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Subject: Re: [PHP-DEV] [VOTE] True Async RFC 1.6
In-Reply-To: <65869feb-d518-4de3-8c10-115e3ba7dce7@rwec.co.uk>
Date: Tue, 25 Nov 2025 08:11:27 +1300
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To: "Rowan Tommins [IMSoP]" <imsop.php@rwec.co.uk>
From: jbafford@zort.net (John Bafford)

Hi Rowan,

> On Nov 25, 2025, at 02:57, Rowan Tommins [IMSoP] =
<imsop.php@rwec.co.uk> wrote:
>=20
> On 24/11/2025 13:20, Edmond Dantes wrote:
>> This makes it impossible to accidentally shoot yourself in the foot. =
A
>> developer can still do something silly by explicitly passing objects
>> between coroutines, but now they are doing it consciously.
>=20
>=20
> Again, you completely avoided my question, and went back to ambiguous =
statements about "a developer".
>=20
> To stick to my personas:
>=20
> - SDK Susie does not know what implementation of LoggerInterface will =
be passed to her library. How does she know if it is safe to use in her =
asynchronous code?
>=20
> - Legacy Les is using a LoggerInterface implementation written years =
ago. How does he know whether it is acceptable for use with Susie's =
library?


I would argue that LoggerInterface only accounts for a synchronous =
implementation. It is impossible for an asynchronous implementation to =
meet the requirements of the interface.

An AsyncLoggerInterface would be required. However, any synchronous =
implementation that otherwise matches the requirements would implicitly =
match. (Any non-asynchronous function is effectively the same as an =
asynchronous function that has no suspension points.)

Effectively, we would need something like:

```
interface LoggerInterface extends AsyncLoggerInterface {
	public function log($level, $message, array $context =3D []);
	...
}

interface AsyncLogerInterface {
	public function log($level, $message, array $context =3D []) =
async;
	...
}
```

So if SDK Susie can certify that _their_ library will work correctly =
with an async logger, then they can indicate that by accepting an =
AsyncLoggerInterface (in place of, or separately from, a =
LoggerInterface). This is just an assertion that SDK Susie's library =
will work correctly in the face of an async logger. It's up to Async =
Alice and Beginner Bob to make sure they don't somehow footgun =
themselves with their own (new) async code. Legacy Les isn't passing in =
anything async, so as long as Susie's SDK doesn't violate its prior =
synchronous contract, Les shouldn't have anything to worry about.

-John