
 		DUK_DDD(DUK_DDDPRINT("h_proxy_target=%!O", (duk_heaphdr *) h_proxy_target));
 		enum_target = h_proxy_target;
 
+		/* FIXME: recursive proxy case? */
+
 		duk_push_hobject(thr, enum_target);  /* -> [ ... enum_target res handler undefined target ] */
 		duk_put_prop_stridx_short(thr, -4, DUK_STRIDX_INT_TARGET);
 

src-input/duk_hobject_props.c

@@ -456,7 +456,11 @@ DUK_LOCAL duk_bool_t duk__proxy_check_prop(duk_hthread *thr, duk_hobject *obj, d
 	 * are not realized now.)
 	 */
 
-	/* XXX: C recursion limit if proxies are allowed as handler/target values */
+	/* FIXME: C recursion limit if proxies are allowed as handler/target values?
+	 * Or rely on later stack depth macro check (insert one here)?
+	 */
+
+	/* FIXME: implement recursive Proxy target support directly here? */
 
 	duk_require_stack(thr, DUK__VALSTACK_PROXY_LOOKUP);
 	duk_push_hobject(thr, h_handler);
@@ -2372,6 +2376,7 @@ DUK_INTERNAL duk_bool_t duk_hobject_getprop(duk_hthread *thr, duk_tval *tv_obj,
 	 *  Coercion and fast path processing
 	 */
 
+ recheck_object:
 	switch (DUK_TVAL_GET_TAG(tv_obj)) {
 	case DUK_TAG_UNDEFINED:
 	case DUK_TAG_NULL: {
@@ -2552,6 +2557,7 @@ DUK_INTERNAL duk_bool_t duk_hobject_getprop(duk_hthread *thr, duk_tval *tv_obj,
 
 			curr = h_target;  /* resume lookup from target */
 			DUK_TVAL_SET_OBJECT(tv_obj, curr);
+			goto recheck_object;
 		}
 #endif  /* DUK_USE_ES6_PROXY */
 
@@ -2891,6 +2897,7 @@ DUK_INTERNAL duk_bool_t duk_hobject_hasprop(duk_hthread *thr, duk_tval *tv_obj,
 	DUK_ASSERT(obj != NULL);
 	DUK_UNREF(arr_idx);
 
+ recheck_object:
 #if defined(DUK_USE_ES6_PROXY)
 	if (DUK_UNLIKELY(DUK_HOBJECT_IS_PROXY(obj))) {
 		duk_hobject *h_target;
@@ -2936,6 +2943,7 @@ DUK_INTERNAL duk_bool_t duk_hobject_hasprop(duk_hthread *thr, duk_tval *tv_obj,
 		}
 
 		obj = h_target;  /* resume check from proxy target */
+		goto recheck_object;
 	}
 #endif  /* DUK_USE_ES6_PROXY */
 
@@ -3378,6 +3386,7 @@ DUK_INTERNAL duk_bool_t duk_hobject_putprop(duk_hthread *thr, duk_tval *tv_obj,
 	 *  Coercion and fast path processing.
 	 */
 
+ recheck_object:
 	switch (DUK_TVAL_GET_TAG(tv_obj)) {
 	case DUK_TAG_UNDEFINED:
 	case DUK_TAG_NULL: {
@@ -3539,6 +3548,7 @@ DUK_INTERNAL duk_bool_t duk_hobject_putprop(duk_hthread *thr, duk_tval *tv_obj,
 
 			orig = h_target;  /* resume write to target */
 			DUK_TVAL_SET_OBJECT(tv_obj, orig);
+			goto recheck_object;
 		}
 #endif  /* DUK_USE_ES6_PROXY */
 
@@ -4451,6 +4461,7 @@ DUK_INTERNAL duk_bool_t duk_hobject_delprop(duk_hthread *thr, duk_tval *tv_obj,
 	duk_push_tval(thr, tv_obj);
 	duk_push_tval(thr, tv_key);
 
+ recheck_object:
 	tv_obj = DUK_GET_TVAL_NEGIDX(thr, -2);
 	if (DUK_TVAL_IS_OBJECT(tv_obj)) {
 		duk_hobject *obj = DUK_TVAL_GET_OBJECT(tv_obj);
@@ -4501,7 +4512,9 @@ DUK_INTERNAL duk_bool_t duk_hobject_delprop(duk_hthread *thr, duk_tval *tv_obj,
 				goto done_rc;
 			}
 
-			obj = h_target;  /* resume delete to target */
+			duk_push_hobject(thr, h_target);  /* resume delete to target */
+			duk_replace(thr, -3);
+			goto recheck_object;
 		}
 #endif  /* DUK_USE_ES6_PROXY */
 

src-input/duk_js_ops.c

@@ -1158,9 +1158,10 @@ DUK_LOCAL duk_bool_t duk__js_instanceof_helper(duk_hthread *thr, duk_tval *tv_x,
 		if (!val) {
 			goto pop3_and_false;
 		}
-
 		DUK_ASSERT(val != NULL);
+
 #if defined(DUK_USE_ES6_PROXY)
+		/* FIXME: getPrototypeOf trap; testcase; comment */
 		val = duk_hobject_resolve_proxy_target(val);
 #endif
 

tests/ecmascript/test-bi-proxy-handler-proxy-1.js

@@ -0,0 +1,28 @@
+/*===
+P1.get called true get true
+get called true foo true
+<<<foo>>>
+P1.get called true get true
+get called true bar true
+<<<bar>>>
+===*/
+
+var T1 = {};
+var P1 = new Proxy(T1, {
+    get: function (targ, prop, recv) {
+        print('P1.get called', targ === T1, prop, recv === P1);
+
+        if (prop === 'get') {
+            return function (targ, prop, recv) {
+                print('get called', targ === T2, prop, recv === P2);
+                return '<<<' + prop + '>>>'
+            };
+        }
+    }
+});
+
+var T2 = {};
+var P2 = new Proxy(T2, P1);
+
+print(P2.foo);
+print(P2.bar);

tests/ecmascript/test-bi-proxy-handler-proxy-2.js

@@ -0,0 +1,17 @@
+/*===
+P1.get called foo
+aiee
+===*/
+
+var curr = {
+    get: function (targ, prop, recv) {
+        print('P1.get called', prop);
+        return 'aiee';
+    }
+};
+for (var i = 0; i < 1e6; i++) {
+    curr = new Proxy(curr, {});
+}
+
+var finalProxy = new Proxy({}, curr);
+print(finalProxy.foo);

tests/ecmascript/test-bi-proxy-target-proxy-1.js

@@ -0,0 +1,25 @@
+/*===
+bar
+undefined
+true
+false
+123
+true
+undefined
+true
+===*/
+
+var A = { foo: 'bar' };
+var P1 = new Proxy(A, {});
+var P2 = new Proxy(P1, {});
+var P3 = new Proxy(P2, {});
+
+print(P3.foo);
+print(P3.bar);
+print('foo' in P3);
+print('bar' in P3);
+P3.quux = 123;
+print(A.quux);
+print(delete P3.quux);
+print(A.quux);
+print(delete P3.noSuch);

tests/ecmascript/test-bi-proxy-target-proxy-2.js

@@ -0,0 +1,11 @@
+/*===
+123
+===*/
+
+var curr = { foo: 123 };
+for (var i = 0; i < 1e6; i++) {
+    curr = new Proxy(curr, {});
+}
+
+var finalProxy = curr;
+print(finalProxy.foo);