Re: noSuchMethod: funargs + invoke-only-phantoms
(sorry, was in a small vacation, can't answer earlier) Yes, I'm perfectly aware about what host objects may do (there is even wide-spread phrase in JS community: do not trust to host objects, they can do almost anything). From this viewpoint, if to treat these proxies as host objects, then in fact any of discussed broken invariants can be justified. But, I wanted to consider them from the view of casual JS objects. Regarding the subtle difference, if to consider casual JS objects, then no, 8.12.7 (http://es5.github.com/#x8.12.7), step 3.a cleary states that the property is removed. Dmitry. On Wed, Dec 21, 2011 at 11:53 PM, Tom Van Cutsem tomvc...@gmail.com wrote: 2011/12/21 Dmitry Soshnikov dmitry.soshni...@gmail.com On 20.12.2011 17:00, Tom Van Cutsem wrote: You can (and probably should) advertise a virtual method as configurable:true. I can only `configurable: true', but as we said, to fix broken `delete' operator, we need to treat these virtual properties as non-configurable. We logically `return false' in `delete' trap and have to adjust `getOwnPropertyDescriptor' as well. This seems to be a persistent source of confusion about invariants in ES5: The fact that a property is configurable:true _implies_ that it can be successfully deleted is _not_ an ECMAScript invariant. The ES5 spec only requires that configurable:false implies that the property cannot successfully be deleted. The difference is subtle, but important. It would not surprise me if there exist host objects that advertise their properties as configurable:true, don't complain when you try to delete them, yet when you query the properties again, they're still there. This is entirely within the bounds of the ES5 spec. MarkM once explained the difference well: https://mail.mozilla.org/pipermail/es-discuss/2011-May/014150.html Cheers, Tom ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: noSuchMethod: funargs + invoke-only-phantoms
This is almost the exact behavior I was talking about ...
Object.withNoSuchMethod = function withNoSuchMethod(obj, __noSuchMethod__) {
var cachedInvokes = {};
return Proxy.create({
get: function (receiver, name) {
return name in obj ?
obj[name] :
cachedInvokes.hasOwnProperty(name) ?
cachedInvokes[name] :
cachedInvokes[name] = function () {
if(this === receiver)
return __noSuchMethod__.call(obj, name, arguments);
throw new Error(undefined is not a function);
}
;
}
});
};
var p = Object.withNoSuchMethod({/*generic object*/}, function (prop, args)
{
alert([prop, args.length]);
});
(p.test)(1, 2, 3);
var test = p.test;
test.call(p, 1, 2, 3);
test.apply(p, [1, 2, 3]);
p.test(1, 2, 3);
test.bind(p)(1, 2, 3);
test(1, 2, 3); // undefined is not a function
test.call(null, 1, 2, 3); // undefined is not a function
On Tue, Dec 20, 2011 at 2:00 PM, Tom Van Cutsem tomvc...@gmail.com wrote:
- @Tom: Found bugs in DirectProxies.js
Thanks for reporting, but I don't think these are bugs:
1. Properties created via assignment gets `false' value for descriptor
attributes; should be true. E.g. foo.bar = 10, where `foo' is direct proxy,
makes bar non-configurable
I can't reproduce this. Both in tracemonkey and ff8 I get the following:
js var t = {}
js var p = Proxy(t, {})
js p.x = 1
1
js Object.getOwnPropertyDescriptor(t, 'x')
({value:1, writable:true, enumerable:true, configurable:true})
js Object.getOwnPropertyDescriptor(p, 'x')
({value:1, writable:true, enumerable:true, configurable:true})
There is, however, a TM-specific bug that I suspect may be the cause of
your observed non-configurable by default behavior:
https://bugzilla.mozilla.org/show_bug.cgi?id=601329
2. Can't return descriptor with `configurable: false' for non-existing
property; get: cannot report a non-configurable descriptor for
non-existent property But we need it in case virtual methods
You can (and probably should) advertise a virtual method as
configurable:true.
The proxy throws this exception because, for properties that do not exist
on the wrapped target, it cannot guarantee that they will always be
non-configurable. For example, if your proxy handler now says that foo is
{value:10, configurable:false}, nothing stops your proxy handler from later
claiming that foo is {value:0, configurable:true}.
Cheers,
Tom
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Re: noSuchMethod: funargs + invoke-only-phantoms
On 20.12.2011 17:00, Tom Van Cutsem wrote:
- @Tom: Found bugs in DirectProxies.js
Thanks for reporting, but I don't think these are bugs:
1. Properties created via assignment gets `false' value for
descriptor attributes; should be true. E.g. foo.bar = 10, where
`foo' is direct proxy, makes bar non-configurable
I can't reproduce this. Both in tracemonkey and ff8 I get the following:
js var t = {}
js var p = Proxy(t, {})
js p.x = 1
1
js Object.getOwnPropertyDescriptor(t, 'x')
({value:1, writable:true, enumerable:true, configurable:true})
js Object.getOwnPropertyDescriptor(p, 'x')
({value:1, writable:true, enumerable:true, configurable:true})
There is, however, a TM-specific bug that I suspect may be the cause
of your observed non-configurable by default behavior:
https://bugzilla.mozilla.org/show_bug.cgi?id=601329
Hm, I can't reproduce it either now (latest release Firefox, WinXP).
Perhaps it was really the bug you noticed with my Firefox at work.
2. Can't return descriptor with `configurable: false' for
non-existing property; get: cannot report a non-configurable
descriptor for non-existent property But we need it in case
virtual methods
You can (and probably should) advertise a virtual method as
configurable:true.
I can only `configurable: true', but as we said, to fix broken `delete'
operator, we need to treat these virtual properties as non-configurable.
We logically `return false' in `delete' trap and have to adjust
`getOwnPropertyDescriptor' as well.
Well, how to say have to...? It just seems the most logical
justification of this broken invariant -- to treat them as
non-configurable. Yes, and by the way, also as non-enumerable since they
will not appear in the for-in.
The proxy throws this exception because, for properties that do not
exist on the wrapped target, it cannot guarantee that they will always
be non-configurable.
What to do with these virtual properties then? It would be good to have
them {configurable: false, enumerable: false, writable: true, value:
noSuchMethodActivator}
For example, if your proxy handler now says that foo is {value:10,
configurable:false}, nothing stops your proxy handler from later
claiming that foo is {value:0, configurable:true}.
Wait, but we can do the same for any property, including existing. Or am
I missing something?
Cheers,
Dmitry.
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Re: noSuchMethod: funargs + invoke-only-phantoms
Funny implementation :P You did it vice-versa: functional objects _do_
work, but simple calls do not :D
No, not good to depend on `this' value and non-Reference type.
Dmitry.
On 21.12.2011 16:05, Andrea Giammarchi wrote:
This is almost the exact behavior I was talking about ...
Object.withNoSuchMethod = function withNoSuchMethod(obj,
__noSuchMethod__) {
var cachedInvokes = {};
return Proxy.create({
get: function (receiver, name) {
return name in obj ?
obj[name] :
cachedInvokes.hasOwnProperty(name) ?
cachedInvokes[name] :
cachedInvokes[name] = function () {
if(this === receiver)
return __noSuchMethod__.call(obj, name, arguments);
throw new Error(undefined is not a function);
}
;
}
});
};
var p = Object.withNoSuchMethod({/*generic object*/}, function (prop,
args) {
alert([prop, args.length]);
});
(p.test)(1, 2, 3);
var test = p.test;
test.call(p, 1, 2, 3);
test.apply(p, [1, 2, 3]);
p.test(1, 2, 3);
test.bind(p)(1, 2, 3);
test(1, 2, 3); // undefined is not a function
test.call(null, 1, 2, 3); // undefined is not a function
On Tue, Dec 20, 2011 at 2:00 PM, Tom Van Cutsem tomvc...@gmail.com
mailto:tomvc...@gmail.com wrote:
- @Tom: Found bugs in DirectProxies.js
Thanks for reporting, but I don't think these are bugs:
1. Properties created via assignment gets `false' value for
descriptor attributes; should be true. E.g. foo.bar = 10,
where `foo' is direct proxy, makes bar non-configurable
I can't reproduce this. Both in tracemonkey and ff8 I get the
following:
js var t = {}
js var p = Proxy(t, {})
js p.x = 1
1
js Object.getOwnPropertyDescriptor(t, 'x')
({value:1, writable:true, enumerable:true, configurable:true})
js Object.getOwnPropertyDescriptor(p, 'x')
({value:1, writable:true, enumerable:true, configurable:true})
There is, however, a TM-specific bug that I suspect may be the
cause of your observed non-configurable by default behavior:
https://bugzilla.mozilla.org/show_bug.cgi?id=601329
2. Can't return descriptor with `configurable: false' for
non-existing property; get: cannot report a non-configurable
descriptor for non-existent property But we need it in case
virtual methods
You can (and probably should) advertise a virtual method as
configurable:true.
The proxy throws this exception because, for properties that do
not exist on the wrapped target, it cannot guarantee that they
will always be non-configurable. For example, if your proxy
handler now says that foo is {value:10, configurable:false},
nothing stops your proxy handler from later claiming that foo is
{value:0, configurable:true}.
Cheers,
Tom
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Re: noSuchMethod: funargs + invoke-only-phantoms
2011/12/21 Dmitry Soshnikov dmitry.soshni...@gmail.com On 20.12.2011 17:00, Tom Van Cutsem wrote: You can (and probably should) advertise a virtual method as configurable:true. I can only `configurable: true', but as we said, to fix broken `delete' operator, we need to treat these virtual properties as non-configurable. We logically `return false' in `delete' trap and have to adjust `getOwnPropertyDescriptor' as well. This seems to be a persistent source of confusion about invariants in ES5: The fact that a property is configurable:true _implies_ that it can be successfully deleted is _not_ an ECMAScript invariant. The ES5 spec only requires that configurable:false implies that the property cannot successfully be deleted. The difference is subtle, but important. It would not surprise me if there exist host objects that advertise their properties as configurable:true, don't complain when you try to delete them, yet when you query the properties again, they're still there. This is entirely within the bounds of the ES5 spec. MarkM once explained the difference well: https://mail.mozilla.org/pipermail/es-discuss/2011-May/014150.html Cheers, Tom ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: noSuchMethod: funargs + invoke-only-phantoms
- @Tom: Found bugs in DirectProxies.js
Thanks for reporting, but I don't think these are bugs:
1. Properties created via assignment gets `false' value for descriptor
attributes; should be true. E.g. foo.bar = 10, where `foo' is direct proxy,
makes bar non-configurable
I can't reproduce this. Both in tracemonkey and ff8 I get the following:
js var t = {}
js var p = Proxy(t, {})
js p.x = 1
1
js Object.getOwnPropertyDescriptor(t, 'x')
({value:1, writable:true, enumerable:true, configurable:true})
js Object.getOwnPropertyDescriptor(p, 'x')
({value:1, writable:true, enumerable:true, configurable:true})
There is, however, a TM-specific bug that I suspect may be the cause of
your observed non-configurable by default behavior:
https://bugzilla.mozilla.org/show_bug.cgi?id=601329
2. Can't return descriptor with `configurable: false' for non-existing
property; get: cannot report a non-configurable descriptor for
non-existent property But we need it in case virtual methods
You can (and probably should) advertise a virtual method as
configurable:true.
The proxy throws this exception because, for properties that do not exist
on the wrapped target, it cannot guarantee that they will always be
non-configurable. For example, if your proxy handler now says that foo is
{value:10, configurable:false}, nothing stops your proxy handler from later
claiming that foo is {value:0, configurable:true}.
Cheers,
Tom
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Re: noSuchMethod: funargs + invoke-only-phantoms
On 18.12.2011 2:51, Brendan Eich wrote: From: Dmitry Soshnikovdmitry.soshni...@gmail.com On 17.12.2011 17:21, Herby Vojčík wrote: Hello, from my point the scenario that: delete lib.toRussianName; then it still: typeof lib.toRussianName; // function, Trollface ;D is much more acceptable (it happens everyday - there are non-writable properties everywhere), Yes, good point on non-configurable properties. So, we may justify this broken invariant with `delete' which becomes not so broken. it's good. Not so fast: the result of the delete expression differs in the non-configurable case (false) from the no-such-property case (true). Right, we have to adjust `delete' trap as well. And, if we treat these virtual methods as non-configurable, the to adjust also `getOwnPropertyDescriptor' hook too. I edited the implementation: https://gist.github.com/1481018#L229 Still, some problems appear after that: - if we return descriptor at `getOwnPropertyDescriptor', potentially this means that the user can change some attributes via `Object.defineProperty'. E.g. to set `enumerable' to false, and we have to handle it in `defineProperty' hook. OTOH, if our property is non-configurable, it means user can't change some attribute values in `Object.defineProperty'. - @Tom: Found bugs in DirectProxies.js 1. Properties created via assignment gets `false' value for descriptor attributes; should be true. E.g. foo.bar = 10, where `foo' is direct proxy, makes bar non-configurable 2. Can't return descriptor with `configurable: false' for non-existing property; get: cannot report a non-configurable descriptor for non-existent property But we need it in case virtual methods Dmitry. ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: noSuchMethod: funargs + invoke-only-phantoms
On 17.12.2011 9:56, Andrea Giammarchi wrote: if both V8 and SpiderMonkey will follow that logic to trap invoke-only method, I'll do my best to promote and explain how it works and why addressing anyhow does not make sense since there is nothing to address being inexistent. It was my main thoughts and arguments through that never-ending initial thread. And this position of course makes perfect sense. However, it may also be broken until we don't have the answer to the following question: Why does a programmer have an error in the following transformation of a code? Was: lib.toRussianName(Andrea); // ?? Became: var toRussianName = lib.toRussianName; toRussianName.apply(null, [Andrea, Alex]); // error, toRussianName is undefined If you can explain it to the programmer that she should first go to the documentation and to see that methods such as `toCountryName' are virtual, but not real and then to use all such cases with caution, then this is OK. This is actually the only way to solve this issue -- to tell the programmer go to the documentation and check which virtual, i.e. invoke-only methods you have. In other case, you can't explain to her why she, being in JS, can't transform this line of a code into the second one. Can she do this? Does she have rights/license for this? Of course she can, of course she does. But in all other broken cases -- I already said, I agree that this implementation also breaks some logic. And in the same manner you'll have to explain to the programmer why if she: delete lib.toRussianName; then it still: typeof lib.toRussianName; // function, Trollface ;D So, the only answer on this topic is should be the answer on what is less painful and less critical in this case? To explain one broken invariants or others? Once we have answered this question, we may easily implement any from this design decisions. Dmitry. That case would be covered eventually by no such property but this one specially is trivial with Proxies, the method isn't. Te shouting is me being lazy with bold and stars trying to underlying common misconception I have read around about what problem noSuchMethod should bring, in my opinion non of them as long as the behavior is well defined and clear which is, to me, the case since ever. Good to know that at least SpiderMonkey is not planning to drop it Best Regards On Fri, Dec 16, 2011 at 5:59 PM, Brendan Eich bren...@mozilla.com mailto:bren...@mozilla.com wrote: I don't think SHOUTING helps your argument. The key point is whether and how any user of an abstraction can know that a given method is first- or second-class. Some frameworks such as TIBET use second-class methods only. Others (E4X, ECMA-357 comes to mind -- users did and do trip over its invoke-only methods) could segregate and document methods as to which can be extracted and called later with an appropriate |this|, and which are invoke-only. But arguing your conclusion that __noSuchMethod__ is only about the latter case of NOT HAVING A FUNCTION doesn't help. It's a circular argument. Abstractions of the O-O varieties have different philosophies about methods, but when applied to JS, the cross-browser libraries do not say you have to know if this method is real or virtual. People have not built much on __noSuchMethod__ since it's only in SpiderMonkey. We lack experience in-the-large with it. On this basis, I'm still happy to see method-missing traps implementable on top of direct proxies. Users will soon be able to experiment with such libraries in SpiderMonkey and V8. Then we can see what we've learned. If you are right, it'll be trivial to standardize one of these libraries, or even make a private-named unstratified noSuchMethod trap. /be - Original Message - From: Andrea Giammarchi andrea.giammar...@gmail.com mailto:andrea.giammar...@gmail.com To: Dmitry Soshnikov dmitry.soshni...@gmail.com mailto:dmitry.soshni...@gmail.com Cc: Brendan Eich bren...@mozilla.com mailto:bren...@mozilla.com, es-discuss es-discuss@mozilla.org mailto:es-discuss@mozilla.org Sent: Friday, December 16, 2011 8:30:47 AM Subject: Re: noSuchMethod: funargs + invoke-only-phantoms you don't use apply randomly, you use apply for methods or getters knowing there is a function there. __noSuchMethod__ is about NOT HAVING A FUNCTION there and if the property is not defined apply should fail as well as obj.undefined.apply would I still do not understand why we keep mixing up getters with __noSuchMethod__ behavior which is: 1. a method and not a property invocation ( no obj.inexistent.apply BUT ONLY obj.inexistent() OR obj[inexistent]() ) 2. unaddressable since a property that has not been define will always be addressed as undefined ( or the __proto__ chain value ) 3. nothing to defer
Re: noSuchMethod: funargs + invoke-only-phantoms
Hello, from my point the scenario that: delete lib.toRussianName; then it still: typeof lib.toRussianName; // function, Trollface ;D is much more acceptable (it happens everyday - there are non-writable properties everywhere), than the scenario where I cannot transform lib.toRussianName(Andrea); // Андрей into var toRussianName = lib.toRussianName; toRussianName.apply(null, [Andrea, Alex]); // error, toRussianName is undefined That's why I proposed first-class phantoms in gist: beasts that typeof to phantom, ToBoolean to false, ToNumber to 0, are wrapping a function, [[Call]] calls that function, [[Get]] and [[Prototype]] delegates to that function ([[Class]] is questionable) and rest does not work ([[Set]] silently fails etc.). And the ability to return them from any code, not just proxies. Dmitry. Herby ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: noSuchMethod: funargs + invoke-only-phantoms
Dmitry, addressing a trap fallback is not a good idea plus the average JS
coder rarely does it ... said that, the moment you are using a method you
already know this exists so you already know the documentation ( or part of
it ) so I don't see much hurt there.
Moreover, the addressing problem is common for all self bound methods and
the usage of call and apply
var o {getStuff:function(){return o.stuff}};
// or o.getStuff = o.getStuff.bind(o);
Whoever gonna address getStuff will have unexpected results with any
context different from o so, again, whoever is using a method must know at
least basis of the methods.
Methods that fallbacks through a trap as noSuchMethod is should not be
documented as methods because inexistent, these should rather be documented
under the magic behavior explaining in the very first how it works and
why.
I don't see many troubles into an invoke-only fallback, I see troubles or
limits without this possibility.
The proxy trap is not even an option to me, not to simulate proper
noSuchMethod behavior where again, typeof o.nonExistentMethod should be
undefined, accordingly with __proto__ and getter over that property.
Are these missing? Cool, there is no such method or property with that name
so undefined and nothing else.
Ideally, we could find a better way to define objects that implements
__noSuchMethod__ interface so that developers can be aware in advance of
potential mistakes
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Re: noSuchMethod: funargs + invoke-only-phantoms
and about last point, maybe objects that implements noSuchMethod should
return something like unknown via typeof ... just saying, and simply to
differentiate these objects from others where __noSuchMethod__ is not in
place.
On Sat, Dec 17, 2011 at 3:08 PM, Andrea Giammarchi
andrea.giammar...@gmail.com wrote:
Dmitry, addressing a trap fallback is not a good idea plus the average JS
coder rarely does it ... said that, the moment you are using a method you
already know this exists so you already know the documentation ( or part of
it ) so I don't see much hurt there.
Moreover, the addressing problem is common for all self bound methods and
the usage of call and apply
var o {getStuff:function(){return o.stuff}};
// or o.getStuff = o.getStuff.bind(o);
Whoever gonna address getStuff will have unexpected results with any
context different from o so, again, whoever is using a method must know at
least basis of the methods.
Methods that fallbacks through a trap as noSuchMethod is should not be
documented as methods because inexistent, these should rather be documented
under the magic behavior explaining in the very first how it works and
why.
I don't see many troubles into an invoke-only fallback, I see troubles or
limits without this possibility.
The proxy trap is not even an option to me, not to simulate proper
noSuchMethod behavior where again, typeof o.nonExistentMethod should be
undefined, accordingly with __proto__ and getter over that property.
Are these missing? Cool, there is no such method or property with that
name so undefined and nothing else.
Ideally, we could find a better way to define objects that implements
__noSuchMethod__ interface so that developers can be aware in advance of
potential mistakes
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Re: noSuchMethod: funargs + invoke-only-phantoms
On 17.12.2011 17:21, Herby Vojčík wrote: Hello, from my point the scenario that: delete lib.toRussianName; then it still: typeof lib.toRussianName; // function, Trollface ;D is much more acceptable (it happens everyday - there are non-writable properties everywhere), Yes, good point on non-configurable properties. So, we may justify this broken invariant with `delete' which becomes not so broken. it's good. Agreed. than the scenario where I cannot transform lib.toRussianName(Andrea); // Андрей into var toRussianName = lib.toRussianName; toRussianName.apply(null, [Andrea, Alex]); // error, toRussianName is undefined That's why I proposed first-class phantoms in gist: beasts that typeof to phantom, ToBoolean to false, ToNumber to 0, are wrapping a function, [[Call]] calls that function, [[Get]] and [[Prototype]] delegates to that function ([[Class]] is questionable) and rest does not work ([[Set]] silently fails etc.). And the ability to return them from any code, not just proxies. This is by the way, may also be an interesting idea. You mean phantom is the function returned from `get' or it for non-existing method in case of noSuchMethod is used? Dmitry. ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: noSuchMethod: funargs + invoke-only-phantoms
On 17.12.2011 18:08, Andrea Giammarchi wrote:
Dmitry, addressing a trap fallback is not a good idea plus the average
JS coder rarely does it ... said that, the moment you are using a
method you already know this exists so you already know the
documentation ( or part of it ) so I don't see much hurt there.
That's it. In designing a language it's better not to build the
decisions based on rarely reasons. Yes, of course we should consider
percentage of usage of this or that feature, so basically it's good to
analyze whether is feature is rare or frequent. But in general, we
can't predict 100% will the method be used in some different ways or not
-- especially if the user _may_ use it in this way in JS.
Once again, in PHP and others it's much easier to implement things like
`__call', etc (until 5.3 it even didn't have closures). In languages
like Ruby it's also easier to implement it, since `foo.bar' is _already
a method call_ (or sending a message). There is only method calls in
Ruby, there are no properties. This is why `method_missing' is logical
there.
In JS, as well as in Python, there is no method calls, but there is
getting property values and already after that provide some operations
on them (in case if the value of the property is a function, you may
call it). This is, by the way, why Python also doesn't support separated
`__nomethod__' magic name. In Python, as well as in JS proxies, you have
to return an activator function from `__getattr__'.
Moreover, the addressing problem is common for all self bound methods
and the usage of call and apply
var o {getStuff:function(){return o.stuff}};
// or o.getStuff = o.getStuff.bind(o);
Whoever gonna address getStuff will have unexpected results with any
context different from o so, again, whoever is using a method must
know at least basis of the methods.
Yes, this is fair enough. If the user extracts the function for further
applies, she should know whether a function is generic to be able apply
it for different `this' values. OTOH, she can do this only for
optimizations. `toString.call' is faster than
`Object.prototype.toString.call', so she just saves it to the variable
and calls.
Methods that fallbacks through a trap as noSuchMethod is should not be
documented as methods because inexistent, these should rather be
documented under the magic behavior explaining in the very first how
it works and why.
Yes, as I said, I see this way as the only existing to solve the issue
-- to mention in the documentation, that methods such as
`find_by_fieldName' are magic and that we can't extract them or apply
in different contexts. If this is acceptable, then this is OK. Then we
force user to know it and to follow this rule. OTOH, it may be good.
I don't see many troubles into an invoke-only fallback, I see troubles
or limits without this possibility.
The proxy trap is not even an option to me, not to simulate proper
noSuchMethod behavior where again, typeof o.nonExistentMethod should
be undefined, accordingly with __proto__ and getter over that property.
Yep, this is also true, and I mentioned it several times in that long
thread.
Are these missing? Cool, there is no such method or property with that
name so undefined and nothing else.
Ideally, we could find a better way to define objects that implements
__noSuchMethod__ interface so that developers can be aware in advance
of potential mistakes
This is what nearly Tom proposes with inheriting a special (proxy)
object. I.e. some object which inherit it will have this _unstratified_
noSuchMethod, placed directly on the object (still via proxies, with all
broken invariants applied), and some do not. OTOH, he also proposed to
be `Object.prototype' as such a proxy. It can be a good idea, though
will decrease efficiency.
Dmitry.
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Re: noSuchMethod: funargs + invoke-only-phantoms
That's why I proposed first-class phantoms in gist: beasts that typeof to phantom, ToBoolean to false, ToNumber to 0, are wrapping a function, [[Call]] calls that function, [[Get]] and [[Prototype]] delegates to that function ([[Class]] is questionable) and rest does not work ([[Set]] silently fails etc.). And the ability to return them from any code, not just proxies. This is by the way, may also be an interesting idea. You mean phantom is the function returned from `get' or it for non-existing method in case of noSuchMethod is used? Returned from `get'. Or wherever else, too, if you feel, but get trap of a proxy is one of the obvious uses. Dmitry. Herby ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: noSuchMethod: funargs + invoke-only-phantoms
From: Dmitry Soshnikov dmitry.soshni...@gmail.com On 17.12.2011 17:21, Herby Vojčík wrote: Hello, from my point the scenario that: delete lib.toRussianName; then it still: typeof lib.toRussianName; // function, Trollface ;D is much more acceptable (it happens everyday - there are non-writable properties everywhere), Yes, good point on non-configurable properties. So, we may justify this broken invariant with `delete' which becomes not so broken. it's good. Not so fast: the result of the delete expression differs in the non-configurable case (false) from the no-such-property case (true). /be ___ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
Re: noSuchMethod: funargs + invoke-only-phantoms
Yep, no doubt, first-class missed methods win -- again, because the programmer can and has the complete right (by just looking at one line of a code) to rewrite simple invoke to `apply' (she don't have to think whether it's a virtual method or not). The only thing I wanted is to reduce broken consequences. Well, or at least to be aware about them ;) Dmitry. On Thu, Dec 15, 2011 at 9:32 PM, Brendan Eich bren...@mozilla.com wrote: Agreed there are use-cases for second-class methods, according to style and taste. The impetus for __noSuchMethod__ when I implemented it in 2003 was to support the Smalltalk-based TIBET framework of Bill Edney and Scott Shattuck. They religiously use a Smalltalk style of JS so do not feel any second-class pain. Other styles of JS would definitely feel pain. One size does not fit all. This is why rejecting an invoke trap is not a matter of black and white, IMHO -- it's simply a desire to reduce complexity and see how the result can be used by a library (a standard one, even) to implement something like __noSuchMethod__. /be - Original Message - From: Dmitry Soshnikov dmitry.soshni...@gmail.com To: es-discuss es-discuss@mozilla.org Sent: Thursday, December 15, 2011 5:48:37 AM Subject: noSuchMethod: funargs + invoke-only-phantoms Hi, Here is the analysis of current noSuchMethod situation implemented via proxies. I summarized that never-ending thread from 2010 ( https://mail.mozilla.org/pipermail/es-discuss/2010-October/011929.html ), since guys in JS community started to ask why proxies don't support noSuchMethod. It's written as a small article in a view of JS-code: https://gist.github.com/1481018 Is there something to add? To change probably in the current Tom's proposal? Etc. P.S.: while I was writing the article, I started more to agree on importance of the extracted funargs in this case, however the invoke-only-phantom methods still and also (as it turns out) are needed to users and required by them. Cheers, Dmitry. ___ 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
Re: noSuchMethod: funargs + invoke-only-phantoms
you don't use apply randomly, you use apply for methods or getters knowing
there is a function there.
__noSuchMethod__ is about NOT HAVING A FUNCTION there and if the property
is not defined apply should fail as well as obj.undefined.apply would
I still do not understand why we keep mixing up getters with
__noSuchMethod__ behavior which is:
1. a method and not a property invocation ( no obj.inexistent.apply
BUT ONLY obj.inexistent() OR obj[inexistent]() )
2. unaddressable since a property that has not been define will always
be addressed as undefined ( or the __proto__ chain value )
3. nothing to defer, lazy call, pass through, etc etc ... once again,
noSuchMethod SHOULD cover 1 case, and 1 case only
obj.iDoNotExistHowCanAnyoneReferAtMeThen();
Rules behind the scene, described already in my post:
Syntax: object.methodName(); // inline invokaction, NO EXCEPTIONS TO THIS
SINGLE CASE
Procedure:
1. check if object has a property called methodName
1.1 yes, go on and throw an error if it is not callable
1.2 no, check if the property has a getter
1.2.1 yes, go on and throw an error if it is not callable
1.2.2 no, check if the object has a __noSuchMethod__ fallback
1.2.2.1 yes, invoke that callback via cb.call(object,
__noSuchMethod__, arguments)
1.2.2.2 no, throw an error undefined is not a method
Is above logic really that hard to implement/understand? I don't think so
but it looks like it's me only.
The described behavior as it is is never ambiguous so what is the problem
exactly?
Practical example
var o = Object.defineProperty({}, test, {
get: function () {
return this.alias;
}
});
o.alias = function () {
alert(this.message);
};
o.message = hello;
o.toString();// __proto__ chain
o.alias(); // property as method
o.test();// getter
o.noTest(); // __noSuchMethod__
o.test.call(o); // getter
o.noTest.call(o);// undefined is not a function
Best Regards
On Fri, Dec 16, 2011 at 9:54 AM, Dmitry Soshnikov
dmitry.soshni...@gmail.com wrote:
Yep, no doubt, first-class missed methods win -- again, because the
programmer can and has the complete right (by just looking at one line of a
code) to rewrite simple invoke to `apply' (she don't have to think whether
it's a virtual method or not).
The only thing I wanted is to reduce broken consequences. Well, or at
least to be aware about them ;)
Dmitry.
On Thu, Dec 15, 2011 at 9:32 PM, Brendan Eich bren...@mozilla.com wrote:
Agreed there are use-cases for second-class methods, according to style
and taste.
The impetus for __noSuchMethod__ when I implemented it in 2003 was to
support the Smalltalk-based TIBET framework of Bill Edney and Scott
Shattuck. They religiously use a Smalltalk style of JS so do not feel any
second-class pain.
Other styles of JS would definitely feel pain. One size does not fit all.
This is why rejecting an invoke trap is not a matter of black and white,
IMHO -- it's simply a desire to reduce complexity and see how the result
can be used by a library (a standard one, even) to implement something like
__noSuchMethod__.
/be
- Original Message -
From: Dmitry Soshnikov dmitry.soshni...@gmail.com
To: es-discuss es-discuss@mozilla.org
Sent: Thursday, December 15, 2011 5:48:37 AM
Subject: noSuchMethod: funargs + invoke-only-phantoms
Hi,
Here is the analysis of current noSuchMethod situation implemented via
proxies.
I summarized that never-ending thread from 2010 (
https://mail.mozilla.org/pipermail/es-discuss/2010-October/011929.html),
since guys in JS community started to ask why proxies don't support
noSuchMethod.
It's written as a small article in a view of JS-code:
https://gist.github.com/1481018
Is there something to add? To change probably in the current Tom's
proposal? Etc.
P.S.: while I was writing the article, I started more to agree on
importance of the extracted funargs in this case, however the
invoke-only-phantom methods still and also (as it turns out) are needed
to users and required by them.
Cheers,
Dmitry.
___
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
Re: noSuchMethod: funargs + invoke-only-phantoms
sorry for the typo, this point was
1.2.2.1 yes, invoke that callback via cb.call(object, *methodName*,
arguments)
On Fri, Dec 16, 2011 at 5:30 PM, Andrea Giammarchi
andrea.giammar...@gmail.com wrote:
you don't use apply randomly, you use apply for methods or getters knowing
there is a function there.
__noSuchMethod__ is about NOT HAVING A FUNCTION there and if the property
is not defined apply should fail as well as obj.undefined.apply would
I still do not understand why we keep mixing up getters with
__noSuchMethod__ behavior which is:
1. a method and not a property invocation ( no obj.inexistent.apply
BUT ONLY obj.inexistent() OR obj[inexistent]() )
2. unaddressable since a property that has not been define will always
be addressed as undefined ( or the __proto__ chain value )
3. nothing to defer, lazy call, pass through, etc etc ... once again,
noSuchMethod SHOULD cover 1 case, and 1 case only
obj.iDoNotExistHowCanAnyoneReferAtMeThen();
Rules behind the scene, described already in my post:
Syntax: object.methodName(); // inline invokaction, NO EXCEPTIONS TO THIS
SINGLE CASE
Procedure:
1. check if object has a property called methodName
1.1 yes, go on and throw an error if it is not callable
1.2 no, check if the property has a getter
1.2.1 yes, go on and throw an error if it is not callable
1.2.2 no, check if the object has a __noSuchMethod__ fallback
1.2.2.1 yes, invoke that callback via cb.call(object,
__noSuchMethod__, arguments)
1.2.2.2 no, throw an error undefined is not a method
Is above logic really that hard to implement/understand? I don't think so
but it looks like it's me only.
The described behavior as it is is never ambiguous so what is the problem
exactly?
Practical example
var o = Object.defineProperty({}, test, {
get: function () {
return this.alias;
}
});
o.alias = function () {
alert(this.message);
};
o.message = hello;
o.toString();// __proto__ chain
o.alias(); // property as method
o.test();// getter
o.noTest(); // __noSuchMethod__
o.test.call(o); // getter
o.noTest.call(o);// undefined is not a function
Best Regards
On Fri, Dec 16, 2011 at 9:54 AM, Dmitry Soshnikov
dmitry.soshni...@gmail.com wrote:
Yep, no doubt, first-class missed methods win -- again, because the
programmer can and has the complete right (by just looking at one line of a
code) to rewrite simple invoke to `apply' (she don't have to think whether
it's a virtual method or not).
The only thing I wanted is to reduce broken consequences. Well, or at
least to be aware about them ;)
Dmitry.
On Thu, Dec 15, 2011 at 9:32 PM, Brendan Eich bren...@mozilla.comwrote:
Agreed there are use-cases for second-class methods, according to style
and taste.
The impetus for __noSuchMethod__ when I implemented it in 2003 was to
support the Smalltalk-based TIBET framework of Bill Edney and Scott
Shattuck. They religiously use a Smalltalk style of JS so do not feel any
second-class pain.
Other styles of JS would definitely feel pain. One size does not fit all.
This is why rejecting an invoke trap is not a matter of black and white,
IMHO -- it's simply a desire to reduce complexity and see how the result
can be used by a library (a standard one, even) to implement something like
__noSuchMethod__.
/be
- Original Message -
From: Dmitry Soshnikov dmitry.soshni...@gmail.com
To: es-discuss es-discuss@mozilla.org
Sent: Thursday, December 15, 2011 5:48:37 AM
Subject: noSuchMethod: funargs + invoke-only-phantoms
Hi,
Here is the analysis of current noSuchMethod situation implemented via
proxies.
I summarized that never-ending thread from 2010 (
https://mail.mozilla.org/pipermail/es-discuss/2010-October/011929.html),
since guys in JS community started to ask why proxies don't support
noSuchMethod.
It's written as a small article in a view of JS-code:
https://gist.github.com/1481018
Is there something to add? To change probably in the current Tom's
proposal? Etc.
P.S.: while I was writing the article, I started more to agree on
importance of the extracted funargs in this case, however the
invoke-only-phantom methods still and also (as it turns out) are needed
to users and required by them.
Cheers,
Dmitry.
___
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
Re: noSuchMethod: funargs + invoke-only-phantoms
I don't think SHOUTING helps your argument.
The key point is whether and how any user of an abstraction can know that a
given method is first- or second-class. Some frameworks such as TIBET use
second-class methods only.
Others (E4X, ECMA-357 comes to mind -- users did and do trip over its
invoke-only methods) could segregate and document methods as to which can be
extracted and called later with an appropriate |this|, and which are
invoke-only.
But arguing your conclusion that __noSuchMethod__ is only about the latter case
of NOT HAVING A FUNCTION doesn't help. It's a circular argument.
Abstractions of the O-O varieties have different philosophies about methods,
but when applied to JS, the cross-browser libraries do not say you have to
know if this method is real or virtual. People have not built much on
__noSuchMethod__ since it's only in SpiderMonkey. We lack experience
in-the-large with it.
On this basis, I'm still happy to see method-missing traps implementable on top
of direct proxies. Users will soon be able to experiment with such libraries in
SpiderMonkey and V8. Then we can see what we've learned. If you are right,
it'll be trivial to standardize one of these libraries, or even make a
private-named unstratified noSuchMethod trap.
/be
- Original Message -
From: Andrea Giammarchi andrea.giammar...@gmail.com
To: Dmitry Soshnikov dmitry.soshni...@gmail.com
Cc: Brendan Eich bren...@mozilla.com, es-discuss es-discuss@mozilla.org
Sent: Friday, December 16, 2011 8:30:47 AM
Subject: Re: noSuchMethod: funargs + invoke-only-phantoms
you don't use apply randomly, you use apply for methods or getters knowing
there is a function there.
__noSuchMethod__ is about NOT HAVING A FUNCTION there and if the property is
not defined apply should fail as well as obj.undefined.apply would
I still do not understand why we keep mixing up getters with __noSuchMethod__
behavior which is:
1. a method and not a property invocation ( no obj.inexistent.apply BUT ONLY
obj.inexistent() OR obj[inexistent]() )
2. unaddressable since a property that has not been define will always be
addressed as undefined ( or the __proto__ chain value )
3. nothing to defer, lazy call, pass through, etc etc ... once again,
noSuchMethod SHOULD cover 1 case, and 1 case only
obj.iDoNotExistHowCanAnyoneReferAtMeThen();
Rules behind the scene, described already in my post:
Syntax: object.methodName(); // inline invokaction, NO EXCEPTIONS TO THIS
SINGLE CASE
Procedure:
1. check if object has a property called methodName
1.1 yes, go on and throw an error if it is not callable
1.2 no, check if the property has a getter
1.2.1 yes, go on and throw an error if it is not callable
1.2.2 no, check if the object has a __noSuchMethod__ fallback
1.2.2.1 yes, invoke that callback via cb.call(object, __noSuchMethod__,
arguments)
1.2.2.2 no, throw an error undefined is not a method
Is above logic really that hard to implement/understand? I don't think so but
it looks like it's me only.
The described behavior as it is is never ambiguous so what is the problem
exactly?
Practical example
var o = Object.defineProperty({}, test, {
get: function () {
return this.alias;
}
});
o.alias = function () {
alert(this.message);
};
o.message = hello;
o.toString(); // __proto__ chain
o.alias(); // property as method
o.test(); // getter
o.noTest(); // __noSuchMethod__
o.test.call(o); // getter
o.noTest.call(o);// undefined is not a function
Best Regards
On Fri, Dec 16, 2011 at 9:54 AM, Dmitry Soshnikov dmitry.soshni...@gmail.com
wrote:
Yep, no doubt, first-class missed methods win -- again, because the
programmer can and has the complete right (by just looking at one line of a
code) to rewrite simple invoke to `apply' (she don't have to think whether it's
a virtual method or not).
The only thing I wanted is to reduce broken consequences. Well, or at least to
be aware about them ;)
Dmitry.
On Thu, Dec 15, 2011 at 9:32 PM, Brendan Eich bren...@mozilla.com wrote:
Agreed there are use-cases for second-class methods, according to style and
taste.
The impetus for __noSuchMethod__ when I implemented it in 2003 was to support
the Smalltalk-based TIBET framework of Bill Edney and Scott Shattuck. They
religiously use a Smalltalk style of JS so do not feel any second-class pain.
Other styles of JS would definitely feel pain. One size does not fit all.
This is why rejecting an invoke trap is not a matter of black and white, IMHO
-- it's simply a desire to reduce complexity and see how the result can be used
by a library (a standard one, even) to implement something like
__noSuchMethod__.
/be
- Original Message -
From: Dmitry Soshnikov dmitry.soshni...@gmail.com
To: es-discuss es-discuss@mozilla.org
Sent: Thursday, December 15, 2011 5:48:37 AM
Subject: noSuchMethod: funargs + invoke-only-phantoms
Hi,
Here is the analysis of current
Re: noSuchMethod: funargs + invoke-only-phantoms
if both V8 and SpiderMonkey will follow that logic to trap invoke-only
method, I'll do my best to promote and explain how it works and why
addressing anyhow does not make sense since there is nothing to address
being inexistent.
That case would be covered eventually by no such property but this one
specially is trivial with Proxies, the method isn't.
Te shouting is me being lazy with bold and stars trying to underlying
common misconception I have read around about what problem noSuchMethod
should bring, in my opinion non of them as long as the behavior is well
defined and clear which is, to me, the case since ever.
Good to know that at least SpiderMonkey is not planning to drop it
Best Regards
On Fri, Dec 16, 2011 at 5:59 PM, Brendan Eich bren...@mozilla.com wrote:
I don't think SHOUTING helps your argument.
The key point is whether and how any user of an abstraction can know that
a given method is first- or second-class. Some frameworks such as TIBET use
second-class methods only.
Others (E4X, ECMA-357 comes to mind -- users did and do trip over its
invoke-only methods) could segregate and document methods as to which can
be extracted and called later with an appropriate |this|, and which are
invoke-only.
But arguing your conclusion that __noSuchMethod__ is only about the latter
case of NOT HAVING A FUNCTION doesn't help. It's a circular argument.
Abstractions of the O-O varieties have different philosophies about
methods, but when applied to JS, the cross-browser libraries do not say
you have to know if this method is real or virtual. People have not built
much on __noSuchMethod__ since it's only in SpiderMonkey. We lack
experience in-the-large with it.
On this basis, I'm still happy to see method-missing traps implementable
on top of direct proxies. Users will soon be able to experiment with such
libraries in SpiderMonkey and V8. Then we can see what we've learned. If
you are right, it'll be trivial to standardize one of these libraries, or
even make a private-named unstratified noSuchMethod trap.
/be
- Original Message -
From: Andrea Giammarchi andrea.giammar...@gmail.com
To: Dmitry Soshnikov dmitry.soshni...@gmail.com
Cc: Brendan Eich bren...@mozilla.com, es-discuss
es-discuss@mozilla.org
Sent: Friday, December 16, 2011 8:30:47 AM
Subject: Re: noSuchMethod: funargs + invoke-only-phantoms
you don't use apply randomly, you use apply for methods or getters knowing
there is a function there.
__noSuchMethod__ is about NOT HAVING A FUNCTION there and if the property
is not defined apply should fail as well as obj.undefined.apply would
I still do not understand why we keep mixing up getters with
__noSuchMethod__ behavior which is:
1. a method and not a property invocation ( no obj.inexistent.apply BUT
ONLY obj.inexistent() OR obj[inexistent]() )
2. unaddressable since a property that has not been define will always be
addressed as undefined ( or the __proto__ chain value )
3. nothing to defer, lazy call, pass through, etc etc ... once again,
noSuchMethod SHOULD cover 1 case, and 1 case only
obj.iDoNotExistHowCanAnyoneReferAtMeThen();
Rules behind the scene, described already in my post:
Syntax: object.methodName(); // inline invokaction, NO EXCEPTIONS TO THIS
SINGLE CASE
Procedure:
1. check if object has a property called methodName
1.1 yes, go on and throw an error if it is not callable
1.2 no, check if the property has a getter
1.2.1 yes, go on and throw an error if it is not callable
1.2.2 no, check if the object has a __noSuchMethod__ fallback
1.2.2.1 yes, invoke that callback via cb.call(object, __noSuchMethod__,
arguments)
1.2.2.2 no, throw an error undefined is not a method
Is above logic really that hard to implement/understand? I don't think so
but it looks like it's me only.
The described behavior as it is is never ambiguous so what is the problem
exactly?
Practical example
var o = Object.defineProperty({}, test, {
get: function () {
return this.alias;
}
});
o.alias = function () {
alert(this.message);
};
o.message = hello;
o.toString(); // __proto__ chain
o.alias(); // property as method
o.test(); // getter
o.noTest(); // __noSuchMethod__
o.test.call(o); // getter
o.noTest.call(o);// undefined is not a function
Best Regards
On Fri, Dec 16, 2011 at 9:54 AM, Dmitry Soshnikov
dmitry.soshni...@gmail.com wrote:
Yep, no doubt, first-class missed methods win -- again, because the
programmer can and has the complete right (by just looking at one line of a
code) to rewrite simple invoke to `apply' (she don't have to think whether
it's a virtual method or not).
The only thing I wanted is to reduce broken consequences. Well, or at
least to be aware about them ;)
Dmitry.
On Thu, Dec 15, 2011 at 9:32 PM, Brendan Eich bren...@mozilla.com
wrote:
Agreed there are use-cases for second-class methods, according to style
and taste.
The impetus for __noSuchMethod__
