[js] enum-as-object cleanup wishlist

[nadako]

So I diffed the output with the new object-based enums and it looks great, however it increases code size in real-world cases quite a bit and I think we can do something about it:

enum E {
	A;
	B(v:Int);
}

generates

var E = { __ename__ : true, __constructs__ : ["A","B"] };
$hxEnums["E"] = E;
E.A = {_hx_index:0};
E.A.toString = $estr;
E.A.__enum__ = "E";
E.B = function(v) { var $x = {_hx_index:1,v:v,__enum__:"E"}; $x.toString = $estr; return $x; }
E.B.__params__ = ["v"];;

could be optimized to

var E = $hxEnums["E"] = { __ename__ : true, __constructs__ : ["A","B"] };
E.A = {_hx_index:0, toString: $estr, __enum__: "E"};
E.B = ($_ = function(v) { return {_hx_index:1,v:v,__enum__:"E",toString: $estr} }, $_.__params__ = ["v"], $_);

Basically we don't want to repat the type/ctor name too much because in real code it would be something like rambo_ResourceChangeReason.ClanwarAttackMaterialPurchase.

---

Another thing that makes me uncomfortable is the naming inconsistency here. We have _hx_index, but also __enum__ and $hxEnums. I feel like it would be better to use the $ident scheme for everything as this would also exclude the possibility of name clashes coming from weirdly-named identifiers in Haxe code.

So something like E.A = {$enum: "E", $index: 0, toString: $estr};. I think it would also look better when using the enum objects from plain JavaScript, as the $-fields look like special tag fields while non-$-fields contain data.

---

Thoughts?

[ncannasse]

Yes $ prefix is a better escaping sequence for JS output since it's not a valid Haxe identifier

[nadako]

Another thing - since we have $hxEnums now, it makes sense to make Type.resolveEnum use it instead of also putting enums into $hxClasses.

[nadako]

It's better now:

var E = $hxEnums["E"] = { __ename__ : true, __constructs__ : ["A","B"] };
E.A = {_hx_index:0,__enum__:"E",toString:$estr};
E.B = ($_=function(v) { return {_hx_index:1,v:v,__enum__:"E",toString:$estr}; },$_.__params__ = ["v"],$_);

still need to rename the fields ($enum and $index?)

another idea is to merge the declarations into one object, so we don't repeat the type name at all:

var E = {
  __constructs__: ["A", "B"],
  A: {$index: 0, $enum: "E"},
  B: ($_=function(v) { return {$index: 1, $enum: "E", v:v} },$_.__params__=["v"],$_),
}

[ncannasse]

$enum and $index is good for me. and yes the litteral declaration seems better

[Simn]

Do you still want to do something here for 4.0?

[nadako]

I wanted to unify impl fields to use $ instead of double underscores and _hx_ prefixes, but it's a bit annoying to implement because we want to access those fields from haxe code (Type.enumIndex etc). Not a priority for 4.0, I'd say.

[nadako]

I still think we should use $-prefixed fields, but it can't be done in a non-ugly way without #5105 or #9433 in place, because, as mentioned, we need to access them in the reflection API.

[nadako]

Also I don't like the fact that __enum__ is a string. IMO it should cycle-reference the enum definition object and the JSON round-trip argument seem weak to me (direct JSON.stringify on enums is not something anyone would want to do anyway).

So if there are no arguments against changing this, I'll do this at some point when I have time for it :)