Can't compile on WASM.

[cwahn]

My project fails to get compiled at some point.
Clearly, the issue was regarding the mio, which is not supported on web assembly.

so I have checked the dependency tree with cargo tree --target wasm32-unknown-unknown.

├── reqwest-websocket v0.4.4
│   ├── futures-util v0.3.31 (*)
│   ├── reqwest v0.12.9 (*)
│   ├── thiserror v2.0.9
│   │   └── thiserror-impl v2.0.9 (proc-macro)
│   │       ├── proc-macro2 v1.0.92 (*)
│   │       ├── quote v1.0.37 (*)
│   │       └── syn v2.0.90 (*)
│   ├── tokio v1.42.0
│   │   ├── bytes v1.9.0
│   │   ├── mio v1.0.2
│   │   ├── pin-project-lite v0.2.14
│   │   └── tokio-macros v2.4.0 (proc-macro)
│   │       ├── proc-macro2 v1.0.92 (*)
│   │       ├── quote v1.0.37 (*)
│   │       └── syn v2.0.90 (*)
│   ├── tracing v0.1.40 (*)
│   └── web-sys v0.3.76 (*)

It turns out that reqwest-websocket is the only library try to get mio involved in the dependency tree.
So I would like to know if any one compiles this without error for wasm32 target, is there any thing I should try.

[jgraef]

What is the exact error message when compiling? Or is there a way I could reproduce this?

reqwest-websocket for wasm32-unknown-unknown depends on tokio for the queues (mpsc and oneshot) and the tokio::select! macro. The dependency only enables features required for this.

When I run cargo tree I get no mio.

$ cargo tree --target wasm32-unknown-unknown

[...]
├── tokio v1.42.0
│   ├── pin-project-lite v0.2.15
│   └── tokio-macros v2.4.0 (proc-macro)
│       ├── proc-macro2 v1.0.92 (*)
│       ├── quote v1.0.37 (*)
│       └── syn v2.0.90 (*)
[...]

Do you have any other dependencies that might enable a feature with tokio that requires mio? Looks like the features net, process and signal pull in mio.

[cwahn]

Thank you for the swift reply.

Here is the error message.

   Compiling wasm-bindgen-backend v0.2.99
   Compiling futures-util v0.3.31
   Compiling futures-channel v0.3.31
   Compiling serde_json v1.0.128
   Compiling memchr v2.7.4
   Compiling bitflags v2.6.0
   Compiling mio v1.0.2
error[E0432]: unresolved import `crate::sys::IoSourceState`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/io_source.rs:14:5
   |
14 | use crate::sys::IoSourceState;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ no `IoSourceState` in `sys`

error[E0432]: unresolved import `crate::sys::tcp`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:17:17
   |
17 | use crate::sys::tcp::{bind, listen, new_for_addr};
   |                 ^^^ could not find `tcp` in `sys`

error[E0432]: unresolved import `crate::sys::tcp`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/stream.rs:15:17
   |
15 | use crate::sys::tcp::{connect, new_for_addr};
   |                 ^^^ could not find `tcp` in `sys`

error[E0433]: failed to resolve: could not find `Selector` in `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/poll.rs:321:18
    |
321 |             sys::Selector::new().map(|selector| Poll {
    |                  ^^^^^^^^ could not find `Selector` in `sys`

error[E0433]: failed to resolve: could not find `event` in `sys`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:24:14
   |
24 |         sys::event::token(&self.inner)
   |              ^^^^^ could not find `event` in `sys`

error[E0433]: failed to resolve: could not find `event` in `sys`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:38:14
   |
38 |         sys::event::is_readable(&self.inner)
   |              ^^^^^ could not find `event` in `sys`

error[E0433]: failed to resolve: could not find `event` in `sys`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:43:14
   |
43 |         sys::event::is_writable(&self.inner)
   |              ^^^^^ could not find `event` in `sys`

error[E0433]: failed to resolve: could not find `event` in `sys`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:68:14
   |
68 |         sys::event::is_error(&self.inner)
   |              ^^^^^ could not find `event` in `sys`

error[E0433]: failed to resolve: could not find `event` in `sys`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:99:14
   |
99 |         sys::event::is_read_closed(&self.inner)
   |              ^^^^^ could not find `event` in `sys`

error[E0433]: failed to resolve: could not find `event` in `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:129:14
    |
129 |         sys::event::is_write_closed(&self.inner)
    |              ^^^^^ could not find `event` in `sys`

error[E0433]: failed to resolve: could not find `event` in `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:151:14
    |
151 |         sys::event::is_priority(&self.inner)
    |              ^^^^^ could not find `event` in `sys`

error[E0433]: failed to resolve: could not find `event` in `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:173:14
    |
173 |         sys::event::is_aio(&self.inner)
    |              ^^^^^ could not find `event` in `sys`

error[E0433]: failed to resolve: could not find `event` in `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:183:14
    |
183 |         sys::event::is_lio(&self.inner)
    |              ^^^^^ could not find `event` in `sys`

error[E0433]: failed to resolve: could not find `event` in `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:221:26
    |
221 |                     sys::event::debug_details(f, self.0)
    |                          ^^^^^ could not find `event` in `sys`

error[E0433]: failed to resolve: could not find `tcp` in `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:105:18
    |
105 |             sys::tcp::accept(inner).map(|(stream, addr)| (TcpStream::from_std(stream), addr))
    |                  ^^^ could not find `tcp` in `sys`

error[E0433]: failed to resolve: could not find `udp` in `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/udp.rs:124:14
    |
124 |         sys::udp::bind(addr).map(UdpSocket::from_std)
    |              ^^^ could not find `udp` in `sys`

error[E0433]: failed to resolve: could not find `udp` in `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/udp.rs:546:14
    |
546 |         sys::udp::only_v6(&self.inner)
    |              ^^^ could not find `udp` in `sys`

error[E0412]: cannot find type `Selector` in module `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/poll.rs:272:20
    |
272 |     selector: sys::Selector,
    |                    ^^^^^^^^ not found in `sys`

error[E0412]: cannot find type `Selector` in module `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/poll.rs:728:44
    |
728 |     pub(crate) fn selector(&self) -> &sys::Selector {
    |                                            ^^^^^^^^ not found in `sys`

error[E0412]: cannot find type `Waker` in module `sys`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/waker.rs:79:17
   |
79 |     inner: sys::Waker,
   |                 ^^^^^ not found in `sys`
   |
help: consider importing one of these structs
   |
1  + use crate::Waker;
   |
1  + use std::task::Waker;
   |
help: if you import `Waker`, refer to it directly
   |
79 -     inner: sys::Waker,
79 +     inner: Waker,
   |

error[E0433]: failed to resolve: could not find `Waker` in `sys`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/waker.rs:87:14
   |
87 |         sys::Waker::new(registry.selector(), token).map(|inner| Waker { inner })
   |              ^^^^^ could not find `Waker` in `sys`
   |
help: consider importing one of these structs
   |
1  + use crate::Waker;
   |
1  + use std::task::Waker;
   |
help: if you import `Waker`, refer to it directly
   |
87 -         sys::Waker::new(registry.selector(), token).map(|inner| Waker { inner })
87 +         Waker::new(registry.selector(), token).map(|inner| Waker { inner })
   |

error[E0412]: cannot find type `Event` in module `sys`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:18:17
   |
18 |     inner: sys::Event,
   |                 ^^^^^ not found in `sys`
   |
help: consider importing this struct through its public re-export
   |
1  + use crate::event::Event;
   |
help: if you import `Event`, refer to it directly
   |
18 -     inner: sys::Event,
18 +     inner: Event,
   |

error[E0412]: cannot find type `Event` in module `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:187:55
    |
187 |     pub(crate) fn from_sys_event_ref(sys_event: &sys::Event) -> &Event {
    |                                                       ^^^^^ not found in `sys`
    |
help: consider importing this struct through its public re-export
    |
1   + use crate::event::Event;
    |
help: if you import `Event`, refer to it directly
    |
187 -     pub(crate) fn from_sys_event_ref(sys_event: &sys::Event) -> &Event {
187 +     pub(crate) fn from_sys_event_ref(sys_event: &Event) -> &Event {
    |

error[E0412]: cannot find type `Event` in module `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:191:41
    |
191 |             &*(sys_event as *const sys::Event as *const Event)
    |                                         ^^^^^ not found in `sys`
    |
help: consider importing this struct through its public re-export
    |
1   + use crate::event::Event;
    |
help: if you import `Event`, refer to it directly
    |
191 -             &*(sys_event as *const sys::Event as *const Event)
191 +             &*(sys_event as *const Event as *const Event)
    |

error[E0412]: cannot find type `Event` in module `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/event.rs:217:46
    |
217 |             struct EventDetails<'a>(&'a sys::Event);
    |                                              ^^^^^ not found in `sys`
    |
help: consider importing this struct through its public re-export
    |
1   + use crate::event::Event;
    |
help: if you import `Event`, refer to it directly
    |
217 -             struct EventDetails<'a>(&'a sys::Event);
217 +             struct EventDetails<'a>(&'a Event);
    |

error[E0412]: cannot find type `Events` in module `sys`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/events.rs:43:17
   |
43 |     inner: sys::Events,
   |                 ^^^^^^ not found in `sys`
   |
help: consider importing this struct through its public re-export
   |
1  + use crate::Events;
   |
help: if you import `Events`, refer to it directly
   |
43 -     inner: sys::Events,
43 +     inner: Events,
   |

error[E0433]: failed to resolve: could not find `Events` in `sys`
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/events.rs:94:25
   |
94 |             inner: sys::Events::with_capacity(capacity),
   |                         ^^^^^^ could not find `Events` in `sys`
   |
help: consider importing this struct through its public re-export
   |
1  + use crate::Events;
   |
help: if you import `Events`, refer to it directly
   |
94 -             inner: sys::Events::with_capacity(capacity),
94 +             inner: Events::with_capacity(capacity),
   |

error[E0412]: cannot find type `Events` in module `sys`
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/events.rs:189:47
    |
189 |     pub(crate) fn sys(&mut self) -> &mut sys::Events {
    |                                               ^^^^^^ not found in `sys`
    |
help: consider importing this struct through its public re-export
    |
1   + use crate::Events;
    |
help: if you import `Events`, refer to it directly
    |
189 -     pub(crate) fn sys(&mut self) -> &mut sys::Events {
189 +     pub(crate) fn sys(&mut self) -> &mut Events {
    |

error[E0425]: cannot find value `listener` in this scope
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:76:24
   |
76 |         set_reuseaddr(&listener.inner, true)?;
   |                        ^^^^^^^^ not found in this scope

error[E0425]: cannot find value `listener` in this scope
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:78:15
   |
78 |         bind(&listener.inner, addr)?;
   |               ^^^^^^^^ not found in this scope

error[E0425]: cannot find value `listener` in this scope
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:79:17
   |
79 |         listen(&listener.inner, 1024)?;
   |                 ^^^^^^^^ not found in this scope

error[E0425]: cannot find value `listener` in this scope
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:80:12
   |
80 |         Ok(listener)
   |            ^^^^^^^^ not found in this scope

error[E0425]: cannot find value `stream` in this scope
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/stream.rs:95:18
   |
95 |         connect(&stream.inner, addr)?;
   |                  ^^^^^^ not found in this scope

error[E0425]: cannot find value `stream` in this scope
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/stream.rs:96:12
   |
96 |         Ok(stream)
   |            ^^^^^^ not found in this scope

error[E0425]: cannot find function `set_reuseaddr` in this scope
  --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:76:9
   |
76 |         set_reuseaddr(&listener.inner, true)?;
   |         ^^^^^^^^^^^^^ not found in this scope

error[E0599]: no method named `register` found for struct `IoSource<std::net::TcpListener>` in the current scope
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:148:20
    |
148 |         self.inner.register(registry, token, interests)
    |                    ^^^^^^^^ method not found in `IoSource<TcpListener>`
    |
   ::: /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/io_source.rs:37:1
    |
37  | pub struct IoSource<T> {
    | ---------------------- method `register` not found for this struct
    |
    = help: items from traits can only be used if the trait is implemented and in scope
note: `Source` defines an item `register`, perhaps you need to implement it
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/source.rs:75:1
    |
75  | pub trait Source {
    | ^^^^^^^^^^^^^^^^

error[E0599]: no method named `reregister` found for struct `IoSource<std::net::TcpListener>` in the current scope
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:157:20
    |
157 |         self.inner.reregister(registry, token, interests)
    |                    ^^^^^^^^^^ method not found in `IoSource<TcpListener>`
    |
   ::: /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/io_source.rs:37:1
    |
37  | pub struct IoSource<T> {
    | ---------------------- method `reregister` not found for this struct
    |
    = help: items from traits can only be used if the trait is implemented and in scope
note: `Source` defines an item `reregister`, perhaps you need to implement it
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/source.rs:75:1
    |
75  | pub trait Source {
    | ^^^^^^^^^^^^^^^^

error[E0599]: no method named `deregister` found for struct `IoSource<std::net::TcpListener>` in the current scope
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:161:20
    |
161 |         self.inner.deregister(registry)
    |                    ^^^^^^^^^^ method not found in `IoSource<TcpListener>`
    |
   ::: /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/io_source.rs:37:1
    |
37  | pub struct IoSource<T> {
    | ---------------------- method `deregister` not found for this struct
    |
    = help: items from traits can only be used if the trait is implemented and in scope
note: `Source` defines an item `deregister`, perhaps you need to implement it
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/source.rs:75:1
    |
75  | pub trait Source {
    | ^^^^^^^^^^^^^^^^

   Compiling keyboard-types v0.7.0
error[E0308]: mismatched types
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/listener.rs:237:9
    |
237 | /         unsafe {
238 | |             #[cfg(any(unix, target_os = "hermit", target_os = "wasi"))]
239 | |             {
240 | |                 net::TcpListener::from_raw_fd(listener.into_raw_fd())
...   |
245 | |             }
246 | |         }
    | |_________^ expected `TcpListener`, found `()`

error[E0599]: no method named `register` found for struct `IoSource<std::net::TcpStream>` in the current scope
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/stream.rs:330:20
    |
330 |         self.inner.register(registry, token, interests)
    |                    ^^^^^^^^ method not found in `IoSource<TcpStream>`
    |
   ::: /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/io_source.rs:37:1
    |
37  | pub struct IoSource<T> {
    | ---------------------- method `register` not found for this struct
    |
    = help: items from traits can only be used if the trait is implemented and in scope
note: `Source` defines an item `register`, perhaps you need to implement it
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/source.rs:75:1
    |
75  | pub trait Source {
    | ^^^^^^^^^^^^^^^^

error[E0599]: no method named `reregister` found for struct `IoSource<std::net::TcpStream>` in the current scope
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/stream.rs:339:20
    |
339 |         self.inner.reregister(registry, token, interests)
    |                    ^^^^^^^^^^ method not found in `IoSource<TcpStream>`
    |
   ::: /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/io_source.rs:37:1
    |
37  | pub struct IoSource<T> {
    | ---------------------- method `reregister` not found for this struct
    |
    = help: items from traits can only be used if the trait is implemented and in scope
note: `Source` defines an item `reregister`, perhaps you need to implement it
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/source.rs:75:1
    |
75  | pub trait Source {
    | ^^^^^^^^^^^^^^^^

error[E0599]: no method named `deregister` found for struct `IoSource<std::net::TcpStream>` in the current scope
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/stream.rs:343:20
    |
343 |         self.inner.deregister(registry)
    |                    ^^^^^^^^^^ method not found in `IoSource<TcpStream>`
    |
   ::: /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/io_source.rs:37:1
    |
37  | pub struct IoSource<T> {
    | ---------------------- method `deregister` not found for this struct
    |
    = help: items from traits can only be used if the trait is implemented and in scope
note: `Source` defines an item `deregister`, perhaps you need to implement it
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/source.rs:75:1
    |
75  | pub trait Source {
    | ^^^^^^^^^^^^^^^^

error[E0308]: mismatched types
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/tcp/stream.rs:419:9
    |
419 | /         unsafe {
420 | |             #[cfg(any(unix, target_os = "hermit", target_os = "wasi"))]
421 | |             {
422 | |                 net::TcpStream::from_raw_fd(stream.into_raw_fd())
...   |
427 | |             }
428 | |         }
    | |_________^ expected `TcpStream`, found `()`

error[E0599]: no method named `register` found for struct `IoSource<std::net::UdpSocket>` in the current scope
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/udp.rs:624:20
    |
624 |         self.inner.register(registry, token, interests)
    |                    ^^^^^^^^ method not found in `IoSource<UdpSocket>`
    |
   ::: /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/io_source.rs:37:1
    |
37  | pub struct IoSource<T> {
    | ---------------------- method `register` not found for this struct
    |
    = help: items from traits can only be used if the trait is implemented and in scope
note: `Source` defines an item `register`, perhaps you need to implement it
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/source.rs:75:1
    |
75  | pub trait Source {
    | ^^^^^^^^^^^^^^^^

error[E0599]: no method named `reregister` found for struct `IoSource<std::net::UdpSocket>` in the current scope
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/udp.rs:633:20
    |
633 |         self.inner.reregister(registry, token, interests)
    |                    ^^^^^^^^^^ method not found in `IoSource<UdpSocket>`
    |
   ::: /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/io_source.rs:37:1
    |
37  | pub struct IoSource<T> {
    | ---------------------- method `reregister` not found for this struct
    |
    = help: items from traits can only be used if the trait is implemented and in scope
note: `Source` defines an item `reregister`, perhaps you need to implement it
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/source.rs:75:1
    |
75  | pub trait Source {
    | ^^^^^^^^^^^^^^^^

error[E0599]: no method named `deregister` found for struct `IoSource<std::net::UdpSocket>` in the current scope
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/udp.rs:637:20
    |
637 |         self.inner.deregister(registry)
    |                    ^^^^^^^^^^ method not found in `IoSource<UdpSocket>`
    |
   ::: /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/io_source.rs:37:1
    |
37  | pub struct IoSource<T> {
    | ---------------------- method `deregister` not found for this struct
    |
    = help: items from traits can only be used if the trait is implemented and in scope
note: `Source` defines an item `deregister`, perhaps you need to implement it
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/event/source.rs:75:1
    |
75  | pub trait Source {
    | ^^^^^^^^^^^^^^^^

error[E0308]: mismatched types
   --> /Users/chanwooahn/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-1.0.2/src/net/udp.rs:713:9
    |
713 | /         unsafe {
714 | |             #[cfg(any(unix, target_os = "hermit", target_os = "wasi"))]
715 | |             {
716 | |                 net::UdpSocket::from_raw_fd(socket.into_raw_fd())
...   |
721 | |             }
722 | |         }
    | |_________^ expected `UdpSocket`, found `()`

Some errors have detailed explanations: E0308, E0412, E0425, E0432, E0433, E0599.
For more information about an error, try `rustc --explain E0308`.
error: could not compile `mio` (lib) due to 47 previous errors
warning: build failed, waiting for other jobs to finish...

I haven't went through a couple more test.

It seems like it's not in single library introducing mio into the dependency graph.
Rather, it is combination of couple libraries

[dependencies]
...
dioxus = { version = "0.6.0", features = ["router"] }
reqwest = { version = "0.12", default-features = false }
reqwest-websocket = "0.4.4"
# ! Only macros and sync are supported in WASM
tokio = { version = "1.16.1", features = ["macros", "sync"] } 
...

Here are some of the relevant dependencies.
reqwest or reqwest-websocket alone does not introduce mio in to the dependency graph, but it seems having both does.
It is the same for tokio and request as well.

Can you reproduce this? or is this just on me?

[jgraef]

What does cargo tree --target wasm32-unknown-unknown -i -p mio say?

[cwahn]

mio v1.0.2
└── tokio v1.42.0
    └── reqwest-websocket v0.4.4
        └── merc-client v0.1.0 (/Users/chanwooahn/Documents/dev/rust/merc/merc-client)

Here it goes!

[jgraef]

Hmm, I really don't understand why it's pulling in mio. But I noticed that your crate doesn't appear in that dependency tree, even though it depends on tokio. You're using tokio 1.16. Have you tried using a newer version? This should not be an issue, but I'm honestly out of ideas.

[cwahn]

I understand.

This looks weird for me as well. I am trying to make a new crate and find the exact condition of issue.
Will let you know if I find any :)

[cwahn]

It seems like workspace does have effect between crates.
I have manage to build working crate on bare-bone project.
However, when I copy and paste all into the problematic workspace, it failed.

Nothing wrong with your crate.
I appreciate your rapid response though. :)

• A bit off topic, but unfortunately I change the web sockets crate to ws_stream_wasm because it support Stream with Sync. If there is any way to make your implementation support Sync it would be awesome.

[jgraef]

All dependencies are shared in a workspace, so if another crate in your workspace enables a mio-related feature for tokio that would affect your client crate as well. Although the dependencies are separate per target.

I started a PR a while ago that would make the wasm websocket Send + Sync, but I never got around finishing it. I appreciate the feedback.

Edit: I just worked a bit on that branch and it works fine for wasm now. WebSocket is now Send + Sync. But it doesn't work on native, since the underlying stream hyper::Upgraded is not Sync :(