Adds Rust bindgen/gloo-net based io implementation for JavaScript by Anunayj · Pull Request #1443 · payjoin/rust-payjoin

Anunayj · 2026-03-25T21:35:10Z

Pure Rust implementation of fetch_ohttp_keys using gloo-net and (too much) rust-wasmbindgen.

The Websocket Implementation is quite straightfoward as it uses gloo-net to access the WebSocket API. However, the fetch API does not support Proxy requests, so we bind to undici and (in a quite ugly fashion) make the HTTP(S) request thru the proxy.

It would likely have been more sensible to implement these as JS stubs, but I had quite a lot of fun ~~(actually I did not :P)~~ implementing these. Very overkill, probably pointless but ¯\_(ツ)_/¯

Actually I am unsure if this was a cleanest way to go about this (I still think pure JS stubs would have been easier), maybe this code should instead reside in payjoin-ffi, open to opinions.

AI Disclaimer

AI (Gemini mostly) was used extensively for consulting on how to approach, or implement certain things. However the key implementation was handwritten while consulting snippets of code. Test cases were written with help of AI.

Closes: #1250

Pull Request Checklist

Please confirm the following before requesting review:

I have disclosed my use of
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in the body of this PR.
I have read CONTRIBUTING.md and rebased my branch to produce hygienic commits.

Note for Reviewers: Would recommend reviewing commit by commit. I've broken the change down into small set of changes for ease of review.

I have been using RustRover for development, and it generates and saves configurations in .idea/

Also Allow IoError inner message to be read via a uniffi export

Adds pollyfills for WebSocket and File API (required by unidici). Node > 21 actually doesn't need these pollyfills, neither does the browser. I've not tested these changes in the browser yet.

Pure Rust implementation of fetch_ohttp_keys using gloo-net and (too much rust-wasmbindgen). The Websocket Implementation is quite straightfoward as it uses gloo-net to access the WebSocket API. However, the fetch API does not support Proxy requests, so we bind to uncidi and (in a quite ugly fashion) make the HTTP(S) request thru the proxy. Messy! It would likely have been more sensible to implement these as JS stubs, but I had quite a lot of fun implementing these. lockfiles were generated by using the script in contrib/ +----------------------+ | fetch_ohttp_keys() | +----------+-----------+ | v +----------+-----------+ | Detect JS Runtime | +----+------------+----+ | | (process) (Browser/Worker) | | v v +---------+ (fail) +-------------------+ | undici |--------->| WebSocket + | | Proxy | | rustls TLS Stream | +---------+ +-------------------+ | | | (success) | v v +----------------------------------------+ | OHTTP Relay | +----------------------------------------+ | v +----------------------------------------+ | Payjoin Directory | +----------------------------------------+ Closes: payjoin#1250

service.fetchOhttpKeysWithCert is still using NAAPI API. These test check basic functionality.

Copilot

Pull request overview

Adds a WASM/JavaScript-capable IO layer to fetch OHTTP keys (to address the lack of io in JS bindings), and wires it through the UniFFI JavaScript package with new integration tests and required dependencies.

Changes:

Introduces a wasm32 IO implementation that fetches OHTTP keys via undici (CONNECT proxy) and a WebSocket/TLS fallback.
Refactors IO error types so native/wasm share a single payjoin::io::Error/InternalError surface.
Exposes io via payjoin-ffi and updates the JS package (polyfills, deps, tests, CI helper script).

Reviewed changes

Copilot reviewed 12 out of 17 changed files in this pull request and generated 12 comments.

Show a summary per file

File	Description
payjoin/src/core/io/wasm.rs	New wasm32 IO backend using undici + WebSocket/TLS strategy.
payjoin/src/core/io/native.rs	Adapts native IO backend to shared error types in `io/mod.rs`.
payjoin/src/core/io/mod.rs	New shared `io` module defining public `Error`/`InternalError` and conversion macro.
payjoin/Cargo.toml	Adds wasm32 dependencies needed for the new wasm IO backend.
payjoin-ffi/src/lib.rs	Conditionally exports a new `io` module when the `io` feature is enabled.
payjoin-ffi/src/io.rs	New UniFFI-exported async wrappers for fetching OHTTP keys.
payjoin-ffi/javascript/ubrn.config.yaml	Enables `io` + `_manual-tls` features for the JS/WASM build.
payjoin-ffi/javascript/test/integration.test.ts	Adds JS integration tests exercising the WASM IO path.
payjoin-ffi/javascript/src/polyfills.ts	Adds Node polyfills for `File` and `WebSocket`.
payjoin-ffi/javascript/src/index.ts	Loads polyfills before exporting generated bindings.
payjoin-ffi/javascript/package.json	Adds `undici` and `ws` dependencies (and type deps).
payjoin-ffi/javascript/package-lock.json	Lockfile updates for the new JS dependencies.
payjoin-ffi/javascript/contrib/test.sh	New helper script to install deps, generate bindings, and run JS tests.
payjoin-ffi/Cargo.toml	Adds `io` feature that enables `payjoin/io`.
Cargo-recent.lock	Lock updates for new Rust deps (wasm IO + toolchain transitive changes).
Cargo-minimal.lock	Lock updates for new Rust deps (wasm IO + toolchain transitive changes).
.gitignore	Ignores `.idea` project files.

Files not reviewed (1)

payjoin-ffi/javascript/package-lock.json: Language not supported

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Copilot · 2026-03-25T21:41:56Z

payjoin-ffi/javascript/src/polyfills.ts

@@ -0,0 +1,23 @@
+import buffer from "node:buffer";


In an ESM build, import buffer from "node:buffer" will fail at runtime because node:buffer does not provide a default export. Use a namespace or named import (e.g., import * as buffer from "node:buffer" or import File directly) to avoid SyntaxError: ... does not provide an export named 'default'.

Suggested change

import buffer from "node:buffer";

import * as buffer from "node:buffer";

Copilot · 2026-03-25T21:41:57Z

payjoin-ffi/javascript/src/index.ts

+import "./polyfills.js";
+


polyfills.ts imports Node-only modules (node:buffer, ws) and index.ts now imports it unconditionally. That will break browser consumers (and contradicts the package.json browser field) because those modules can’t be resolved in browser bundlers. Consider a Node-specific entrypoint, conditional import, or an alternate index.web.ts that omits these polyfills.

Copilot · 2026-03-25T21:41:57Z

payjoin-ffi/javascript/package.json

+    "dependencies": {
+        "undici": "^7.24.3",
+        "ws": "^8.19.0"
    }


The selected undici version has an engines constraint of node >=20.18.1 (see package-lock), but the new polyfill comments imply support for Node 18/19. Either document/encode the new minimum Node version (e.g., via engines in package.json / CI config) or pin undici to a version that supports the intended Node range.

Copilot · 2026-03-25T21:41:57Z

payjoin-ffi/javascript/src/polyfills.ts

+// Reqired for Node.JS version < 20,
+// buffer.File is not available in all v18 and v19 versions as it was backported


Typo in comment: Reqired → Required. (Also consider using Node.js instead of Node.JS for consistency.)

Copilot · 2026-03-25T21:41:57Z

payjoin/src/core/io/wasm.rs

+    };
+
+    let ohttp_key_bytes = {
+        // call unidici fetch(), and jump through multiple hoops to get a Vec() out of the response


Typo in comment: unidici → undici.

Suggested change

// call unidici fetch(), and jump through multiple hoops to get a Vec() out of the response

// call undici fetch(), and jump through multiple hoops to get a Vec() out of the response

Copilot · 2026-03-25T21:41:58Z

payjoin/Cargo.toml

 [target.'cfg(target_arch = "wasm32")'.dependencies]
 web-time = "1.1.0"
+getrandom = { version = "0.4.2", features = ["wasm_js"] }
+js-sys = "0.3.85"
+gloo-net = { version = "0.6.0", features = ["io-util"] }
+gloo-utils = { version = "0.2.0", features = ["serde"] }
+ring = { version = "0.17.14", default-features = false, features = ["wasm32_unknown_unknown_js"] }
+futures = { version = "0.3.28"}
+futures-rustls = { version = "0.26.0", default-features = false, features = ["ring"] }
+webpki-roots = "1.0.5"
+rustls-pki-types = { version = "1.14.0", default-features = false, features = ["web"] }
+wasm-bindgen = "0.2"
+wasm-bindgen-futures = "0.4"
+serde-wasm-bindgen = "0.6"
+base64 = "0.21"


These wasm32-only dependencies are currently unconditional for any wasm32 build of payjoin, even when the io feature is disabled. This increases build time and binary size for WASM consumers that don’t need IO. Consider making them optional = true and enabling them only via the io feature (or a dedicated wasm-io feature), e.g. using feature-gated deps instead of always-on target deps.

Copilot · 2026-03-25T21:41:58Z

payjoin/src/core/io/wasm.rs

@@ -0,0 +1,360 @@
+//! WASM IO implementation.
+
+use std::fmt::{Debug, Formatter};


Debug is imported but not used (#[derive(Debug)] doesn’t require importing the trait). This will trigger an unused import warning in WASM builds; consider removing Debug from the import list.

Suggested change

use std::fmt::{Debug, Formatter};

use std::fmt::Formatter;

Copilot · 2026-03-25T21:41:58Z

payjoin/src/core/io/wasm.rs

+    // if we're not running in a browser
+    if !matches!(runtime, Runtime::BrowserMain | Runtime::WebWorker) {
+        if let Ok(keys) = fetch_via_http_connect(&relay, &directory, cert.as_deref()).await {
+            return Ok(keys);
+        }
+    }
+
+    fetch_via_websocket(relay, directory, cert.as_deref()).await


fetch_ohttp_keys_strategy discards the concrete error from fetch_via_http_connect and silently falls back to the WebSocket strategy. This can mask real failures (e.g., proxy misconfiguration, TLS failures) and make debugging difficult. Consider preserving the first error and returning a combined error if the fallback also fails (or only falling back for specific error kinds).

Copilot · 2026-03-25T21:41:58Z

payjoin/src/core/io/wasm.rs

+        let response = fetch(directory_url.as_str(), &fetch_options)
+            .map_err(InternalErrorInner::ProxyFetchFailed)?;
+        let response =
+            JsFuture::from(response).await.map_err(InternalErrorInner::ProxyFetchFailed)?;
+        let response: Response = response.unchecked_into();
+        Uint8Array::new(
+            &JsFuture::from(response.array_buffer())
+                .await
+                .map_err(|_e| InternalErrorInner::InvalidResponse)?,
+        )
+        .to_vec()
+    };
+
+    OhttpKeys::decode(&ohttp_key_bytes).map_err(Error::from)


fetch_via_http_connect decodes the response body without checking the HTTP status. This makes the WASM implementation inconsistent with the native one (which returns UnexpectedStatusCode) and may turn server errors into misleading decode errors. Bind the Response.status (and ideally ok) property and return Error::UnexpectedStatusCode on non-success statuses.

Copilot · 2026-03-25T21:41:59Z

payjoin/src/core/io/wasm.rs

+    let ohttp_keys_req =
+        format!("GET /ohttp-keys HTTP/1.1\r\nHost: {}\r\nConnection: close\r\n\r\n", host_header);


The WebSocket strategy sends GET /ohttp-keys but the rest of the codebase (and the RFC9540 gateway path used elsewhere) fetches keys from /.well-known/ohttp-gateway. This looks like the wrong endpoint for keys retrieval via the relay’s ws-bootstrap mechanism. Update the request line to use the gateway path so it matches the server behavior.

Suggested change

let ohttp_keys_req =

format!("GET /ohttp-keys HTTP/1.1\r\nHost: {}\r\nConnection: close\r\n\r\n", host_header);

let ohttp_keys_req = format!(

"GET /.well-known/ohttp-gateway HTTP/1.1\r\nHost: {}\r\nConnection: close\r\n\r\n",

host_header

);

Wait right yea, now I'm starting to question how was this working in my testing..

Anunayj added 6 commits March 26, 2026 01:11

Add .idea/ to gitignore

f5a587d

I have been using RustRover for development, and it generates and saves configurations in .idea/

Revert io module removal from payjoin-ffi

a8c7df8

Also Allow IoError inner message to be read via a uniffi export

Add polyfills for node < 21 support

c33e8ca

Adds pollyfills for WebSocket and File API (required by unidici). Node > 21 actually doesn't need these pollyfills, neither does the browser. I've not tested these changes in the browser yet.

Enable compilation of io module

4d956e2

Add integration tests testing fetchOhttpKeysWithCert

8cdca9f

service.fetchOhttpKeysWithCert is still using NAAPI API. These test check basic functionality.

Copilot AI review requested due to automatic review settings March 25, 2026 21:35

Copilot started reviewing on behalf of Anunayj March 25, 2026 21:35 View session

Copilot AI reviewed Mar 25, 2026

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Adds Rust bindgen/gloo-net based io implementation for JavaScript#1443

Adds Rust bindgen/gloo-net based io implementation for JavaScript#1443
Anunayj wants to merge 6 commits intopayjoin:masterfrom
Anunayj:io-javascript

Anunayj commented Mar 25, 2026 •

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Anunayj Mar 25, 2026 •

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	import buffer from "node:buffer";
	import * as buffer from "node:buffer";

		// Reqired for Node.JS version < 20,
		// buffer.File is not available in all v18 and v19 versions as it was backported

	// call unidici fetch(), and jump through multiple hoops to get a Vec() out of the response
	// call undici fetch(), and jump through multiple hoops to get a Vec() out of the response

		@@ -0,0 +1,360 @@
		//! WASM IO implementation.

		use std::fmt::{Debug, Formatter};

		let ohttp_keys_req =
		format!("GET /ohttp-keys HTTP/1.1\r\nHost: {}\r\nConnection: close\r\n\r\n", host_header);

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Anunayj commented Mar 25, 2026 •

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