fix(test): randomBytes async callback test asserted pre-#6430 inline timing

[TheHypnoo]

What

crypto::random::tests::native_dispatch_random_bytes_value_form_fires_callback fails on main (verified at 8b2c736ed, macOS arm64):

panicked at crates/perry-stdlib/src/crypto/random.rs:906:9:
randomBytes callback must fire

The other 96 tests in perry-stdlib pass. A permanently red test in the per-crate CI scope teaches everyone to ignore that crate's results, so this closes it.

Why it fails

The test's assumption broke — the dispatch path is fine.

#6430 moved the async randomBytes callback onto a macrotask:

-    call_node_style_callback2(callback_bits, null, value);   // inline
+    perry_runtime::timer::js_set_immediate_callback_args(cb_ptr, args.as_ptr(), 2);

That is correct and deliberate. Node runs randomBytes on the libuv threadpool, so the (err, buffer) callback fires a loop iteration later, never inline. The test predates #6430, asserted synchronous firing, and was never updated.

The value-form dispatch itself still works: the "randomBytes" if args_len >= 2 arm routes to js_crypto_random_bytes_async, the callback lands with err = null and a Buffer pointer — just one macrotask later.

Change

Test only. Assert the callback does not fire inline, drain the callback-timer queue, then check the delivered arguments:

assert!(!CB_FIRED.with(|f| f.get()), "randomBytes callback must not fire synchronously");
perry_runtime::timer::js_callback_timer_tick();
assert!(CB_FIRED.with(|f| f.get()), "randomBytes callback must fire");

This locks in #6430's macrotask timing rather than the behavior it replaced.

Validation

cargo test --lib -p perry-stdlib
test result: ok. 97 passed; 0 failed; 0 ignored

./scripts/check_file_size.sh OK. cargo fmt --all leaves this diff unchanged (it does reformat crates/perry-hir/src/lower/builder_fold.rs, pre-existing drift on main, left alone here).

One thing worth knowing

CALLBACK_TIMERS is a process-global mutex, but agent::CURRENT_AGENT is thread-local and defaults to PRIMARY_AGENT, so every cargo test thread passes agent::owns(). A test that calls js_callback_timer_tick() can therefore drain and run another test thread's immediates. That is safe today only because nothing else in the perry-stdlib lib-test binary schedules callback timers (webcrypto/digest.rs schedules immediates but has no tests). Worth checking before a second timer-using test lands in this crate.

No version bump, no CHANGELOG.md edit; changelog fragment added under changelog.d/.

Summary by CodeRabbit

• Tests

  • Updated asynchronous crypto.randomBytes coverage to verify callbacks execute on a later task rather than synchronously.
  • Added checks confirming callback timing and expected (error, buffer) results.

• Documentation

  • Updated the changelog to reflect the test-only correction; runtime behavior is unchanged.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 505c980a-14eb-4e6b-bab8-b9050e250a63

📥 Commits

Reviewing files that changed from the base of the PR and between 8b2c736 and b17e095.

📒 Files selected for processing (2)

• changelog.d/6838-random-bytes-async-test-macrotask.md
• crates/perry-stdlib/src/crypto/random.rs

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📝 Walkthrough

Walkthrough

The random bytes native dispatch test now verifies callback execution on a macrotask, advances the callback timer queue, and validates the callback arguments. The changelog documents the test-only correction and confirms no runtime behavior changed.

Changes

Random bytes callback timing

Layer / File(s)	Summary
Asynchronous callback assertions crates/perry-stdlib/src/crypto/random.rs, changelog.d/6838-random-bytes-async-test-macrotask.md	The test asserts non-inline callback execution, processes the callback timer queue, validates (err, buffer), and documents the test-only change.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Suggested reviewers: proggeramlug

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately describes the test-only randomBytes async callback timing fix.
Description check	✅ Passed	The description covers the summary, root cause, change, and validation, with only minor omissions versus the template.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/random-bytes-async-test-macrotask

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