Re: [PATCH] rust/revocable: add try_with() convenience method

[Alexandre Courbot]

On Sun Mar 16, 2025 at 2:48 AM JST, Benno Lossin wrote:
> On Sat Mar 15, 2025 at 3:26 PM CET, Alexandre Courbot wrote:
>> On Sat Mar 15, 2025 at 11:17 PM JST, Danilo Krummrich wrote:
>>> On Sat, Mar 15, 2025 at 11:07:44PM +0900, Alexandre Courbot wrote:
>>>> I suppose drivers could add their own macros to do that automatically
>>>> and reduce code verbosity, at the cost of less cohesion across drivers.
>>>> Guess I'll go with that if I cannot come with anything better.
>>>
>>> Maybe we could do something more specific but yet generic on top (for the
>>> use-case above), but we still can't assume the exact error code a driver wants
>>> to derive from failing try_access(). So, maybe a driver specific wrapper is
>>> indeed what you want on top of what this patch provides.
>>
>> So be it! It's not that bad and more flexible in the end.
>
> You could have the following signature:
>
>     fn try_access_with<R>(&self, on_vacant: Error, f: impl FnOnce(&T) -> Result<R>) -> Result<R>;
>
> That will use the `on_vacant` error instead of hard coding ENXIO. But
> maybe it's better to just have such a wrapper in drivers that actually
> need it (ie even with the concrete error specified and not a parameter).
> You'll know better through actually trying to write a driver.

Yeah, having the extra on_vacant parameter would require callers to
specify the error they need every time, where it is supposed to be
a per-driver constant. So I guess a per-driver macro or wrapper would be
more ergonomic in the end.