feat: hide allocator functions when unusable

[cooronx]

issue #725

when no allocator feature is enabled, hide them from public API

[alejandro-vaz]

it works but I don't think this is the way

I was thinking more of having conditional visibility based on attributes

something similar to what the add-syntax crate does but just about visibility

[cooronx]

I found a crate called visibility, seems to meet our requirements
it works like this

#[cfg_attr(
    any(feature = "feature_a", feature = "feature_b"),
    visibility::make(pub)
)]
fn test_fn() {
    println!("hello");
}

https://crates.io/crates/visibility

https://github.com/danielhenrymantilla/visibility.rs

[alejandro-vaz]

yeah but we can't add the crate as dependency

this is smallvec, each dependency is a potential risk, and depending on small crates with an unknown dependency graph is extremely risky for the ecosystem

whatever we do, it has to be self-hosted

[cooronx]

i think we can write our own proc-marco, do the same thing as visibility does. not sure if this is the way you mean it.

[alejandro-vaz]

yeah I think that's the way

[alejandro-vaz]

wait wait wait let's think through it again

I don't like the idea we have another crate to publish

[alejandro-vaz]

don't we have any way to do the same thing without having a completely new crate to publish??

[cooronx]

hi, I've updated the PR to implement the proc-macro we discussed — it works, and there are no external dependencies. but proc macros have to live in their own crate, That feels like a lot of overhead for something small.

[cooronx]

wait wait wait let's think through it again

I don't like the idea we have another crate to publish

I also find it quite odd, but I'm not sure how else to implement it.

[cooronx]

don't we have any way to do the same thing without having a completely new crate to publish??

maybe just back to the original approach instead, copy the api twice？

[alejandro-vaz]

I don't like copying things twice, it's just a bad practice

can we hack ourselves into it with a simple macro-rules macro that injects a pub keyword if an attribute is true??

like

macro_rules! public {
    ($attribute:meta) => {{
        #[cfg($attribute)]
        pub
    }}
}

or something weird like that, idk

[alejandro-vaz]

can be removed

[alejandro-vaz]

we can move this file to src/macros.rs and convert that file to a proc-macro crate itself and then take the normal smallvec crate and re-export all those macros

[alejandro-vaz]

now that I think about it, this means we have to publish a new crate

I don't like that idea

[alejandro-vaz]

the only thing I don't like about this approach is that processing the token stream disables IDE help

[cooronx]

the only thing I don't like about this approach is that processing the token stream disables IDE help

tried it on my vscode + rust-analyzer (0.3.3073) and completion works fine inside public!, not sure about other IDEs. rustfmt is a real problem though — it just won't format anything inside the macro invocation.

[alejandro-vaz]

fuck me, give me some time to think about it and we'll see what we do

[alejandro-vaz]

okay you there?? I have found the way

look at #764

I'll get that merged and then you can use it for this PR

it basically is a private procedural macro similar to add-syntax::prepend but self-hosted, and it doesn't need to be published to work

[cooronx]

okay you there?? I have found the way

look at #764

I'll get that merged and then you can use it for this PR

it basically is a private procedural macro similar to add-syntax::prepend but self-hosted, and it doesn't need to be published to work

got it, wait for #764 merged