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fix(node): await Promise returns from async JS hook handlers #61

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fix(node): await Promise returns from async JS hook handlers #61

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40 changes: 40 additions & 0 deletions bindings/node/__tests__/hooks.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -85,4 +85,44 @@ describe('JsHookRegistry', () => {
expect(parsed).toHaveProperty('custom', 'value')
expect(parsed).toHaveProperty('tool', 'grep')
})

it('supports async handlers returning Promise<string>', async () => {
const registry = new JsHookRegistry()
let handlerCalled = false
let receivedEvent = ''

registry.register('tool:pre', async (event: string, _data: string) => {
handlerCalled = true
receivedEvent = event
// Simulate async work (e.g. I/O)
await new Promise<void>(resolve => setImmediate(() => resolve()))

Copilot AI Apr 21, 2026

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This can be simplified to avoid an extra closure (e.g., pass resolve directly to setImmediate) while keeping the same behavior. It also makes the intent of ‘await one tick’ a bit clearer.

Suggested change
await new Promise<void>(resolve => setImmediate(() => resolve()))
await new Promise<void>(resolve => setImmediate(resolve))

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return JSON.stringify({ action: 'continue' })
}, 10, 'async-hook')

const result = await registry.emit('tool:pre', '{"tool":"grep"}')

expect(handlerCalled).toBe(true)
expect(receivedEvent).toBe('tool:pre')
expect(result.action).toBe(HookAction.Continue)
})

it('async handler returning deny short-circuits pipeline', async () => {
const registry = new JsHookRegistry()
let secondRan = false

registry.register('tool:pre', async (_event: string, _data: string) => {
await new Promise<void>(resolve => setImmediate(() => resolve()))
return JSON.stringify({ action: 'deny', reason: 'async blocked' })
}, 10, 'async-deny')
registry.register('tool:pre', (_event: string, _data: string) => {
secondRan = true
return JSON.stringify({ action: 'continue' })
}, 20, 'after')

const result = await registry.emit('tool:pre', '{"tool":"rm"}')

expect(result.action).toBe(HookAction.Deny)
expect(result.reason).toBe('async blocked')
expect(secondRan).toBe(false)
})
})
12 changes: 11 additions & 1 deletion bindings/node/src/hooks.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,14 +43,24 @@ impl HookHandler for JsHookHandlerBridge {
"{}".to_string()
});
Box::pin(async move {
let result_str: String =
// The JS handler may return either a bare string (synchronous) or a
// Promise<String> (async). `call_async` returns whatever the JS
// function returned — accept both via `Either`.
let ret: Either<String, napi::bindgen_prelude::Promise<String>> =
self.callback
.call_async((event, data_str))
.await
Comment on lines +46 to 52

Copilot AI Apr 21, 2026

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This change fixes the common async case, but any handler returning an unexpected type (e.g., an object) can still trigger a process-level fatal error if the underlying ThreadsafeFunction is configured with ErrorStrategy::Fatal (conversion into Either<...> would fail). Consider switching this bridge’s TSFN to a non-fatal strategy (e.g., CalleeHandled) and mapping conversion failures into HookError::HandlerFailed so user-land mistakes don’t hard-crash the host process.

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.map_err(|e| HookError::HandlerFailed {
message: e.to_string(),
handler_name: None,
})?;
let result_str: String = match ret {
Either::A(s) => s,
Either::B(promise) => promise.await.map_err(|e| HookError::HandlerFailed {
message: e.to_string(),
handler_name: None,
})?,
};
Comment on lines +57 to +63

Copilot AI Apr 21, 2026

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The HookError::HandlerFailed { message: e.to_string(), handler_name: None } mapping is duplicated (once for call_async(...).await and again for promise.await). To keep error handling consistent and reduce repetition, consider extracting this mapping into a small local closure/helper used in both places.

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let hook_result: HookResult = serde_json::from_str(&result_str).unwrap_or_else(|e| {
log::error!(
"SECURITY: Hook handler returned unparseable result — failing closed (Deny): {e} — json: {result_str}"
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