[quickjs-devel] Re: JS_CFUNC_DEF doesn't make properties enumerable
- From: Charlie Gordon <quickjs@xxxxxxxxxxx>
- To: Saúl Ibarra Corretgé <s@xxxxxxxxxx>
- Date: Tue, 6 Aug 2019 10:05:24 +0200
On 6 Aug 2019, at 09:28, Saúl Ibarra Corretgé <s@xxxxxxxxxx> wrote:
On 04/08/2019 20:13, Charlie Gordon wrote:
Hence there was no need for a more general macro to define these methods in
the static JSCFunctionListEntry tables.
But doesn't it make sense to have them when defining prototype functions
lists? Those should be enumerable, shouldn't they? At least so tab-tab
works on the REPL :-) Am I missing something?
In fact it does not, because it would make the class methods appear when
enumerating object properties in `for (x in obj)`. Imagine if you had to
distinguish between elements and methods when enumerating an Array?
Completion in the REPL does not rely on the “enumerable” property attribute,
but uses Object.getOwnPropertyNames and Object.getPrototypeOf to enumerate
object properties along the prototype chain, including methods. See function
get_completion() in repl.js for details. Given the choice made in the ECMA
Standard, we had to do it this way and it is actually quite simple.
You can write your own macros to define your own C based object properties,
but the implementation of these macros and the JSCFunctionListEntry
structure might change in the future so might need to change your macros to
work with newer versions of quickjs.
Yeah, I've done that, but indeed it looks "fragile". An "official" way
to do it would be most welcome.
Object.getOwnPropertyNames and Object.getPrototypeOf are not “fragile”, they
are one of the official ways to perform introspection. Enumerating properties
with `for (x in obj)` is considered obsolete, and `for (x of obj)` does not
follow the prototype chain, which is a relief considering the complexity of the
specification of `for (x in obj)`.
There seems to be little use for enumerable object methods. You can always
enumerate an object properties and its prototypes’ with Object methods.
Is the prototype methods for an object not a valid use case?
That’s arguable, but an explicit approach seems preferable over some form of
enumeration that mixes properties of different prototype objects in a single
list.
The ECMAScript specification is complex and convoluted enough already.
Consistency and simplicity should be sought whenever possible.
Thank for the feedback
Chqrlie.
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