kingmph at gmail.com (2018-01-16T15:35:34.202Z)
---------- Forwarded message ---------- From: Ranando King <kingmph at gmail.com> Date: Sat, Jan 13, 2018 at 2:32 PM Subject: Re: An idea to extend the functionality of Proxy objects. To: Isiah Meadows <isiahmeadows at gmail.com> After thinking about it a bit more, maybe you mean something like this: Original: **[[SetPrototypeOf]] (V)** - The Type of the return value must be Boolean. - If target is non-extensible, [[SetPrototypeOf]] must return false, unless V is the [SameValue](https://tc39.github.io/ecma262/#sec-samevalue) as the target's observed [[GetPrototypeOf]] value. Modified: **[[SetPrototypeOf]] (V)** - The Type of the return value must be Boolean. - *If [[IsExtensible]] returns false*, [[SetPrototypeOf]] must return false, unless V is the [SameValue](https://tc39.github.io/ecma262/#sec-samevalue) as *that returned by [[GetPrototypeOf]]*.
kingmph at gmail.com (2018-01-16T15:34:27.108Z)
---------- Forwarded message ---------- From: Ranando King <kingmph at gmail.com> Date: Sat, Jan 13, 2018 at 2:32 PM Subject: Re: An idea to extend the functionality of Proxy objects. To: Isiah Meadows <isiahmeadows at gmail.com> After thinking about it a bit more, maybe you mean something like this: Original: **[[SetPrototypeOf]] (V)** - The Type of the return value must be Boolean. - If target is non-extensible, [[SetPrototypeOf]] must return false, unless V is the [SameValue](https://tc39.github.io/ecma262/#sec-samevalue) as the target's observed [[GetPrototypeOf]] value. Modified: **[[SetPrototypeOf]] (V)** - The Type of the return value must be Boolean. - *If [[IsExtensible]] returns false*, [[SetPrototypeOf]] must return false, unless V is the [SameValue](https://tc39.github.io/ecma262/#sec-samevalue) as *that returned by [[GetPrototypeOf]]*.
---------- Forwarded message ---------- From: Ranando King <kingmph at gmail.com> Date: Sat, Jan 13, 2018 at 2:32 PM Subject: Re: An idea to extend the functionality of Proxy objects. To: Isiah Meadows <isiahmeadows at gmail.com> After thinking about it a bit more, maybe you mean something like this: [[SetPrototypeOf]] (V) - The Type of the return value must be Boolean. - If target is non-extensible, [[SetPrototypeOf]] must return false, unless V is the SameValue <https://tc39.github.io/ecma262/#sec-samevalue> as the target's observed [[GetPrototypeOf]] value. After thinking about it a bit more, maybe you mean something like this: [[SetPrototypeOf]] (V) - The Type of the return value must be Boolean. - *If [[IsExtensible]] returns false*, [[SetPrototypeOf]] must return false, unless V is the SameValue <https://tc39.github.io/ecma262/#sec-samevalue> as *that returned by [[GetPrototypeOf]]*. After thinking about it a bit more, maybe you mean something like this: On Sat, Jan 13, 2018 at 2:23 PM, Ranando King <kingmph at gmail.com> wrote: > While I understand what you're getting at, The invariants would *not* change > under my idea. In fact, I've thought about it carefully and crafted the > wording change from my suggestion specifically so that the invariants > wouldn't change. My goal is simply to change this process: > > some action on proxied target -> > [[ProxyHandler]] method called -> > [[ProxyHandler]] method results checked by testing against > Reflect.<methods>(target...) -> > error on failure -> return result > > into > > some action on proxied target -> > [[ProxyHandler]] method called -> > [[ProxyHandler]] method results checked by testing against > [[ProxyHandler]].<methods>(target...) -> > error on failure -> return result > > so that the developers proxy handler implementation is solely responsible > for ensuring that the invariant requirements are maintained. The <methods> > in question are exactly those described by the invariants. The only thing > that is changing is that [[ProxyHandler]] would be the authority for the > information used to ensure that the invariants have not been violated. > > The gist is that while currently, given a caller, a proxy, and a target, > the target constrains what the caller can do with the proxy, what I want is > to reverse it so that the proxy constrains what the caller can do with the > target, and all still without violating the existing invariant > requirements. Does that make what I'm after a little clearer? > > On Fri, Jan 12, 2018 at 9:07 PM, Isiah Meadows <isiahmeadows at gmail.com> > wrote: > >> Not full, but changes of some kind will likely be required, and you >> should address and document how those would be changed. >> >> On Fri, Jan 12, 2018, 20:41 Ranando King <kingmph at gmail.com> wrote: >> > >> > You're right about the mistake with Object.seal. I wasn't too focused >> on that part when writing the example code. So are you suggesting that I >> also prepare a fully detailed rewrite of the invariant rules for comparison? >> > >> > On Fri, Jan 12, 2018 at 6:44 PM, Isiah Meadows <isiahmeadows at gmail.com> >> wrote: >> >> >> >> Make sure to compare your changes to the [invariants of the essential >> >> internal methods][1], since changes to them would require some >> >> *significant* justification. And yes, your proposal would require >> >> changes to them. (I'm not a TC39 member, but I've read up enough about >> >> their decisions to make some educated guesses, and core changes tend >> >> to be met with extreme skepticism.) >> >> >> >> Also, note that you probably meant to, in `SourceFile.js`, use >> >> `Object.seal(obj)`, not `obj.seal()` (it's a static method, not an >> >> instance method). >> >> >> >> [1]: https://tc39.github.io/ecma262/#sec-invariants-of-the-essent >> ial-internal-methods >> >> ----- >> >> >> >> Isiah Meadows >> >> me at isiahmeadows.com >> >> >> >> Looking for web consulting? Or a new website? >> >> Send me an email and we can get started. >> >> www.isiahmeadows.com >> >> >> >> >> >> On Fri, Jan 12, 2018 at 5:38 PM, Ranando King <kingmph at gmail.com> >> wrote: >> >> > I have an idea I’d like to propose with regards to Proxy objects. I >> would >> >> > like to make a change to spec section 6.1.7.3 (as seen in the latest >> draft). >> >> > The change is as follows: >> >> > >> >> > The Internal Methods of Objects of an ECMAScript engine must conform >> to the >> >> > list of invariants specified below. Ordinary ECMAScript Objects as >> well as >> >> > all standard exotic objects in this specification maintain these >> invariants. >> >> > ECMAScript Proxy objects maintain these invariants by means of >> runtime >> >> > checks on the result of traps invoked on the [[ProxyHandler]] object >> using >> >> > either the corresponding traps on the [[ProxyHandler]] should the >> needed >> >> > trap be defined, or the default internal method otherwise. >> >> > >> >> > Put simply, the change that I’m requesting would have the runtime >> checks >> >> > verify the selfconsistency of the results returned by the >> [[ProxyHandler]] >> >> > object instead of testing the [[ProxyHandler]] results against the >> target. >> >> > The rationale behind this change is to allow Proxy objects the >> freedom to >> >> > behave in a manner that is inconsistent with the behavior that would >> have >> >> > been should the target have been accessed directly, while still >> requiring >> >> > that the consistency of the behavior of the essential internal >> methods be >> >> > upheld. In this way, a Proxy object would be able to project new >> properties >> >> > for a proxied target even if the target object is not extensible, or >> even >> >> > completely hide non-configurable properties. The requirement to do >> so would >> >> > be implementation of the appropriate [[ProxyHandler]] methods so as >> to >> >> > satisfy all of the corresponding invariants for all implemented >> handlers. >> >> > The ECMAScript engine would then see results consistent with >> expectations, >> >> > despite the fact that the results are inconsistent with the actual >> nature of >> >> > the proxied target object. >> >> > >> >> > An example might be the case of a library to mock objects. >> >> > >> >> > /* SourceFile.js */ >> >> > var obj = { bar: "The real bar. Accept no imitations!", fubar: >> "Always has >> >> > been." }; >> >> > obj.seal(); >> >> > >> >> > export default obj; >> >> > >> >> > /* TestFile.js */ >> >> > import testObj from "SourceFile"; >> >> > >> >> > var mock = new Proxy(testObj, { >> >> > has: function(target, key) { >> >> > var retval = false; >> >> > if (key == "foo") { //add the foo property >> >> > retval = true; >> >> > } >> >> > else if (key != "bar") { //hide the bar property >> >> > retval = (key in target); >> >> > } >> >> > >> >> > return retval; >> >> > }, >> >> > ownKeys: function(target) { >> >> > var retval = Reflect.ownKeys(target); >> >> > var barIndex = retval.indexOf(bar); >> >> > >> >> > if (barIndex != -1) >> >> > retval.splice(barIndex, 1); >> >> > >> >> > retval.push("foo"); >> >> > return retval; >> >> > }, >> >> > defineProperty: function(target, key, descriptor) { >> >> > var retval = true; >> >> > if ((key == "foo") || (key == "bar")) { >> >> > retval = false; >> >> > } >> >> > else { >> >> > Reflect.defineProperty(target, key, descriptor); >> >> > } >> >> > >> >> > return retval; >> >> > }, >> >> > get: function(target, key) { >> >> > var retval = undefined; >> >> > >> >> > if (key == "foo") { >> >> > retval = "You got the fake property!" >> >> > } >> >> > else if (key != "bar") { >> >> > retval = Reflect.deleteProperty(target, key); >> >> > } >> >> > >> >> > return retval; >> >> > }, >> >> > set: function(target, key, value) { >> >> > var retval = false; >> >> > if ((key != "foo") && (key != "bar")) >> >> > retval = Reflect.set(target, key); >> >> > } >> >> > return retval; >> >> > }, >> >> > deleteProperty: function(target, key) { >> >> > var retval = false; >> >> > if ((key != "foo") && (key != "bar")) >> >> > retval = Reflect.deleteProperty(target, key); >> >> > } >> >> > return retval; >> >> > }, >> >> > getOwnPropertyDescriptor: function(target, key) { >> >> > var retval; >> >> > if (key == "foo") { >> >> > retval = { >> >> > enumerable: true, >> >> > writable: false, >> >> > configurable: false, >> >> > value: "You got the fake property!" >> >> > }; >> >> > } >> >> > else if (key != "bar") { >> >> > retval = Reflect.getOwnPropertyDescriptor(target, key); >> >> > } >> >> > return retval; >> >> > } >> >> > }); >> >> > >> >> > console.log(mock.fubar); // "Always has been" >> >> > console.log(mock.foo); // #1 >> >> > console.log(mock.bar); // #2 >> >> > >> >> > >> >> > Currently, if the above code were run, an error would be thrown at >> comment >> >> > #1. Even if that line was commented out, an error would be thrown at >> comment >> >> > #2. With my proposed change, the code would run successfully. >> Comment #1 >> >> > would be "You got the fake property!" and comment #2 would be >> undefined. As >> >> > a matter of completeness, if the handler only contained the "get" >> and "set" >> >> > methods, this code would throw an error just as it currently would. >> The >> >> > reason that it works with all of the handlers this that these >> handlers >> >> > ensure that a consistent description of the is being presented to the >> >> > interpreter since the interpreter would rely on the methods of the >> proxy >> >> > object's handler to supply the data needed to validate the response >> of the >> >> > original call. >> >> > >> >> > _______________________________________________ >> >> > es-discuss mailing list >> >> > es-discuss at mozilla.org >> >> > https://mail.mozilla.org/listinfo/es-discuss >> >> > >> > >> > >> > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20180115/6481f9da/attachment-0001.html>