Move pipe nonblocking setup to runtime

[peter-jerry-ye]

Why

Pipe async-end flags should be handled by the runtime side that creates the descriptors. Keeping the old MoonBit-side nonblocking path duplicates responsibility and keeps wasm pipe setup coupled to a platform check.

What

• Remove the wasm fd_util/set_nonblocking/unix import and MoonBit helper from fd_util.
• Stop calling the old setter from fd_util/pipe.
• Keep passing read/write async flags to the runtime pipe import.

Correctness

The runtime pipe import already receives both async-end flags before returning descriptors, so it can set descriptor mode at creation time. This leaves the wasm MoonBit code as a thin caller and avoids changing native async code.

Scope

This branch is based on main and only changes the wasm fd-util pipe path. The moonrun counterpart keeps the old wasm import ABI as a no-op for older guests until the compatibility shim is removed later.

[coveralls]

Coverage Report for CI Build 792

Coverage increased (+0.04%) to 77.202%

Details

• Coverage increased (+0.04%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

---

Coverage Stats

Relevant Lines:	4689
Covered Lines:	3620
Line Coverage:	77.2%
Coverage Strength:	12070.36 hits per line

---

💛 - Coveralls

[chatgpt-codex-connector]

💡 Codex Review

async/src/internal/event_loop/thread_pool.wasm.mbt

Line 587 in ba0821b

fn SpawnJob::result_handle(job : SpawnJob) -> @fd_util.Fd = "moonbitlang/async" "thread_pool/get_spawn_job_result_handle"

Pass the wasm spawn job handle to the result import

The thread_pool/get_spawn_job_result_handle import is given SpawnJob, but on wasm SpawnJob contains the Job valtype, while the runtime APIs in this file operate on the underlying JobHandle (for example OpenJob::fd_ffi(job.0.handle)). When @process.run or collect_* spawns a wasm process, the host import will not receive the job handle that was submitted, so the returned process handle can be invalid and waiting on the process can fail or hang. Make this import take JobHandle and call it with job.0.handle.

---

async/src/process/unix.mbt

Line 119 in ba0821b

Some(pipe) => pipe.fd()

Preserve blocking stdio for inherited async pipes

When stdout is an existing @pipe.PipeWrite from @pipe.pipe() (whose write end is created async/nonblocking), this now passes that fd directly to the Unix spawn path. The worker only applies posix_spawn_file_actions_adddup2, so the child inherits O_NONBLOCK; a program that writes enough output to fill the pipe can see EAGAIN instead of blocking. The temporary process pipes already have blocking child ends, but arbitrary ProcessOutput still needs child-side blocking without changing the parent's async handle.

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".