"Module doesn't have export __wbindgen_describe___wbg_f_alert_alert_n"

[steveklabnik]

Code:

> cat .\src\lib.rs
#![feature(proc_macro, wasm_import_module, wasm_custom_section)]

extern crate wasm_bindgen;

use wasm_bindgen::prelude::*;

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

#[wasm_bindgen]
pub fn greet(name: &str) {
    alert(&format!("Hello, {}!", name));
}

Cargo.toml:

[package]
name = "wasmpacktest"
version = "0.1.0"
authors = ["steveklabnik <steve@steveklabnik.com>"]

[lib]
crate-type = ["cdylib"]

[dependencies]
wasm-bindgen = "0.2"

When I invoke wasm-bindgen through wasm-pack...:

> wasm-pack init

  [1/8] Checking crate configuration...
  [2/8] Adding WASM target...
  [3/8] Compiling to WASM...
  [4/8] Creating a pkg directory...
  [5/8] Writing a package.json...
  :-) [WARN]: Field description is missing from Cargo.toml. It is not necessary, but recommended
  :-) [WARN]: Field repository is missing from Cargo.toml. It is not necessary, but recommended
  :-) [WARN]: Field license is missing from Cargo.toml. It is not necessary, but recommended
  [6/8] Copying over your README...
  :-) [WARN]: origin crate has no README
  [7/8] Installing WASM-bindgen...
| [8/8] Running WASM-bindgen...
wasm-bindgen failed to execute properly. stderr:

thread 'main' panicked at 'failed to run export: Function("Module doesn\'t have export __wbindgen_describe___wbg_f_alert_alert_n")', libcore\result.rs:945:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.

rustc version:

> rustc --version
rustc 1.28.0-nightly (01cc982e9 2018-06-24)

Any ideas what's wrong here?

[wismer]

@steveklabnik I wonder if it has to do with the extern func declaration? I'm accustomed to seeing examples having the functions exposed with pub

[steveklabnik]

That is totally it! I've sent a docs PR upstream.

[fitzgen]

If the use of the thing is in the same crate (as is the case here), then it shouldn't need the pub... Not sure what is going on here.

[fitzgen]

I still think it is a bug that it doesn't work without pub.

[turboladen]

For future lurkers... I ran into this same thing where I was in business with:

// src/lib.rs
pub other_module;

// src/other_module.rs
#[wasm_bindgen]
// stuff

...but as soon as I removed the pub from the module declaration in lib.rs, I started getting the same as reported here. Had me scratching my head because all of the things in other_module were marked pub. Once I made made the module pub again I was 👍 .

[alexcrichton]

@turboladen I think that issue is #201

[alexcrichton]

@steveklabnik hm I'm a little confused and I wonder if this could be a roundabout version mismatch or wasm-pack bug? We have an example in this repository with your exact example above, and it's tested to work on CI

If you check out the master branch of this repo does the example work? Or does your installed tool work? Do you know what version was installed?

[turboladen]

Ah, thanks @alexcrichton !

[alexcrichton]

Hm I've also tried out the instructions in the OP and can't reproduce :(

[alexcrichton]

I'm gonna close this as this is likely a dupe of #201, but if not I can always reopen!