Support for WASM without browser (wasm_bindgen)

[k0pernicus]

I was wondering if any support for WASM outside the browser (so, excluding wasm_bindgen from reqwest) is planned or not?

As an example, running this simple program on wasmtime does not work, regarding some components use wasm_bindgen to achieve some goals:

pub async fn fetch_data(url: &str) -> Result<String, reqwest::Error> {
    let client = reqwest::Client::new();
    let response = client.get(url).send().await?;
    response.text().await
}

#[tokio::main(flavor = "current_thread")]
async fn main() {
    fetch_data("https://www.google.com").await;
}

Compilation step:

cargo build --target="wasm32-wasip1"

Running step:

wasmtime target/wasm32-wasip1/debug/reqwest_wasi_test.wasm

thread 'main' panicked at /Users/antonin/.cargo/registry/src/index.crates.io-6f17d22bba15001f/js-sys-0.3.77/src/lib.rs:3441:1:
cannot call wasm-bindgen imported functions on non-wasm targets
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace
Error: failed to run main module target/wasm32-wasip1/debug/reqwest_wasi_test.wasm

The full log output:

Caused by:
    0: failed to invoke command default
    1: error while executing at wasm backtrace:
           0: 0x1760e5 - reqwest_wasi_test-b78f6a095419b422.wasm!__rust_start_panic
           1: 0x175ec6 - reqwest_wasi_test-b78f6a095419b422.wasm!rust_panic
           2: 0x175e02 - reqwest_wasi_test-b78f6a095419b422.wasm!std::panicking::rust_panic_with_hook::hcbca50d2f726c5b9
           3: 0x17501b - reqwest_wasi_test-b78f6a095419b422.wasm!std::panicking::begin_panic_handler::{{closure}}::hd5f594164b327db3
           4: 0x174f5a - reqwest_wasi_test-b78f6a095419b422.wasm!std::sys::backtrace::__rust_end_short_backtrace::h1dcad5b9bbce3e4b
           5: 0x17573e - reqwest_wasi_test-b78f6a095419b422.wasm!rust_begin_unwind
           6: 0x17fe04 - reqwest_wasi_test-b78f6a095419b422.wasm!core::panicking::panic_fmt::h0e15628bec7245b3
           7: 0x51429 - reqwest_wasi_test-b78f6a095419b422.wasm!js_sys::Object::new::__wbg_new_405e22f390576ce2::h07baa0578ae28fb4
           8: 0x5058f - reqwest_wasi_test-b78f6a095419b422.wasm!js_sys::Object::new::h92cdb7fa2c2c059b
           9: 0x4d011 - reqwest_wasi_test-b78f6a095419b422.wasm!web_sys::features::gen_RequestInit::RequestInit::new::hb315d70a8d03ee06
          10: 0x9484 - reqwest_wasi_test-b78f6a095419b422.wasm!reqwest::wasm::client::fetch::{{closure}}::hd1f7c3f3e07eb377
          11: 0x153ce - reqwest_wasi_test-b78f6a095419b422.wasm!reqwest::wasm::request::RequestBuilder::send::{{closure}}::hfbe6ac045409436e
          12: 0xc5e1 - reqwest_wasi_test-b78f6a095419b422.wasm!reqwest_wasi_test::fetch_data::{{closure}}::h95bc5d1465332d7e
          13: 0xcb69 - reqwest_wasi_test-b78f6a095419b422.wasm!reqwest_wasi_test::main::{{closure}}::h3c7599de9cb0c5c8
          14: 0xc39c - reqwest_wasi_test-b78f6a095419b422.wasm!<core::pin::Pin<P> as core::future::future::Future>::poll::h5a94842c7850d5b0
          15: 0x6890 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}::{{closure}}::{{closure}}::h822a08e5871a3356
          16: 0x5474 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}::{{closure}}::hf4428530e193b4aa
          17: 0x52ed - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::scheduler::current_thread::Context::enter::h9d2059f410c3916b
          18: 0x6412 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::scheduler::current_thread::CoreGuard::block_on::{{closure}}::h2c8db4f0698941fc
          19: 0x6283 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::scheduler::current_thread::CoreGuard::enter::{{closure}}::h60ec7de4102377f1
          20: 0x7225 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::context::scoped::Scoped<T>::set::h4b019683759bdfee
          21: 0x36cd - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::context::set_scheduler::{{closure}}::h1c3bef6d7c13badb
          22: 0xd818 - reqwest_wasi_test-b78f6a095419b422.wasm!std::thread::local::LocalKey<T>::try_with::h803f311836ccd027
          23: 0xd60b - reqwest_wasi_test-b78f6a095419b422.wasm!std::thread::local::LocalKey<T>::with::haf178bfffafaecee
          24: 0x35fe - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::context::set_scheduler::hbf7381da4acfc7f4
          25: 0x5bd5 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::scheduler::current_thread::CoreGuard::enter::h4afd3059c2e6e0ee
          26: 0x49d9 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::scheduler::current_thread::CoreGuard::block_on::h54c655a74657d586
          27: 0x46e6 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::scheduler::current_thread::CurrentThread::block_on::{{closure}}::h4cd71b623d2902ae
          28: 0x737e - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::context::runtime::enter_runtime::h10973758b664391e
          29: 0x3f24 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::scheduler::current_thread::CurrentThread::block_on::h6bb0b760c37c2c29
          30: 0x12978 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::runtime::Runtime::block_on_inner::h560ceb03fbd88de2
          31: 0x12a14 - reqwest_wasi_test-b78f6a095419b422.wasm!tokio::runtime::runtime::Runtime::block_on::ha8f0660e9646de76
          32: 0x9323 - reqwest_wasi_test-b78f6a095419b422.wasm!reqwest_wasi_test::main::hadf609d4e5abd2f9
          33: 0xe6f3 - reqwest_wasi_test-b78f6a095419b422.wasm!core::ops::function::FnOnce::call_once::hc5d798b5e9289b30
          34: 0xe2b8 - reqwest_wasi_test-b78f6a095419b422.wasm!std::sys::backtrace::__rust_begin_short_backtrace::hd7a74e6dcf9b902d
          35: 0xb22b - reqwest_wasi_test-b78f6a095419b422.wasm!std::rt::lang_start::{{closure}}::h7fc69762e5c0df08
          36: 0x173907 - reqwest_wasi_test-b78f6a095419b422.wasm!std::rt::lang_start_internal::ha2dbbf0137776456
          37: 0xb1c7 - reqwest_wasi_test-b78f6a095419b422.wasm!std::rt::lang_start::h72e8b69396a82c2e
          38: 0x938b - reqwest_wasi_test-b78f6a095419b422.wasm!__main_void
          39: 0x1c5a - reqwest_wasi_test-b78f6a095419b422.wasm!_start
       note: using the `WASMTIME_BACKTRACE_DETAILS=1` environment variable may show more debugging information
    2: wasm trap: wasm `unreachable` instruction executed

Thanks in advance for your response.

[seanmonstar]

Hey there! Supporting more environments is usually something we'd be happy to do. All of reqwest's WASM support is contributed by others, I don't have any active work in WASM. So, if you want to help propose how to add support, and implement it, that'd be welcome!

[k0pernicus]

Thanks Sean.
As I am getting into support for WASM (for servers, not browsers) I don't promise anything but I will look at the code later and check how I can modify this or this in order to get both browser & server (without wasm_bindgen) support.