rand panic when use wasm-bindgen

[uonr]

wasm-0000006e-415:2 Uncaught (in promise) RuntimeError: unreachable
    at __rust_start_panic (wasm-function[415]:1)
    at rust_panic (wasm-function[414]:30)
    at std::panicking::rust_panic_with_hook::hd20860d15108b702 (wasm-function[411]:444)
    at std::panicking::continue_panic_fmt::h5ff9aa1d01d30565 (wasm-function[410]:122)
    at std::panicking::begin_panic_fmt::h401167bbcd0103e3 (wasm-function[408]:95)
    at rand::rngs::thread::THREAD_RNG_KEY::__init::_$u7b$$u7b$closure$u7d$$u7d$::h8926014834b86cc9 (wasm-function[215]:204)
    at _$LT$core..result..Result$LT$T$C$$u20$E$GT$$GT$::unwrap_or_else::hd14d23538d2305a0 (wasm-function[87]:530)
    at rand::rngs::thread::THREAD_RNG_KEY::__init::h200f34f719285fc0 (wasm-function[214]:112)
    at _$LT$std..thread..local..LocalKey$LT$T$GT$$GT$::init::hd848dfe862f0da01 (wasm-function[80]:52)
    at _$LT$std..thread..local..LocalKey$LT$T$GT$$GT$::try_with::ha36a539a75cd6604 (wasm-function[82]:283)

simple code:

extern crate wasm_bindgen;
extern crate rand;
use wasm_bindgen::prelude::*;
// use rand::rngs::OsRng;

#[wasm_bindgen]
extern {
    fn alert(s: &str);
}

#[wasm_bindgen]
pub fn greet(name: &str) {
    // let _rng = OsRng::new();
    let value: i32 = rand::random();
    alert(&format!("Hello, {}!", value));
}

if use OsRng :

extern crate wasm_bindgen;
extern crate rand;
use wasm_bindgen::prelude::*;
use rand::rngs::OsRng;

#[wasm_bindgen]
extern {
    fn alert(s: &str);
}

#[wasm_bindgen]
pub fn greet(name: &str) {
    let _rng = OsRng::new();
    // let value: i32 = rand::random();
    alert(&format!("Hello, {}!", name));
}

can't found

error[E0432]: unresolved import `rand::rngs::OsRng`
 --> src/lib.rs:4:5
  |
4 | use rand::rngs::OsRng;
  |     ^^^^^^^^^^^^^^^^^ no `OsRng` in `rngs`

[uonr]

I've created a repo for reproduce this bug:
https://github.com/quanbrew/rust-wasm-rand-bug-reproduce

[dhardy]

From rngs/mod.rs:

#[cfg(all(feature="std",
          any(target_os = "linux", target_os = "android",
              target_os = "netbsd",
              target_os = "dragonfly",
              target_os = "haiku",
              target_os = "emscripten",
              target_os = "solaris",
              target_os = "cloudabi",
              target_os = "macos", target_os = "ios",
              target_os = "freebsd",
              target_os = "openbsd", target_os = "bitrig",
              target_os = "redox",
              target_os = "fuchsia",
              windows,
              all(target_arch = "wasm32", feature = "stdweb"),
              all(target_arch = "wasm32", feature = "wasm-bindgen"),
)))]
pub use self::os::OsRng;

You're using wasm32 with the wasm-bindgen feature?

[uonr]

the package `play` depends on `rand`, with features: `wasm-bindgen` but `rand` does not have these features.

Can't find "wasm-bindgen" feature in Cargo.toml https://github.com/rust-random/rand/blob/master/Cargo.toml

[upsuper]

It seems that rand on crates.io doesn't include wasm-bindgen yet. You need to use the git version instead.

[dhardy]

No, you'll have to wait for the 0.6 release for that #520

[coltfred]

We have successfully used rand's git master from wasm using wasm-bindgen. I'm working on helping with 0.6 so we can get that out ASAP.

[gregtatum]

Still not working for me on 0.6.1 or from specifying git master.

panicked at 'could not initialize thread_rng: No entropy sources available (permanently unavailable)', /.../.cargo/git/checkouts/rand-cc8f5b7ec2d3b6d9/2b5eac5/src/rngs/thread.rs:82:17

[dhardy]

@gregtatum since we're now on 0.6, I think it would be better to open a new issue; I think this one counts as "solved" now.

Could you include the error message from OsRng::new() in your report?