Isn't this just a different version of the private names idea that Kevin & Daniel were pushing before settling into "proposal-class-fields"? If not, then what's the difference?
On Mon, Jul 30, 2018 at 6:01 AM Michael Theriot < michael.lee.ther...@gmail.com> wrote: > I'll just say it feels inconsistent with how every other property is > configured. That the key itself holds magic behavior-changing information. > It's not a use case or overhead concern. > > On Monday, July 30, 2018, Isiah Meadows <isiahmead...@gmail.com> wrote: > >> Um, no. The use case is *extremely* limited, and that ruins a few >> optimizations you could otherwise make with private symbols (like >> caching proxy forwarding without having to bail out). >> >> Besides, whether a symbol is private requires exactly one bit to >> store, so there's no real overhead with storing it on the object. >> Heck, if you want to optimize it better, you might choose to store >> that same bit on both the symbol and the object descriptor itself, and >> I'd expect engines to do just that - it saves a pointer dereference. >> ----- >> >> Isiah Meadows >> m...@isiahmeadows.com >> www.isiahmeadows.com >> >> >> On Mon, Jul 30, 2018 at 1:25 AM, Michael Theriot >> <michael.lee.ther...@gmail.com> wrote: >> > Also throwing this out there, symbols would now carry additional >> > information: private or normal. Would it be better to configure this on >> > objects instead? >> > >> > E.g. `Object.setPropertySymbolVisibility(object, symbol, true / false)` >> > >> > (and then ideally sugar for this) >> > >> > That way a symbol's visibility on an object is information held on the >> > object rather than the primitive. A little more work involved, but >> lines up >> > with Object.defineProperty and symbols remain purely unique identifiers. >> > >> > On Monday, July 30, 2018, Isiah Meadows <isiahmead...@gmail.com> wrote: >> >> >> >> I'm aware it's possible to misuse, but if concerns of misuse were a >> >> serious issue, we wouldn't have iterators, for example [1] [2]. But >> >> IMHO freeing weak maps from a role they weren't designed for >> >> substantially outweighs the risks of abusing them further (and the >> >> abuses are incredibly frequent). >> >> >> >> [1]: >> >> >> https://esdiscuss.org/topic/iterators-generators-finally-and-scarce-resources-was-april-10-2014-meeting-notes >> >> [2]: https://esdiscuss.org/topic/resource-management >> >> >> >> ----- >> >> >> >> Isiah Meadows >> >> m...@isiahmeadows.com >> >> www.isiahmeadows.com >> >> >> >> >> >> On Sun, Jul 29, 2018 at 10:55 PM, Michael Theriot >> >> <michael.lee.ther...@gmail.com> wrote: >> >> > Right, I wouldn't, but I'm concerned others would misuse it. I don't >> >> > think >> >> > it's a blocker though, and actually frees weakmaps from trying to >> fill >> >> > this >> >> > role. >> >> > >> >> > >> >> > On Sunday, July 29, 2018, Isiah Meadows <isiahmead...@gmail.com> >> wrote: >> >> >> >> >> >> It will, but weak maps will still remain useful for cases when >> you're >> >> >> semantically dealing with a key/value map. In theory, you could >> >> >> implement a weak map on top of this [1], but in practice, it doesn't >> >> >> always make sense to do it. A good example of this is if you are >> >> >> "tagging" an object with data. If this data isn't really part of the >> >> >> object itself, you shouldn't be using a private symbol for it. >> Another >> >> >> good example is if you're doing simple caching and you need to clear >> >> >> the weak map by replacing it. Using private symbols for this doesn't >> >> >> really fit with the domain here, so you're more likely just to >> confuse >> >> >> future readers (including yourself) if you do this. >> >> >> >> >> >> [1]: >> >> >> >> https://gist.github.com/isiahmeadows/a8494868c4b193dfbf7139589f472ad8 >> >> >> ----- >> >> >> >> >> >> Isiah Meadows >> >> >> m...@isiahmeadows.com >> >> >> www.isiahmeadows.com >> >> >> >> >> >> >> >> >> On Sun, Jul 29, 2018 at 10:05 PM, Michael Theriot >> >> >> <michael.lee.ther...@gmail.com> wrote: >> >> >> > Private symbols sounds like an easy win. They would be painfully >> >> >> > simple, >> >> >> > real properties, not just variables with property imitation syntax >> >> >> > that >> >> >> > undoubtedly confuses people. With the added benefit that children >> can >> >> >> > truly >> >> >> > override the base class, freedom to define private members shared >> >> >> > across >> >> >> > otherwise unrelated objects, and even injection. My only concern >> is >> >> >> > that >> >> >> > it >> >> >> > could cross into WeakMap use cases. >> >> >> > >> >> >> > >> >> >> > On Sunday, July 29, 2018, Isiah Meadows <isiahmead...@gmail.com> >> >> >> > wrote: >> >> >> >> >> >> >> >> BTW, I came up with an alternate proposal for privacy altogether: >> >> >> >> https://github.com/tc39/proposal-class-fields/issues/115 >> >> >> >> >> >> >> >> TL;DR: private symbols that proxies can't see and that can't be >> >> >> >> enumerated. >> >> >> >> ----- >> >> >> >> >> >> >> >> Isiah Meadows >> >> >> >> m...@isiahmeadows.com >> >> >> >> www.isiahmeadows.com >> >> >> >> >> >> >> >> >> >> >> >> On Sun, Jul 29, 2018 at 12:23 AM, Darien Valentine >> >> >> >> <valentin...@gmail.com> wrote: >> >> >> >> >> What you're essentially asking for is a violatable private >> field, >> >> >> >> >> or >> >> >> >> >> as >> >> >> >> >> has been described by others, a "soft private". >> >> >> >> > >> >> >> >> > We might have different definitions here, but I would describe >> >> >> >> > what >> >> >> >> > I’m >> >> >> >> > talking about as hard private. Soft private, at least as it >> >> >> >> > appears >> >> >> >> > to >> >> >> >> > have >> >> >> >> > been defined in [prior >> >> >> >> > >> >> >> >> > >> >> >> >> > discussions]( >> https://github.com/tc39/proposal-private-fields/issues/33), >> >> >> >> > described an avenue where symbol keyed properties were given a >> new >> >> >> >> > syntactic >> >> >> >> > form — but they were still just regular symbol keys, and >> therefore >> >> >> >> > could >> >> >> >> > be >> >> >> >> > introspected by outside agents who had not been given express >> >> >> >> > privilege >> >> >> >> > to >> >> >> >> > do so: >> >> >> >> > >> >> >> >> >> [...] the core would be that "private state" is simply >> (public) >> >> >> >> >> symbol-named properties, with syntactic sugar for those >> symbols, >> >> >> >> >> and >> >> >> >> >> possibly some kind of introspection over them [...] >> >> >> >> > >> >> >> >> > The thread goes on to contrast the soft model with an earlier >> >> >> >> > version >> >> >> >> > of >> >> >> >> > the >> >> >> >> > private fields proposal seen today. The hard private example >> uses >> >> >> >> > the >> >> >> >> > class >> >> >> >> > declaration as a pseudo-scope, but contrasting these two >> options >> >> >> >> > as >> >> >> >> > if >> >> >> >> > they >> >> >> >> > are binary is not accurate: hard private through >> >> >> >> > module/function/block >> >> >> >> > scope >> >> >> >> > already exists, it is just difficult to work with in the >> context >> >> >> >> > of >> >> >> >> > shared >> >> >> >> > prototypes — one must either use WeakMaps, technically giving >> >> >> >> > _hardness_ >> >> >> >> > because of the forgeability of `global.WeakMap` / >> >> >> >> > `WeakMap.prototype` >> >> >> >> > / >> >> >> >> > `WeakMap.prototype.get|has|set`, or be willing to either not >> worry >> >> >> >> > about >> >> >> >> > garbage collection or implement it manually. This could be >> solved >> >> >> >> > for >> >> >> >> > with a >> >> >> >> > few rather undramatic changes, though. >> >> >> >> > >> >> >> >> > Notably, the first post there lists the following as a >> >> >> >> > disadvantage >> >> >> >> > of >> >> >> >> > the >> >> >> >> > soft model it describes: >> >> >> >> > >> >> >> >> >> Platform objects, both within ECMAScript and in embedding >> >> >> >> >> environments, >> >> >> >> >> contain hard private state. If a library wants to be >> >> >> >> >> high-fidelity >> >> >> >> >> and >> >> >> >> >> just >> >> >> >> >> like a platform object, soft-private state does not provide >> this >> >> >> >> >> (@domenic) >> >> >> >> > >> >> >> >> > ...but neither model there quite covers that use case. Platform >> >> >> >> > objects >> >> >> >> > _can_ see each other’s private state (cf the `isView` example >> >> >> >> > earlier, >> >> >> >> > or >> >> >> >> > scan the DOM API specs / Chrome source a bit to find numerous >> >> >> >> > examples). >> >> >> >> > It’s only the ES layer interacting with their interfaces that >> >> >> >> > cannot. >> >> >> >> > >> >> >> >> > Such things can be achieved with ordinary scope, which is why >> the >> >> >> >> > WeakMap >> >> >> >> > pattern has worked in practice in my experience to date, while >> >> >> >> > class-declaration-scoped privacy has not. It isn’t uncommon >> for a >> >> >> >> > library’s >> >> >> >> > exposed interface to be composed of an object graph, where >> privacy >> >> >> >> > is >> >> >> >> > a >> >> >> >> > concern at this public interface level, but library internal >> state >> >> >> >> > may >> >> >> >> > be >> >> >> >> > interconnected in unexposed ways under the hood. The most >> familiar >> >> >> >> > example >> >> >> >> > of this is a DOM node tree. As an experiment, perhaps try to >> >> >> >> > implement >> >> >> >> > the >> >> >> >> > relationships between HTMLFormElement, >> HTMLFormControlsCollection >> >> >> >> > and >> >> >> >> > the >> >> >> >> > various form control elements using either the main private >> fields >> >> >> >> > proposal >> >> >> >> > or your alternative proposal and see what happens. >> >> >> >> > >> >> >> >> >> However, the guardian logic tries to verify that the function >> >> >> >> >> trying >> >> >> >> >> to >> >> >> >> >> access the private fields of an instance is a member of the >> same >> >> >> >> >> or >> >> >> >> >> descending prototype that was used to create that instance. >> >> >> >> > >> >> >> >> > Because I’m looking at this in terms of slots, I’d first point >> out >> >> >> >> > that >> >> >> >> > prototypes don’t determine slottedness, the execution of some >> >> >> >> > specific >> >> >> >> > constructor does. It’s during this process that slots are >> >> >> >> > associated >> >> >> >> > with >> >> >> >> > the newly minted object by its identity. But even the current >> >> >> >> > private >> >> >> >> > fields >> >> >> >> > proposal tracks this behavior closely, and I’m not sure how >> else >> >> >> >> > it >> >> >> >> > could >> >> >> >> > work. The [[Prototype]] slot of an object is typically mutable >> >> >> >> > (`R|O.setPrototypeOf`, `__proto__`) and forgeable (Proxy’s >> >> >> >> > `getPrototypeOf` >> >> >> >> > trap). Why/how would its value matter when it comes to >> accessing >> >> >> >> > private >> >> >> >> > state? >> >> >> >> > >> >> >> >> > ```js >> >> >> >> > const pattern = /foo/; >> >> >> >> > Reflect.setPrototypeOf(pattern, Date.prototype); >> >> >> >> > pattern instanceof Date; // true >> >> >> >> > pattern instanceof RegExp; // false >> >> >> >> > pattern.getMinutes(); // throws TypeError because [[DateValue]] >> >> >> >> > slot >> >> >> >> > is >> >> >> >> > missing >> >> >> >> > RegExp.prototype.exec.call(pattern, 'foo'); // works; object >> has >> >> >> >> > RegExp >> >> >> >> > private slots >> >> >> >> > ``` >> >> >> >> > >> >> >> >> >> If I removed that requirement, it would work. However, >> there'd be >> >> >> >> >> no >> >> >> >> >> way >> >> >> >> >> to keep the private data from being leaked. Sadly, it's all or >> >> >> >> >> nothing >> >> >> >> >> with >> >> >> >> >> this approach. Hard private or soft private, those are the >> only >> >> >> >> >> choices. >> >> >> >> > >> >> >> >> > In the context of what you’ve described here this may be true, >> but >> >> >> >> > no >> >> >> >> > such >> >> >> >> > limitation presently exists. We can already do all this — hard, >> >> >> >> > leak-free >> >> >> >> > privacy, brandedness, “friends” etc — with scopes and WeakMaps, >> >> >> >> > but >> >> >> >> > for >> >> >> >> > the >> >> >> >> > fact that the `WeakMap` intrinsics may be forged. So what’s >> >> >> >> > baffled >> >> >> >> > me >> >> >> >> > is >> >> >> >> > this: why are all the proposals exploring this space not >> >> >> >> > addressing >> >> >> >> > that >> >> >> >> > relatively simple existing problem, and instead starting off >> from >> >> >> >> > a >> >> >> >> > place of >> >> >> >> > significant new complexity? You said “maybe after the private >> >> >> >> > fields >> >> >> >> > problem >> >> >> >> > has been resolved, someone will figure out a better way to >> handle >> >> >> >> > your >> >> >> >> > use >> >> >> >> > cases,” but I’d have hoped for the opposite — I want the >> primitive >> >> >> >> > building >> >> >> >> > blocks which things like class field syntax could be built >> over, >> >> >> >> > if >> >> >> >> > it >> >> >> >> > is >> >> >> >> > found that they are still necessary once the root issue is >> solved >> >> >> >> > for. >> >> >> >> > >> >> >> >> >> The main reason the privacy is set on a declaration level is >> >> >> >> >> because >> >> >> >> >> scope-level inheritance isn't very good for class-oriented >> >> >> >> >> inheritance. >> >> >> >> > >> >> >> >> > Can you explain this more? I’m not sure what’s meant by >> >> >> >> > “scope-level >> >> >> >> > inheritance” here. >> >> >> >> > >> >> >> >> >> I don't intend to stop [...] >> >> >> >> > >> >> >> >> > I very much admire your dedication! I’m also digging the >> >> >> >> > discussion. >> >> >> >> > I >> >> >> >> > think >> >> >> >> > we may be representing viewpoints at opposite extremes here, so >> >> >> >> > it’s >> >> >> >> > an >> >> >> >> > interesting contrast, but it also probably means we may be >> lacking >> >> >> >> > some >> >> >> >> > context for understanding one another’s angles. I’d be curious >> to >> >> >> >> > hear >> >> >> >> > more >> >> >> >> > about what you see as the problems with the current fields >> >> >> >> > proposal + >> >> >> >> > how >> >> >> >> > your members proposal would solve them; the repo readme didn’t >> >> >> >> > seem >> >> >> >> > to >> >> >> >> > include a rationale section. >> >> >> >> > >> >> >> >> > On Sat, Jul 28, 2018 at 10:30 PM Ranando King < >> king...@gmail.com> >> >> >> >> > wrote: >> >> >> >> >> >> >> >> >> >> I've almost given up on making any significant headway in >> either >> >> >> >> >> adjusting >> >> >> >> >> or flat-out correcting the flaws in that proposal, but I don't >> >> >> >> >> intend >> >> >> >> >> to >> >> >> >> >> stop trying until either we get stuck with that proposal, or >> they >> >> >> >> >> understand >> >> >> >> >> and accept what I'm telling them, or logically prove that my >> >> >> >> >> concerns >> >> >> >> >> are >> >> >> >> >> either irrational or inconsequential. >> >> >> >> >> >> >> >> >> >> > Private object state in particular is only _made complex_ by >> >> >> >> >> > associating >> >> >> >> >> > it with declarations instead of scopes that happen to >> contain >> >> >> >> >> > declarations >> >> >> >> >> > (or into which constructors are passed, etc). The >> complexity is >> >> >> >> >> > artificial — >> >> >> >> >> > not a good sign imo. >> >> >> >> >> >> >> >> >> >> That's not quite right. What you're essentially asking for is >> a >> >> >> >> >> violatable >> >> >> >> >> private field, or as has been described by others, a "soft >> >> >> >> >> private". >> >> >> >> >> Since >> >> >> >> >> we agree that the "friendly" & "befriend" pair is a somewhat >> (if >> >> >> >> >> not >> >> >> >> >> completely) bad idea, I'm going to take 1 more pass at your 3 >> >> >> >> >> requests >> >> >> >> >> with >> >> >> >> >> a different angle. >> >> >> >> >> >> >> >> >> >> > Adding the same “slot” to multiple classes which don’t >> inherit >> >> >> >> >> > from >> >> >> >> >> > each >> >> >> >> >> > other >> >> >> >> >> > Selectively sharing access to private state through >> functions >> >> >> >> >> > declared >> >> >> >> >> > outside the class body >> >> >> >> >> >> >> >> >> >> ```js >> >> >> >> >> //Using my proposal >> >> >> >> >> var {A, B, C} = (() => { >> >> >> >> >> const common = Symbol("common"); >> >> >> >> >> >> >> >> >> >> class A { >> >> >> >> >> private [common] = 1; >> >> >> >> >> add(...args) { >> >> >> >> >> var retval = this#[common]; >> >> >> >> >> for (let obj of args) { >> >> >> >> >> retval += obj#[common]; >> >> >> >> >> } >> >> >> >> >> return retval; >> >> >> >> >> } >> >> >> >> >> } >> >> >> >> >> class B { >> >> >> >> >> private [common] = 2; >> >> >> >> >> optional() { >> >> >> >> >> console.log(`common member = ${this#[common]}`); >> >> >> >> >> } >> >> >> >> >> } >> >> >> >> >> var C = { >> >> >> >> >> private [common]: 3, >> >> >> >> >> required() { >> >> >> >> >> console.log(`common member = ${this#[common]}`); >> >> >> >> >> } >> >> >> >> >> } >> >> >> >> >> >> >> >> >> >> return { A, B, C }; >> >> >> >> >> })(); >> >> >> >> >> >> >> >> >> >> //So you want the following statement to not throw a TypeError >> >> >> >> >> and >> >> >> >> >> return >> >> >> >> >> 6 >> >> >> >> >> (new A()).add(new B(), C); >> >> >> >> >> ``` >> >> >> >> >> I'm not sure I can make this work in my proposal, and I'm >> >> >> >> >> absolutely >> >> >> >> >> sure >> >> >> >> >> you'd be flatly refused by the other proposal. If a `Symbol` >> is >> >> >> >> >> provided as >> >> >> >> >> the `[[IdentifierName]]` of a private or protected field, >> then I >> >> >> >> >> can >> >> >> >> >> let >> >> >> >> >> that `Symbol` be both the key and value that are added to the >> >> >> >> >> `[[DeclarationInfo]]` and `[[InheritanceInfo]]` records. That >> way >> >> >> >> >> there >> >> >> >> >> will >> >> >> >> >> be a common private field name usable by all 3 objects. >> However, >> >> >> >> >> the >> >> >> >> >> guardian logic tries to verify that the function trying to >> access >> >> >> >> >> the >> >> >> >> >> private fields of an instance is a member of the same or >> >> >> >> >> descending >> >> >> >> >> prototype that was used to create that instance. If I removed >> >> >> >> >> that >> >> >> >> >> requirement, it would work. However, there'd be no way to keep >> >> >> >> >> the >> >> >> >> >> private >> >> >> >> >> data from being leaked. Sadly, it's all or nothing with this >> >> >> >> >> approach. >> >> >> >> >> Hard >> >> >> >> >> private or soft private, those are the only choices. The TC39 >> >> >> >> >> board >> >> >> >> >> has >> >> >> >> >> already decided that what they want new syntax for is hard >> >> >> >> >> private. >> >> >> >> >> >> >> >> >> >> > Adding slots dynamically, e.g. when adding mix-in methods >> that >> >> >> >> >> > may >> >> >> >> >> > initialize a new slot if necessary when called, since >> >> >> >> >> > subclassing >> >> >> >> >> > is >> >> >> >> >> > not >> >> >> >> >> > always appropriate >> >> >> >> >> >> >> >> >> >> Because the TC39 board has set their sights on hard private, >> this >> >> >> >> >> will >> >> >> >> >> require new syntax like what I suggested earlier Adding >> private >> >> >> >> >> members >> >> >> >> >> dynamically would also pose a leak risk if it could be done >> after >> >> >> >> >> the >> >> >> >> >> prototype has been fully constructed. The main reason the >> privacy >> >> >> >> >> is >> >> >> >> >> set on >> >> >> >> >> a declaration level is because scope-level inheritance isn't >> very >> >> >> >> >> good >> >> >> >> >> for >> >> >> >> >> `class`-oriented inheritance. The `class` keyword was >> provided to >> >> >> >> >> simplify >> >> >> >> >> the vertical inheritance model, along with some API to enable >> >> >> >> >> inheritance >> >> >> >> >> from native objects even without using `class`. The syntax >> >> >> >> >> changes >> >> >> >> >> for >> >> >> >> >> simplifying private field declaration are just an extension of >> >> >> >> >> that. >> >> >> >> >> Even >> >> >> >> >> though it's not unusual for some developers to spend a lot of >> >> >> >> >> time >> >> >> >> >> working >> >> >> >> >> with fringe use-cases, syntax changes are almost always going >> to >> >> >> >> >> be >> >> >> >> >> made for >> >> >> >> >> the most common use cases first. Maybe after the private >> fields >> >> >> >> >> problem >> >> >> >> >> has >> >> >> >> >> been resolved, someone will figure out a better way to handle >> >> >> >> >> your >> >> >> >> >> use >> >> >> >> >> cases. >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> On Sat, Jul 28, 2018 at 3:52 PM Darien Valentine >> >> >> >> >> <valentin...@gmail.com> >> >> >> >> >> wrote: >> >> >> >> >>> >> >> >> >> >>> > Are you saying you want multiple non-hierarchally related >> >> >> >> >>> > classes >> >> >> >> >>> > to >> >> >> >> >>> > have an instance private field with shared name [...] >> >> >> >> >>> >> >> >> >> >>> Yeah. This is a hard problem to solve when trying to >> integrate >> >> >> >> >>> private >> >> >> >> >>> fields with class syntax, but it’s not a problem at all when >> >> >> >> >>> privacy >> >> >> >> >>> is a >> >> >> >> >>> more generic tool based on scope. This also isn’t a foreign >> >> >> >> >>> concept >> >> >> >> >>> in >> >> >> >> >>> ES: >> >> >> >> >>> consider this intrinsic method: >> >> >> >> >>> >> >> >> >> >>> https://tc39.github.io/ecma262/#sec-arraybuffer.isview >> >> >> >> >>> >> >> >> >> >>> This method returns true if the argument has the >> >> >> >> >>> `[[ViewedArrayBuffer]]` >> >> >> >> >>> slot. This slot exists on genuine instances of both >> >> >> >> >>> `%TypedArray%` >> >> >> >> >>> and >> >> >> >> >>> `%DataView%`, but they do not receive these slots by way of >> >> >> >> >>> inheritance from >> >> >> >> >>> a common constructor. There are similar cases in HTML host >> APIs. >> >> >> >> >>> >> >> >> >> >>> > The befriend keyword would allow an object to request >> >> >> >> >>> > friendship >> >> >> >> >>> > with >> >> >> >> >>> > an existing friendly object. I'm not sure this is a good >> idea, >> >> >> >> >>> > though. >> >> >> >> >>> >> >> >> >> >>> I don’t think it is either, no. It’s too much complexity for >> too >> >> >> >> >>> little >> >> >> >> >>> gain. But again, this is achievable “for free” just by >> divorcing >> >> >> >> >>> “private >> >> >> >> >>> object state” from class declarations (or object literals). I >> >> >> >> >>> would >> >> >> >> >>> ask: >> >> >> >> >>> what problem is solved by making this a feature of the >> >> >> >> >>> declarations >> >> >> >> >>> themselves? Does it merit the complexity and the hoop jumping >> >> >> >> >>> needed >> >> >> >> >>> to >> >> >> >> >>> handle edge cases?\* >> >> >> >> >>> >> >> >> >> >>> \* One person’s edge case; another’s everyday concern haha. >> >> >> >> >>> >> >> >> >> >>> > The example you gave above still declares the functions in >> >> >> >> >>> > question >> >> >> >> >>> > inside the class body, so that's not really a solution. >> >> >> >> >>> >> >> >> >> >>> If you’re referring to the first example, that is a >> >> >> >> >>> demonstration >> >> >> >> >>> of >> >> >> >> >>> what >> >> >> >> >>> is possible using the existing stage 3 class fields proposal >> as >> >> >> >> >>> implemented >> >> >> >> >>> in Chrome. It isn’t what I want; it’s what’s necessary to >> >> >> >> >>> achieve >> >> >> >> >>> this >> >> >> >> >>> with >> >> >> >> >>> the current stage 3 proposed model. >> >> >> >> >>> >> >> >> >> >>> > Sounds to me like you'd love for class syntax to look like >> >> >> >> >>> > this >> >> >> >> >>> > [[example with mixin syntax in declaration]] >> >> >> >> >>> >> >> >> >> >>> Perhaps — it’s interesting for sure! But the pattern that >> >> >> >> >>> already >> >> >> >> >>> works, >> >> >> >> >>> `mixin(Cstr)`, is not presently a source of problems for me. >> >> >> >> >>> Private >> >> >> >> >>> object >> >> >> >> >>> state in particular is only _made complex_ by associating it >> >> >> >> >>> with >> >> >> >> >>> declarations instead of scopes that happen to contain >> >> >> >> >>> declarations >> >> >> >> >>> (or >> >> >> >> >>> into >> >> >> >> >>> which constructors are passed, etc). The complexity is >> >> >> >> >>> artificial — >> >> >> >> >>> not a >> >> >> >> >>> good sign imo. >> >> >> >> >>> >> >> >> >> >>> > One thing both proposal-class-fields and >> >> >> >> >>> > proposal-object-members >> >> >> >> >>> > have >> >> >> >> >>> > in common is that the focus is on producing >> instance-private >> >> >> >> >>> > fields. >> >> >> >> >>> > All 3 >> >> >> >> >>> > of the scenarios you presented lay outside of that focus >> for >> >> >> >> >>> > one >> >> >> >> >>> > reason or >> >> >> >> >>> > another. >> >> >> >> >>> >> >> >> >> >>> Both the WeakMap solution and the stub concept I provided >> after >> >> >> >> >>> are >> >> >> >> >>> more >> >> >> >> >>> generic than privacy in either of those proposals. When I say >> >> >> >> >>> "object >> >> >> >> >>> private state," it’s true that the object in question could >> be >> >> >> >> >>> any >> >> >> >> >>> object. >> >> >> >> >>> But in practice, any realization of the feature would pertain >> >> >> >> >>> chiefly >> >> >> >> >>> to >> >> >> >> >>> class instances, and the examples I gave, though contrived, >> do >> >> >> >> >>> concern >> >> >> >> >>> class >> >> >> >> >>> instances. The reason private object state is chiefly an >> issue >> >> >> >> >>> of >> >> >> >> >>> class >> >> >> >> >>> instances stems directly from the nature of prototype methods >> >> >> >> >>> and >> >> >> >> >>> accessors, >> >> >> >> >>> so if you are not making use of prototypes, you could instead >> >> >> >> >>> have >> >> >> >> >>> used a >> >> >> >> >>> closure+factory directly. >> >> >> >> >>> >> >> >> >> >>> --- >> >> >> >> >>> >> >> >> >> >>> In a nutshell, my issue with existing proposals could >> probably >> >> >> >> >>> be >> >> >> >> >>> summarized as a concern that they are neither as generic nor >> as >> >> >> >> >>> simple >> >> >> >> >>> as >> >> >> >> >>> native slots. To be clear, proper “slots” are an internal >> >> >> >> >>> concept, >> >> >> >> >>> only >> >> >> >> >>> observable indirectly — but they are the special sauce >> >> >> >> >>> underlying a >> >> >> >> >>> number >> >> >> >> >>> of behaviors which are presently awkward to achieve in ES >> code >> >> >> >> >>> itself, >> >> >> >> >>> and >> >> >> >> >>> they are a nice simple model of private object state which is >> >> >> >> >>> tantalizingly >> >> >> >> >>> close to, but not _exactly_ the same as in two critical ways, >> >> >> >> >>> symbol >> >> >> >> >>> keyed >> >> >> >> >>> properties. That said, “real” slots would continue to have an >> >> >> >> >>> advantage with >> >> >> >> >>> regard to cross-realm stuff even if private symbol keys >> existed. >> >> >> >> >>> >> >> >> >> >>> That such a model is radically simpler — minmax and all that >> — >> >> >> >> >>> feels >> >> >> >> >>> very >> >> >> >> >>> important to me, but I dunno. I’m not holding my breath for >> big >> >> >> >> >>> changes >> >> >> >> >>> here. The current stage 3 proposal seems to be unstoppable; >> much >> >> >> >> >>> smarter / >> >> >> >> >>> more important people than me have already tried and failed. >> :) >> >> >> >> >>> >> >> >> >> >>> >> >> >> >> >>> On Sat, Jul 28, 2018 at 3:14 PM Ranando King < >> king...@gmail.com> >> >> >> >> >>> wrote: >> >> >> >> >>>> >> >> >> >> >>>> In a word... wow. You've got me thinking hard here. Those >> are >> >> >> >> >>>> some >> >> >> >> >>>> peculiar use cases, and they do a great job of highlighting >> why >> >> >> >> >>>> someone >> >> >> >> >>>> might forego using `class`. One thing both >> >> >> >> >>>> proposal-class-fields >> >> >> >> >>>> and >> >> >> >> >>>> proposal-object-members have in common is that the focus is >> on >> >> >> >> >>>> producing >> >> >> >> >>>> instance-private fields. All 3 of the scenarios you >> presented >> >> >> >> >>>> lay >> >> >> >> >>>> outside of >> >> >> >> >>>> that focus for one reason or another. >> >> >> >> >>>> >> >> >> >> >>>> > Adding the same “slot” to multiple classes which don’t >> >> >> >> >>>> > inherit >> >> >> >> >>>> > from >> >> >> >> >>>> > each other >> >> >> >> >>>> >> >> >> >> >>>> I'm a little confused by this one. Are you saying you want >> >> >> >> >>>> multiple >> >> >> >> >>>> non-hierarchally related classes to have an instance private >> >> >> >> >>>> field >> >> >> >> >>>> with >> >> >> >> >>>> shared name, such that the same private field name refers >> to a >> >> >> >> >>>> distinct and >> >> >> >> >>>> separate field on each instance of every such class, but >> where >> >> >> >> >>>> any >> >> >> >> >>>> such >> >> >> >> >>>> instance can have that field referenced by that shared name >> >> >> >> >>>> from >> >> >> >> >>>> any >> >> >> >> >>>> member >> >> >> >> >>>> function of the corresponding classes? (Wow that was wordy >> to >> >> >> >> >>>> write >> >> >> >> >>>> out...) >> >> >> >> >>>> If this is what you meant, you're describing friend classes. >> >> >> >> >>>> The >> >> >> >> >>>> top-down >> >> >> >> >>>> processing nature of ES makes this a difficult thing to >> create >> >> >> >> >>>> a >> >> >> >> >>>> clean >> >> >> >> >>>> syntax for without risking leaking the private state or >> >> >> >> >>>> fundamentally >> >> >> >> >>>> altering how ES is processed. Mutual friendship is even >> harder. >> >> >> >> >>>> >> >> >> >> >>>> ... and yet I just thought of a way to do it. By telling you >> >> >> >> >>>> this >> >> >> >> >>>> I'm >> >> >> >> >>>> leaving myself to consider writing a proposal containing 2 >> new >> >> >> >> >>>> keywords: >> >> >> >> >>>> `befriend` and `friendly`. I don't know if this can be done >> >> >> >> >>>> with >> >> >> >> >>>> the >> >> >> >> >>>> existing proposal being what it is. However, with my >> proposal, >> >> >> >> >>>> there's a >> >> >> >> >>>> chance. The `friendly` keyword would declare that an object >> is >> >> >> >> >>>> prepared to >> >> >> >> >>>> share select information with any object that befriends it. >> The >> >> >> >> >>>> `befriend` >> >> >> >> >>>> keyword would allow an object to request friendship with an >> >> >> >> >>>> existing >> >> >> >> >>>> friendly object. I'm not sure this is a good idea, though. >> This >> >> >> >> >>>> means >> >> >> >> >>>> that >> >> >> >> >>>> any object declared 'friendly' is automatically insecure as >> all >> >> >> >> >>>> it >> >> >> >> >>>> takes to >> >> >> >> >>>> gain access to the selected members of its private space >> would >> >> >> >> >>>> be >> >> >> >> >>>> to >> >> >> >> >>>> 'befriend' it. >> >> >> >> >>>> >> >> >> >> >>>> > Selectively sharing access to private state through >> functions >> >> >> >> >>>> > declared >> >> >> >> >>>> > outside the class body >> >> >> >> >>>> >> >> >> >> >>>> The example you gave above still declares the functions in >> >> >> >> >>>> question >> >> >> >> >>>> inside the `class` body, so that's not really a solution. If >> >> >> >> >>>> the >> >> >> >> >>>> example you >> >> >> >> >>>> gave actually solves your use case, then what you're asking >> for >> >> >> >> >>>> here >> >> >> >> >>>> isn't >> >> >> >> >>>> even needed. If, however, that was a bad example, then it >> >> >> >> >>>> sounds >> >> >> >> >>>> like >> >> >> >> >>>> you're >> >> >> >> >>>> looking for friend functions. See the previous section. >> >> >> >> >>>> >> >> >> >> >>>> > Adding slots dynamically, e.g. when adding mix-in methods >> >> >> >> >>>> > that >> >> >> >> >>>> > may >> >> >> >> >>>> > initialize a new slot if necessary when called, since >> >> >> >> >>>> > subclassing >> >> >> >> >>>> > is not >> >> >> >> >>>> > always appropriate >> >> >> >> >>>> >> >> >> >> >>>> Sounds to me like you'd love for `class` syntax to look like >> >> >> >> >>>> this: >> >> >> >> >>>> >> >> >> >> >>>> ```js >> >> >> >> >>>> class [<identifierName1>] [extends <identifierName2>] [mixes >> >> >> >> >>>> <identifierName3>[, <identifierName3>[, ...]]] { ... } >> >> >> >> >>>> ``` >> >> >> >> >>>> so that the private fields of the objects in the `mixes` >> list >> >> >> >> >>>> are >> >> >> >> >>>> added >> >> >> >> >>>> to the set of private fields provided by the `class` >> definition >> >> >> >> >>>> directly. >> >> >> >> >>>> That would also require another proposal, but I think that >> can >> >> >> >> >>>> be >> >> >> >> >>>> done >> >> >> >> >>>> regardless of which instance-private fields proposal gets >> >> >> >> >>>> accepted. >> >> >> >> >>>> >> >> >> >> >>>> On Sat, Jul 28, 2018 at 12:49 PM Darien Valentine >> >> >> >> >>>> <valentin...@gmail.com> wrote: >> >> >> >> >>>>> >> >> >> >> >>>>> To put this another, much briefer way, here’s a >> hypothetical >> >> >> >> >>>>> model >> >> >> >> >>>>> for >> >> >> >> >>>>> associating private state with objects that would cover me. >> >> >> >> >>>>> Privacy >> >> >> >> >>>>> would be >> >> >> >> >>>>> provided... >> >> >> >> >>>>> >> >> >> >> >>>>> 1. in the form of symbolic keys whose presence cannot be >> >> >> >> >>>>> observed >> >> >> >> >>>>> (i.e., they would not be exposed by >> `getOwnPropertySymbols`) >> >> >> >> >>>>> 2. and which have a syntactic declaration so that one can >> be >> >> >> >> >>>>> sure >> >> >> >> >>>>> they >> >> >> >> >>>>> are really getting private keys (i.e., an api like >> >> >> >> >>>>> `Symbol.private()` >> >> >> >> >>>>> wouldn’t work) >> >> >> >> >>>>> >> >> >> >> >>>>> ``` >> >> >> >> >>>>> const bar = private(); >> >> >> >> >>>>> >> >> >> >> >>>>> // alternatively: const #bar; could be anything so long as >> >> >> >> >>>>> it’s >> >> >> >> >>>>> syntactic >> >> >> >> >>>>> >> >> >> >> >>>>> class Foo { >> >> >> >> >>>>> constructor() { >> >> >> >> >>>>> this[bar] = 1; >> >> >> >> >>>>> } >> >> >> >> >>>>> } >> >> >> >> >>>>> >> >> >> >> >>>>> // etc >> >> >> >> >>>>> ``` >> >> >> >> >>>>> >> >> >> >> >>>>> The keys would be typeof 'symbol'; the only difference >> being >> >> >> >> >>>>> that >> >> >> >> >>>>> they >> >> >> >> >>>>> are symbols which are flagged as private when created. They >> >> >> >> >>>>> would >> >> >> >> >>>>> be >> >> >> >> >>>>> permitted only in syntactic property assignments and >> accesses. >> >> >> >> >>>>> Existing >> >> >> >> >>>>> reflection utilities would disallow the use or appearance >> of >> >> >> >> >>>>> such >> >> >> >> >>>>> symbols >> >> >> >> >>>>> both to ensure privacy and to maintain the invariant that >> they >> >> >> >> >>>>> are >> >> >> >> >>>>> always >> >> >> >> >>>>> simple data properties: >> >> >> >> >>>>> >> >> >> >> >>>>> ```js >> >> >> >> >>>>> Reflect.defineProperty({}, #bar, { ... }); // throws type >> >> >> >> >>>>> error >> >> >> >> >>>>> Object.getOwnPropertyDescriptors(someObjWithAPrivateSlot); >> // >> >> >> >> >>>>> does >> >> >> >> >>>>> not >> >> >> >> >>>>> include it >> >> >> >> >>>>> foo[bar] = 2; // fine >> >> >> >> >>>>> ``` >> >> >> >> >>>>> >> >> >> >> >>>>> This is significantly simpler than what’s in flight both in >> >> >> >> >>>>> terms >> >> >> >> >>>>> of >> >> >> >> >>>>> syntax and mechanics, which makes me suspicious that I’m >> >> >> >> >>>>> probably >> >> >> >> >>>>> ignoring >> >> >> >> >>>>> things that other people find important. However it would >> >> >> >> >>>>> bring >> >> >> >> >>>>> parity to ES >> >> >> >> >>>>> objects wrt being able to implement genuinely private >> slots in >> >> >> >> >>>>> userland with >> >> >> >> >>>>> the same flexibility as what is done internally. >> >> >> >> >>>>> >> >> >> >> >>>>> In total, this entails a new primary expression, a boolean >> >> >> >> >>>>> flag >> >> >> >> >>>>> associated with symbol values, and an extra step added to >> >> >> >> >>>>> several >> >> >> >> >>>>> algorithms >> >> >> >> >>>>> associated with Object and Reflect. >> >> >> >> >>>>> _______________________________________________ >> >> >> >> >>>>> es-discuss mailing list >> >> >> >> >>>>> es-discuss@mozilla.org >> >> >> >> >>>>> https://mail.mozilla.org/listinfo/es-discuss >> >> >> >> > >> >> >> >> > >> >> >> >> > _______________________________________________ >> >> >> >> > es-discuss mailing list >> >> >> >> > es-discuss@mozilla.org >> >> >> >> > https://mail.mozilla.org/listinfo/es-discuss >> >> >> >> > >> >> >> >> _______________________________________________ >> >> >> >> es-discuss mailing list >> >> >> >> es-discuss@mozilla.org >> >> >> >> https://mail.mozilla.org/listinfo/es-discuss >> > _______________________________________________ > es-discuss mailing list > es-discuss@mozilla.org > https://mail.mozilla.org/listinfo/es-discuss >
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