node -p resolves promises earlier in Node.js 22 than previous releases

[andreas-schwab]

EDIT: background from pscript test suite

On riscv64 the testsuite of the pscript python modules fails:

=================================== FAILURES ===================================
______________________ TestFunctions.test_async_and_await ______________________

self = <test_parser2.TestFunctions object at 0x7f2d4a4f2e10>

def test_async_and_await(self):
    if sys.version_info < (3, 6):
        return

    foo = py2js('async def foo(): return 42\n\n')
    spam = py2js('async def spam(): print(await foo())\n\n')
    eggs = py2js('async def eggs(): return await foo()\n\n')
    js = foo + spam + eggs

    assert 'Promise' in evaljs(js + 'foo()')
    assert 'Promise' in evaljs(js + 'spam()')
    assert 'Promise' in evaljs(js + 'eggs()')

    assert '42' in evaljs(js + 'spam()')

  assert '42' not in evaljs(js + 'eggs()')

E AssertionError: assert '42' not in 'Promise { 42 }'
E
E '42' is contained here:
E Promise { 42 }
E ? ++

pscript/tests/test_parser2.py:874: AssertionError
=========================== short test summary info ============================
FAILED pscript/tests/test_parser2.py::TestFunctions::test_async_and_await - A...
============= 1 failed, 223 passed, 2 skipped in 670.27s (0:11:10) =============

This is a regression from node21:

$ node22 -p -e 'var foo; foo = async function flx_foo () { return 42; }; var eggs; eggs = async function flx_eggs () { return await foo(); }; eggs()'
Promise { 42 }
$ node21 -p -e 'var foo; foo = async function flx_foo () { return 42; }; var eggs; eggs = async function flx_eggs () { return await foo(); }; eggs()'
Promise { <pending> }

[joyeecheung]

It looks like what you are really reporting is something more like

$ node20 -p 'var foo; foo = async function flx_foo () { return 42; }; var eggs; eggs = async function flx_eggs () { return await foo(); }; eggs()'
Promise { <pending> }

$ node21 -p 'var foo; foo = async function flx_foo () { return 42; }; var eggs; eggs = async function flx_eggs () { return await foo(); }; eggs()'
Promise { 42 }

I can reproduce it on macOS + arm64 so I don't think it's a riscv64 issue.

I am not sure if this counts as a regression, however, there is no clear rule about when/whether the promises should be resolved before node -p prints something - or generally node -p has a lot of undocumented areas and undefined behaviors. It looks more like undefined behaviors that you should not rely on?

[aduh95]

It's not a bug, it's a feature: #52172

[joyeecheung]

Closing since this is a semver-major feature.