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fix(core): resolve a child's exit from /proc when Bun never reports it #40

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Merged
PierrotAWB merged 1 commit into from
Sep 3, 2026
Merged

fix(core): resolve a child's exit from /proc when Bun never reports it #40

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100 changes: 62 additions & 38 deletions packages/core/src/cross-spawn-spawner.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,8 @@ import {
ProcessId,
} from "effect/unstable/process/ChildProcessSpawner"
import * as NodeChildProcess from "node:child_process"
import { readFileSync } from "node:fs"
import * as os from "node:os"
import { PassThrough } from "node:stream"
import launch from "cross-spawn"
import { makeGlobalNode } from "./effect/app-node"
Expand Down Expand Up @@ -94,7 +96,31 @@ const toPlatformError = (
})
}

type ExitSignal = Deferred.Deferred<readonly [code: number | null, signal: NodeJS.Signals | null]>
type Exited = readonly [code: number | null, signal: NodeJS.Signals | null]
type ExitSignal = Deferred.Deferred<Exited>

// A zombie's /proc/<pid>/stat carries its waitpid status in field 52.
export const getExit = (stat: string): Exited | undefined => {
const fields = stat.slice(stat.lastIndexOf(")") + 2).split(" ")
if (fields[0] !== "Z" || fields.length < 50) return undefined
const status = Number(fields[49])
const sig = status & 0x7f
if (sig === 0) return [status >> 8, null]
const name = Object.keys(os.constants.signals)
.filter(isSignal)
.find((key) => os.constants.signals[key] === sig)
return [null, name ?? null]
}

const isSignal = (key: string): key is NodeJS.Signals => key in os.constants.signals

const getStat = (pid: number | undefined) => {
try {
return readFileSync(`/proc/${pid}/stat`, "utf8")
} catch {
return ""
}
}

export const make = Effect.gen(function* () {
const fs = yield* FileSystem.FileSystem
Expand Down Expand Up @@ -266,21 +292,23 @@ export const make = Effect.gen(function* () {

const spawn = (command: ChildProcess.StandardCommand, opts: NodeChildProcess.SpawnOptions) =>
Effect.callback<readonly [NodeChildProcess.ChildProcess, ExitSignal], PlatformError.PlatformError>((resume) => {
const signal = Deferred.makeUnsafe<readonly [code: number | null, signal: NodeJS.Signals | null]>()
const signal = Deferred.makeUnsafe<Exited>()
const proc = launch(command.command, command.args, opts)
let end = false
let exit: readonly [code: number | null, signal: NodeJS.Signals | null] | undefined
let exit: Exited | undefined
const finish = (found: Exited | undefined) => {
if (found && Deferred.doneUnsafe(signal, Exit.succeed(found))) clearInterval(watch)
}
// Bun can lose a child's exit and leave a zombie; /proc then reports it.
const watch =
process.platform === "linux" ? setInterval(() => finish(getExit(getStat(proc.pid))), 1_000).unref() : undefined
proc.on("error", (err) => {
clearInterval(watch)
resume(Effect.fail(toPlatformError("spawn", err, command)))
})
proc.on("exit", (...args) => {
exit = args
})
proc.on("close", (...args) => {
if (end) return
end = true
Deferred.doneUnsafe(signal, Exit.succeed(exit ?? args))
})
proc.on("close", (...args) => finish(exit ?? args))
proc.on("spawn", () => {
resume(Effect.succeed([proc, signal]))
})
Expand Down Expand Up @@ -342,6 +370,24 @@ export const make = Effect.gen(function* () {
})
}

const terminate = (
command: ChildProcess.StandardCommand,
proc: NodeChildProcess.ChildProcess,
signal: ExitSignal,
opts: ChildProcess.KillOptions | undefined,
) => {
const send = (s: NodeJS.Signals) => Effect.catch(killGroup(command, proc, s), () => killOne(command, proc, s))
const attempt = send(opts?.killSignal ?? "SIGTERM").pipe(Effect.andThen(Deferred.await(signal)), Effect.asVoid)
const bound = opts?.forceKillAfter
if (Predicate.isUndefined(bound)) return attempt

@cubic-dev-ai cubic-dev-ai Bot Sep 3, 2026

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P1: When a scoped command omits forceKillAfter and ignores SIGTERM, this branch waits for signal forever during scope finalization. Keep finalizer cleanup non-blocking without a bound, or give that path its own timeout.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At packages/core/src/cross-spawn-spawner.ts, line 382:

<comment>When a scoped command omits `forceKillAfter` and ignores SIGTERM, this branch waits for `signal` forever during scope finalization. Keep finalizer cleanup non-blocking without a bound, or give that path its own timeout.</comment>

<file context>
@@ -342,6 +370,24 @@ export const make = Effect.gen(function* () {
+    const send = (s: NodeJS.Signals) => Effect.catch(killGroup(command, proc, s), () => killOne(command, proc, s))
+    const attempt = send(opts?.killSignal ?? "SIGTERM").pipe(Effect.andThen(Deferred.await(signal)), Effect.asVoid)
+    const bound = opts?.forceKillAfter
+    if (Predicate.isUndefined(bound)) return attempt
+    // A child whose exit is never reported must not pin this fiber after SIGKILL.
+    return Effect.timeoutOrElse(attempt, {
</file context>

// An unreported exit must not pin the fiber after SIGKILL.
return Effect.timeoutOrElse(attempt, {
duration: bound,
orElse: () =>
send("SIGKILL").pipe(Effect.andThen(Deferred.await(signal)), Effect.timeoutOption(bound), Effect.asVoid),
})
}

const source = (handle: ChildProcessHandle, from: ChildProcess.PipeFromOption | undefined) => {
const opt = from ?? "stdout"
switch (opt) {
Expand Down Expand Up @@ -380,25 +426,13 @@ export const make = Effect.gen(function* () {
windowsHide: process.platform === "win32",
}),
Effect.fnUntraced(function* ([proc, signal]) {
const done = yield* Deferred.isDone(signal)
const kill = timeout(proc, command, command.options)
if (done) {
const [code] = yield* Deferred.await(signal)
if (process.platform === "win32") return yield* Effect.void
if (code !== 0 && Predicate.isNotNull(code)) return yield* Effect.ignore(kill(killGroup))
return yield* Effect.void
if (!(yield* Deferred.isDone(signal))) {
yield* Effect.ignore(terminate(command, proc, signal, command.options))
return
}
const send = (s: NodeJS.Signals) =>
Effect.catch(killGroup(command, proc, s), () => killOne(command, proc, s))
const sig = command.options.killSignal ?? "SIGTERM"
const attempt = send(sig).pipe(Effect.andThen(Deferred.await(signal)), Effect.asVoid)
const escalated = command.options.forceKillAfter
? Effect.timeoutOrElse(attempt, {
duration: command.options.forceKillAfter,
orElse: () => send("SIGKILL").pipe(Effect.andThen(Deferred.await(signal)), Effect.asVoid),
})
: attempt
return yield* Effect.ignore(escalated)
const [code] = yield* Deferred.await(signal)
if (process.platform === "win32" || code === 0 || Predicate.isNull(code)) return
yield* Effect.ignore(timeout(proc, command, command.options)(killGroup))
}),
)

Expand All @@ -424,17 +458,7 @@ export const make = Effect.gen(function* () {
),
)
}),
kill: (opts?: ChildProcess.KillOptions) => {
const sig = opts?.killSignal ?? "SIGTERM"
const send = (s: NodeJS.Signals) =>
Effect.catch(killGroup(command, proc, s), () => killOne(command, proc, s))
const attempt = send(sig).pipe(Effect.andThen(Deferred.await(signal)), Effect.asVoid)
if (!opts?.forceKillAfter) return attempt
return Effect.timeoutOrElse(attempt, {
duration: opts.forceKillAfter,
orElse: () => send("SIGKILL").pipe(Effect.andThen(Deferred.await(signal)), Effect.asVoid),
})
},
kill: (opts?: ChildProcess.KillOptions) => terminate(command, proc, signal, opts),
unref: Effect.sync(() => {
if (ref) {
proc.unref()
Expand Down
15 changes: 14 additions & 1 deletion packages/core/test/effect/cross-spawn-spawner.test.ts
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
import { describe, expect } from "bun:test"
import { describe, expect, test } from "bun:test"
import fs from "node:fs/promises"
import os from "node:os"
import path from "node:path"
Expand Down Expand Up @@ -60,6 +60,19 @@ async function gone(pid: number, timeout = 5_000) {
}

describe("cross-spawn spawner", () => {
describe("getExit", () => {
// /proc/<pid>/stat: pid, "(comm)", state, 48 fields, exit_code, ...
const stat = (state: string, status: number) =>
["2952", "(sh -c (x))", state, ...Array(48).fill("0"), String(status), "0", "0"].join(" ")

test("decodes a zombie's waitpid status", () => {
expect(CrossSpawnSpawner.getExit(stat("Z", 3 << 8))).toEqual([3, null])
expect(CrossSpawnSpawner.getExit(stat("Z", 9))).toEqual([null, "SIGKILL"])
expect(CrossSpawnSpawner.getExit(stat("S", 0))).toBeUndefined()
expect(CrossSpawnSpawner.getExit("")).toBeUndefined()
})
})

describe("basic spawning", () => {
fx.effect(
"captures stdout",
Expand Down
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