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feat(no-trapping-shim): Ponyfill and shim for noTrapping integrity level
1 parent 215eaf4 commit 8f8d5cf

7 files changed

+286
-6
lines changed

‎packages/no-trapping-shim/package.json

-1
Original file line numberDiff line numberDiff line change
@@ -35,7 +35,6 @@
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"test:c8": "c8 $C8_OPTIONS ava --config=ava-nesm.config.js",
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"test:xs": "exit 0"
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},
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"dependencies": {},
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"devDependencies": {
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"@endo/lockdown": "workspace:^",
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"@endo/ses-ava": "workspace:^",

‎packages/no-trapping-shim/src/no-trapping-pony.js

+206
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@@ -0,0 +1,206 @@
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const OriginalObject = Object;
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const OriginalReflect = Reflect;
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const OriginalProxy = Proxy;
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const { freeze, defineProperty } = OriginalObject;
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const { apply, construct, ownKeys } = OriginalReflect;
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const noTrappingSet = new WeakSet();
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const proxyHandlerMap = new WeakMap();
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const isPrimitive = specimen => OriginalObject(specimen) !== specimen;
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/**
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* Corresponds to the internal function shared by `Object.isNoTrapping` and
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* `Reflect.isNoTrapping`.
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*
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* @param {any} specimen
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* @param {boolean} shouldThrow
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* @returns {boolean}
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*/
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const isNoTrappingInternal = (specimen, shouldThrow) => {
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if (noTrappingSet.has(specimen)) {
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return true;
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}
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if (!proxyHandlerMap.has(specimen)) {
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return false;
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}
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const [target, handler] = proxyHandlerMap.get(specimen);
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if (isNoTrappingInternal(target, shouldThrow)) {
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noTrappingSet.add(specimen);
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return true;
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}
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const trap = handler.isNoTrapping;
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if (trap === undefined) {
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return false;
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}
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const result = apply(trap, handler, [target]);
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const ofTarget = isNoTrappingInternal(target, shouldThrow);
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if (result !== ofTarget) {
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if (shouldThrow) {
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throw TypeError(
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`'isNoTrapping' proxy trap does not reflect 'isNoTrapping' of proxy target (which is '${ofTarget}')`,
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);
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}
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return false;
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}
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if (result) {
48+
noTrappingSet.add(specimen);
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}
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return result;
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};
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/**
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* Corresponds to the internal function shared by `Object.suppressTrapping` and
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* `Reflect.suppressTrapping`.
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*
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* @param {any} specimen
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* @param {boolean} shouldThrow
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* @returns {boolean}
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*/
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const suppressTrappingInternal = (specimen, shouldThrow) => {
62+
if (noTrappingSet.has(specimen)) {
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return true;
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}
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freeze(specimen);
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if (!proxyHandlerMap.has(specimen)) {
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noTrappingSet.add(specimen);
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return true;
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}
70+
const [target, handler] = proxyHandlerMap.get(specimen);
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if (isNoTrappingInternal(target, shouldThrow)) {
72+
noTrappingSet.add(specimen);
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return true;
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}
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const trap = handler.suppressTrapping;
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if (trap === undefined) {
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const result = suppressTrappingInternal(target, shouldThrow);
78+
if (result) {
79+
noTrappingSet.add(specimen);
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}
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return result;
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}
83+
const result = apply(trap, handler, [target]);
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const ofTarget = isNoTrappingInternal(target, shouldThrow);
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if (result !== ofTarget) {
86+
if (shouldThrow) {
87+
throw TypeError(
88+
`'suppressTrapping' proxy trap does not reflect 'isNoTrapping' of proxy target (which is '${ofTarget}')`,
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);
90+
}
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return false;
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}
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if (result) {
94+
noTrappingSet.add(specimen);
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}
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return result;
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};
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export const extraReflectMethods = freeze({
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isNoTrapping(target) {
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if (isPrimitive(target)) {
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throw TypeError('Reflect.isNoTrapping called on non-object');
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}
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return isNoTrappingInternal(target, false);
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},
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suppressTrapping(target) {
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if (isPrimitive(target)) {
108+
throw TypeError('Reflect.suppressTrapping called on non-object');
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}
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return suppressTrappingInternal(target, false);
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},
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});
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export const extraObjectMethods = freeze({
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isNoTrapping(target) {
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if (isPrimitive(target)) {
117+
return true;
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}
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return isNoTrappingInternal(target, true);
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},
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suppressTrapping(target) {
122+
if (isPrimitive(target)) {
123+
return target;
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}
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if (suppressTrappingInternal(target, true)) {
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return target;
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}
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throw TypeError('preventExtensions trap returned falsy');
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},
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});
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const addExtras = (base, ...extrasArgs) => {
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for (const extras of extrasArgs) {
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for (const key of ownKeys(extras)) {
135+
if (base[key] !== extras[key]) {
136+
defineProperty(base, key, {
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value: extras[key],
138+
writable: true,
139+
enumerable: false,
140+
configurable: true,
141+
});
142+
}
143+
}
144+
}
145+
};
146+
147+
const ReflectPlus = {};
148+
addExtras(ReflectPlus, OriginalReflect, extraReflectMethods);
149+
export { ReflectPlus };
150+
151+
const ObjectPlus = function Object(...args) {
152+
if (new.target) {
153+
return construct(OriginalObject, args, new.target);
154+
} else {
155+
return apply(OriginalObject, this, args);
156+
}
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};
158+
ObjectPlus.prototype = OriginalObject.prototype;
159+
addExtras(ObjectPlus, OriginalObject, extraObjectMethods);
160+
export { ObjectPlus };
161+
162+
const makeMetaHandler = handler =>
163+
freeze({
164+
get(_, trapName, _receiver) {
165+
return freeze((target, ...rest) => {
166+
if (
167+
isNoTrappingInternal(target, true) ||
168+
handler[trapName] === undefined
169+
) {
170+
return ReflectPlus[trapName](target, ...rest);
171+
} else {
172+
return handler[trapName](target, ...rest);
173+
}
174+
});
175+
},
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});
177+
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const makeSafeHandler = handler =>
179+
new OriginalProxy({}, makeMetaHandler(handler));
180+
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/**
182+
* In the shim, `ProxyPlus` should replace the global `Proxy`.
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*
184+
* @param {any} target
185+
* @param {object} handler
186+
*/
187+
const ProxyPlus = function Proxy(target, handler) {
188+
if (new.target !== ProxyPlus) {
189+
if (new.target === undefined) {
190+
throw TypeError('Proxy constructor requires "new"');
191+
}
192+
throw TypeError('Safe Proxy shim does not support subclassing');
193+
}
194+
const safeHandler = makeSafeHandler(handler);
195+
const proxy = new OriginalProxy(target, safeHandler);
196+
proxyHandlerMap.set(proxy, [target, handler]);
197+
return proxy;
198+
};
199+
ProxyPlus.revocable = (target, handler) => {
200+
const safeHandler = makeSafeHandler(handler);
201+
const { proxy, revoke } = OriginalProxy.revocable(target, safeHandler);
202+
proxyHandlerMap.set(proxy, [target, handler]);
203+
return { proxy, revoke };
204+
};
205+
206+
export { ProxyPlus };

‎packages/no-trapping-shim/src/no-trapping-shim.js

+12
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@@ -0,0 +1,12 @@
1+
/* global globalThis */
2+
import { ReflectPlus, ObjectPlus, ProxyPlus } from './no-trapping-pony.js';
3+
4+
globalThis.Reflect = ReflectPlus;
5+
6+
// @ts-expect-error Something about the type of the Object constructor
7+
globalThis.Object = ObjectPlus;
8+
// eslint-disable-next-line no-extend-native
9+
Object.prototype.constructor = ObjectPlus;
10+
11+
// @ts-expect-error Something about the type of Proxy
12+
globalThis.Proxy = ProxyPlus;

‎packages/no-trapping-shim/test/index.test.js

-5
This file was deleted.

‎packages/no-trapping-shim/test/no-trapping-pony.test.js

+26
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@@ -0,0 +1,26 @@
1+
import test from '@endo/ses-ava/prepare-endo.js';
2+
import { ReflectPlus, ProxyPlus } from '../src/no-trapping-pony.js';
3+
4+
const { freeze, isFrozen } = Object;
5+
6+
test('no-trapping-pony', async t => {
7+
const specimen = { foo: 8 };
8+
9+
const sillyHandler = freeze({
10+
get(target, prop, receiver) {
11+
return [target, prop, receiver];
12+
},
13+
});
14+
15+
const safeProxy = new ProxyPlus(specimen, sillyHandler);
16+
17+
t.false(ReflectPlus.isNoTrapping(specimen));
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t.false(isFrozen(specimen));
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t.deepEqual(safeProxy.foo, [specimen, 'foo', safeProxy]);
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t.true(ReflectPlus.suppressTrapping(specimen));
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t.true(ReflectPlus.isNoTrapping(specimen));
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t.true(isFrozen(specimen));
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t.deepEqual(safeProxy.foo, 8);
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});

‎packages/no-trapping-shim/test/no-trapping-shim.test.js

+29
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@@ -0,0 +1,29 @@
1+
import '../src/no-trapping-shim.js';
2+
// TODO make compat with ses and uncomment
3+
// import test from '@endo/ses-ava/prepare-endo.js';
4+
// instead of
5+
import test from 'ava';
6+
7+
const { freeze, isFrozen } = Object;
8+
9+
test('no-trapping-pony', async t => {
10+
const specimen = { foo: 8 };
11+
12+
const sillyHandler = freeze({
13+
get(target, prop, receiver) {
14+
return [target, prop, receiver];
15+
},
16+
});
17+
18+
const safeProxy = new Proxy(specimen, sillyHandler);
19+
20+
t.false(Reflect.isNoTrapping(specimen));
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t.false(isFrozen(specimen));
22+
t.deepEqual(safeProxy.foo, [specimen, 'foo', safeProxy]);
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24+
t.true(Reflect.suppressTrapping(specimen));
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t.true(Reflect.isNoTrapping(specimen));
27+
t.true(isFrozen(specimen));
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t.deepEqual(safeProxy.foo, 8);
29+
});

‎yarn.lock

+13
Original file line numberDiff line numberDiff line change
@@ -702,6 +702,19 @@ __metadata:
702702
languageName: unknown
703703
linkType: soft
704704

705+
"@endo/no-trapping-shim@workspace:packages/no-trapping-shim":
706+
version: 0.0.0-use.local
707+
resolution: "@endo/no-trapping-shim@workspace:packages/no-trapping-shim"
708+
dependencies:
709+
"@endo/lockdown": "workspace:^"
710+
"@endo/ses-ava": "workspace:^"
711+
ava: "npm:^6.1.3"
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c8: "npm:^7.14.0"
713+
tsd: "npm:^0.31.2"
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typescript: "npm:~5.6.3"
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languageName: unknown
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linkType: soft
717+
705718
"@endo/pass-style@workspace:^, @endo/pass-style@workspace:packages/pass-style":
706719
version: 0.0.0-use.local
707720
resolution: "@endo/pass-style@workspace:packages/pass-style"

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