underscore at the start is no different that having a capital letter
It’s one character vs a bunch of ugly ones or a new whole file repeating half of what’s already written.
Regarding tooling…well, you can always put it in the compiler itself
Also the underscore already was a somewhat “compatible” meaning
But I agree, let’s not turn this into PHP but the question is… how simple would it be to make a tool for this?
do you know %%private? This seems not doable in ppx, it has to be done in the type checker
I actually still don’t understand what you mean 
Can you show a concrete code example of how it would be used? I mean an actual sample code, pretending that it exists right now. Correctness doesn’t matter, I just want to get an idea of what it is.
Take the example of bs-fetch.
The Fetch.ml is 430 lines and the Fetch.mli is more than half, 286.
Of course it helps to have a .resi to have a peek at the modules interface but if you really want to understand the inner workings if would be nice to have cleaner (no %%private) code with a simpler visual cue.
Of course, Js bindings, where almost everything is a signature, is an extreme case where you get a lot of code duplication and these are common in ReScript?
Also the fact that Rescript already gives names casing meaning wouldn’t make it so far fetched.
And it could work for filenames also.
I’m also developing some feelings for PHP dollar sign prefixes …not for this case though
Well…that’s the ugly thing I was talking about 
It’s a pitty ppx can’t handle that and I don’t want to go back to babel 
Worth noting that %%private reliably breaks editor tooling like types on hover in submodules.
I read all of this and I still don’t understand what you are asking for. So you don’t want to create a resi file. What kind of syntax do you want to use within a .res file that helps you skip the resi file?
Something like this?
@val
external _somePrivateThing: string = "someprivatething"
The declaration above would only be accessible within the module. Is this what you are talking about?
Exactly!! Is that stupid!? :-S
Even this:
let _myPrivateFunction = () => ....
And this:
_MyPrivateModule.res
Low all the way dash
Right now the _ prefix is used to explicitly mark a value as unused (otherwise the compiler will yield an unused-value warning).
IMO the language would need some proper public / private semantics and completely drop interface files… but that’s currently unrealistic for several reasons.
How is that supposed to work? How would you define which modules have access to MyPrivateModule? If you don’t want a module to be accessed, you could also do MyPrivateModule.foobar.res.
Right now the
_prefix is used to explicitly mark a value as unused (otherwise the compiler will yield an unused-value warning).
But that’s not a prefix is it?? Isn’t it the whole thing? If it’s unused you can have a single “_” and that’s wardly a prefix…otherwise I’ve been using a lot of unused variables
If you don’t want a module to be accessed, you could also do
MyPrivateModule.foobar.res
I don’t have a clue on what that does…wait…I got it, “Exotic Module Filenames”.
Hummm…I like MyPrivateModule better…I think
Something about "" beeing used for unused names that feels right to use for private names… where the user can’t use them
If you don’t want a module to be accessed, you could also do
MyPrivateModule.foobar.res.
This is a pretty ugly hack relying on some lexical conventions.
%%private is designed specifically for such use cases, when you want to expose most of them and hide only a very few utilities.
Worth noting that
%%privatereliably breaks editor tooling like types on hover in submodules
Then we should fix that
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Yeah but you’re already relying on uppercase words…
Another thing is that you also have a visual cue when you use them.
But again…that was just an idea to be used optionally with some tool not to be on the language itself.
I was just wondering if it would be a simple tool
Note most features can not be done in the syntactic level.
I am thinking maybe we can make the %%private more approachable by adopting a convention __ double underscore, so for double underscore started identifiers it is private by default, thoughts?
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making it configurable would be a can of worms right?
Is there really a underscore prefix already? Isn’t it just the single one for the unused var?
I guess a single one would break a lot of code but then again… it would be optional and also this is the right time to break stuff right?
Might be worth considering some alternatives. Not sure of implementation effort of these.
-
@privatedecorator feels consistent with other ReScript code. -
privatekeyword is common, including TypeScript. -
#varnameis JS syntax for class methods, but might add confusion with poly vars.
Underscore has been a convention in JS for private variables, so there is perhaps a case for it, but I’m personally not sure about making it a built in language feature.
A wild thought, in ReScript ' is a vaild char for identifier name. I wonder for identifier names ending with ', it is private.
For example:
let hello' = 3 // private
let hello = 3 // exported
Does it click with you?
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There was a previous discussion that discussed some ideas.
A comment from @Maxim
we could indeed add first class syntax support.
What do you think ofprivate let x = "foo"?
And you made a good point @Hongbo here:
I find
private letorlet privatealways more intuitive thanopen { .. }, the purpose is not to save some characters, it’s that people understandprivatewithout any further explanations which already appears in other languages like F# as mentioned above
Using ' is a nice simple syntax but I suspect it’s not intuitive.
It also might cause a surprise if anyone was not familiar with that syntax and used it as an alternative variable name. I understand in Haskell it’s an idiom to use x and x' and x'' meaning related but different variables.
I would say the underscore as a prefix for privacy is quite common in JS and TS, much more intuitive than a tick.
An explicit decorator or keyword is the best solution though IMO. It’s explicit, obvious, and without footguns.
Ideally I would want everything private by default and sprinkle %%public on bindings I want to expose (like Rust), but I get that this kind of breaking change may not be feasible. Given that, I prefer just having %%private (and fixing any issues that exist with it) instead of adding multiple ways to do something as critical as privacy.
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Technically, it’s a prefix. Any identifier starting with an underscore character can be unused without a compiler warning. This includes identifiers like _, _foo, _1, and so on.
I must have missed a lot of unused var messages by now
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I still think having interface file is one of the most powerful and useful feature of ocaml/rescript, you can check with one glance if a commit changes the API for example, how cool is that?
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