node:child_process: honor spawn and exec option semantics beyond cwd/env/shell

[andrewtdiz]

Summary

Perry's node:child_process implementation now has real spawn, fork, exec, execFile, and sync helpers, but the option handling is still limited to cwd, env, and shell. Current Node exposes a much wider option contract across these APIs, including stdio, input, timeout, maxBuffer, killSignal, signal, argv0, detached, uid, gid, and platform flags.

That means code using standard Node child-process controls can compile against Perry's surface but run with materially different behavior: stdio is always piped for live spawn/fork, timeouts and AbortSignals are ignored, sync input is not fed to stdin, maxBuffer limits are not enforced, uid/gid are not applied, and kill-signal/argv0/detached semantics are absent.

Evidence

• Current Node docs list the broader option surface across child_process.exec, execFile, fork, spawn, execSync, execFileSync, and spawnSync, including uid/gid, stdio, input, signal, timeout, killSignal, maxBuffer, argv0, and related platform flags: https://nodejs.org/api/child_process.html
• crates/perry-runtime/src/child_process/mod.rs:1118-1122 states the current helpers apply only common host-portable options and explicitly says anything not listed, including stdio, timeout, and maxBuffer, is still ignored.
• crates/perry-runtime/src/child_process/mod.rs:1137-1172 implements cp_apply_options() with only cwd and env handling.
• crates/perry-runtime/src/child_process/mod.rs:1186-1220 adds shell handling around cp_build_command() and then delegates back to the limited cp_apply_options() path.
• crates/perry-runtime/src/child_process/reactor.rs:357-409 always creates stdin/stdout/stderr pipe objects and configures the live child with Stdio::piped() regardless of a user stdio option.
• crates/perry-runtime/src/child_process/fork.rs:56-119 similarly always constructs stdio pipe objects plus fd 3 IPC and applies only the same limited options before forcing all standard streams to Stdio::piped().
• test-files/test_parity_child_process.ts:100-128 currently probes only basic ChildProcess shapes and does not exercise these option semantics.

Duplicate check

Searched issues and PRs for:

• child_process stdio timeout maxBuffer input killSignal AbortSignal uid gid argv0 detached windowsHide
• child_process options stdio timeout maxBuffer
• subprocess Symbol.dispose child_process

I found no open or closed tracker for this remaining option-semantics gap. This is separate from the closed streaming/IPC work around spawn/fork (#1933/#1934) and from the existing process-side IPC issue (#2529).

Acceptance sketch

• spawn / fork respect Node stdio forms and expose subprocess.stdin/stdout/stderr/stdio nullability accordingly.
• spawn / fork honor argv0, detached, uid, gid, signal, timeout, and killSignal where supported by the host platform.
• exec / execFile / sync variants honor timeout, maxBuffer, killSignal, signal, uid, gid, and input/stdio behavior where applicable.
• Unsupported platform cases should fail with Node-shaped errors or documented Node-compatible no-op behavior rather than silently ignoring options.
• Add parity tests that cover deterministic cases: stdio: 'ignore'/array nullability, spawnSync({ input }), small maxBuffer, timeout/AbortSignal termination, and option validation.

Note: this issue was confirmed from committed source and current Node docs; no local target/release/perry binary was available in this checkout for a fresh runtime probe.

[andrewtdiz]

I’m taking a narrow deterministic subset of this with #3079 as a focused node:child_process setup parity cut.\n\nIntended PR scope: option handling that sits on the same setup/exec path and is deterministic in local parity tests, especially sync input, timeout, and maxBuffer behavior. Non-goals for this PR: full live spawn/fork stdio forms, AbortSignal/killSignal lifecycle semantics, uid/gid/detached/platform-specific flags, and child-side IPC.

[andrewtdiz]

Opened draft PR #4180 for the deterministic sync buffered subset of this issue: #4180

This PR covers input, maxBuffer, and timeout behavior for spawnSync, execSync, and execFileSync, plus the related setup-validation parity fixture.

[andrewtdiz]

I am taking another narrow deterministic slice of #2555.

Planned scope: live spawn() / fork() stdio ignore handling only:

• stdio: "ignore" makes stdin, stdout, stderr, and stdio[0..2] null and routes the OS descriptors to Stdio::null();
• array forms like ["pipe", "ignore", "ignore"] preserve the piped stream for fd 0 while making ignored fds null;
• fork(..., { stdio: ["ignore", "ignore", "ignore", "ipc"] }) keeps channel / IPC behavior while fd 0..3 entries match Node nullability.

Non-goals: inherit, numeric fd sharing, custom stream handles, async exec/execFile timeout/maxBuffer, AbortSignal/killSignal, uid/gid/detached/platform flags, and broad option validation.

[andrewtdiz]

Opened draft PR #4213 for a narrow live-stdio slice of this tracker: #4213

Scope covered:

• spawn(..., { stdio: "ignore" }) exposes stdin/stdout/stderr and stdio[0..2] as null, with fd 0..2 wired to OS null handles.
• Array forms like ["pipe", "ignore", "ignore"] preserve a piped stdin while ignored stdout/stderr are null.
• fork(..., { stdio: ["ignore", "ignore", "ignore", "ipc"] }) keeps fd 3 IPC/channel behavior while fd 0..2 are ignored/null.

Verification on the rebased branch:

• cargo fmt --all
• cargo check -p perry-runtime
• cargo build -p perry --release --quiet
• child_process parity --filter stdio-ignore: 1 pass / 0 fail
• child_process parity --filter fork-send-callback-closed: 1 pass / 0 fail

Note: current origin/main had a compile break from the missing process module_noop_function; I opened #4211 as a separate hotfix and included that commit locally in #4213 so current-base verification can run. #4213 can drop that commit after #4211 lands.

Remaining #2555 scope includes inherit/numeric/custom stream stdio forms, async exec/execFile timeout/maxBuffer semantics, AbortSignal/killSignal, uid/gid/detached/platform flags, and broader option validation.

[andrewtdiz]

Taking another focused deterministic slice of this tracker. Planned scope: live spawn/fork stdio inherit handling only: stdio: "inherit" and array entries using "inherit" should expose the corresponding stdin/stdout/stderr and stdio[] entries as null, while routing the host descriptors through inherited stdio; fork should preserve its required IPC channel behavior when fd 3 is "ipc". Non-goals: numeric fd sharing, custom stream handles, async exec/execFile timeout/maxBuffer, AbortSignal/killSignal, uid/gid/detached/platform flags, and broad option validation.