update examples and usage for wasm_bindgen

[jack-champagne]

Issue found when trying to implement an example similar to the one listed in the README. A change in the durable_object macro I believe now makes it so that including wasm_bindgen seems to be required. If not included, a confusing error occurs that is difficult to debug, likely from macro expansion. See error attached below.

error: the `self` argument is only allowed for functions in `impl` blocks.

       If the function is already in an `impl` block, did you perhaps forget to add `#[wasm_bindgen]` to the `impl` block?
 --> src/lib.rs:3:1
  |
3 | #[durable_object]
  | ^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in the attribute macro `durable_object` (in Nightly builds, run with -Z macro-backtrace for more info)

error: recursion limit reached while expanding `#[derive]`
 --> src/lib.rs:3:1
  |
3 | #[durable_object]
  | ^^^^^^^^^^^^^^^^^
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`durable-object-demo`)
  = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)

error: could not compile `durable-object-demo` (lib) due to 2 previous errors

[guybedford]

I believe I fixed this in #816, released in worker 0.6.4. Are you seeing this in that version or above or an earlier version?

[jack-champagne]

I was seeing this on 0.6.7 but I can check in 0.6.4 as well. For reference, here is my full src/lib.rs

on worker 0.6.7:

use worker::{durable_object, event, wasm_bindgen, Env, Request, Response, Result, State};

type User = String;
type Message = String;

#[durable_object]
pub struct Chatroom {
    users: Vec<User>,
    messages: Vec<Message>,
    state: State,
    env: Env, // access `Env` across requests, use inside `fetch`
}
impl DurableObject for Chatroom {
    fn new(state: State, env: Env) -> Self {
        Self {
            users: vec![],
            messages: vec![],
            state: state,
            env,
        }
    }
    async fn fetch(&self, _req: Request) -> Result<Response> {
        // do some work when a worker makes a request to this DO
        Response::ok(&format!("{} active users.", self.users.len()))
    }
}

#[event(fetch)]
async fn fetch(req: Request, env: Env, _ctx: worker::Context) -> Result<Response> {
    let ns = env.durable_object("CHATROOM")?;
    let stub = ns.id_from_name("chatroom-1")?.get_stub()?;
    stub.fetch_with_request(req).await
}

[jack-champagne]

Same error with same code but using worker v0.6.4:

worker 0.6.4 (same code) error:

error: the `self` argument is only allowed for functions in `impl` blocks.

       If the function is already in an `impl` block, did you perhaps forget to add `#[wasm_bindgen]` to the `impl` block?
 --> src/lib.rs:6:1
  |
6 | #[durable_object]
  | ^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in the attribute macro `durable_object` (in Nightly builds, run with -Z macro-backtrace for more info)

error: recursion limit reached while expanding `#[derive]`
 --> src/lib.rs:6:1
  |
6 | #[durable_object]
  | ^^^^^^^^^^^^^^^^^
  |
  = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`durable_object_demo`)
  = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)

error: could not compile `durable-object-demo` (lib) due to 2 previous errors

just a quick check to make sure I'm using the right version in my Cargo.lock

cargo tree | grep -e "worker"

gives:

├── worker v0.6.4
│   ├── worker-kv v0.9.0
│   ├── worker-macros v0.6.4 (proc-macro)
│   │   └── worker-sys v0.6.7
│   └── worker-sys v0.6.7 (*)
└── worker-macros v0.6.4 (proc-macro) (*)

[guybedford]

I just copied and pasted your exact code example into a test project with this Cargo.toml:

[package]
name = "rustworker"
version = "0.1.0"
edition = "2021"

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

[dependencies]
wasm-bindgen = "=0.2.105"
worker = { version = "0.6.7" }
worker-macros = { version = "0.6.7" }

and this wrangler.toml

name = "rustworker"
main = "build/worker/shim.mjs"
compatibility_date = "2025-11-01"

[build]
command = "cargo install -q worker-build && worker-build --release"

and it works fine for me via npx wrangler dev.

Let me know if that works for you, or please share replication instructions further.

[jack-champagne]

Thanks, just checked on v0.6.4 and v0.6.7 with the updated Project.toml -

Looks like it's working for both of those versions without use worker::wasm_bindgen anymore which is good. I think updating the generated project from cargo generate might be helpful for new users trying this stuff out - or alternatively finding a way for the macro to give a bit more info on whats gone wrong.

I've pushed a new commit to this pr that just updates the templates, not sure if this is the direction you'd want to take.

[jack-champagne]

Since I was able to reproduce locally, if my changes to the templates are not warranted this pull request can be closed.

[guybedford]

It looks like #816 isn't quite right if this is needed.

I think that macro fix needs to be changed to use worker::wasm_bindgen.

[jack-champagne]

I think you're right, I remember viewing this PR while I was trying to figure out what was wrong. I could not tell because I don't have a ton of experience with debugging rust macros/rust macros in general. I can give it a go

[guybedford]

Thanks for your feedback and thought on this - I've posted #869 which should fix this but please let me know if you see any further issues.

[jack-champagne]

Thanks, this change fixed the issue on the latest version. Closing this PR because of change in #869