> On Jul 26, 2024, at 6:42 PM, Christoph M. Becker <cmbecke...@gmx.de> wrote:
>
> I have only skimmed your suggestion, but it sounds quite similar to
> <https://wiki.php.net/rfc/skipparams>.
I would really love to hear from some of those who voted "no" ~9 years why they
did so, and if they still feel the same.
> On Jul 26, 2024, at 5:54 PM, Bilge <bi...@scriptfusion.com> wrote:
> When writing a function, we can specify defaults for its parameters, and when
> calling a function we can leverage those defaults implicitly by not
> specifying those arguments or by "jumping over" some of them using named
> parameters. However, we cannot explicitly use the defaults. But why would we
> want to?
>
> Sometimes we want to effectively inherit the defaults of a function we're
> essentially just proxying. One way to do that is copy and paste the entire
> method signature, but if the defaults of the proxied method change, we're now
> overriding them with our own, which is not what we wanted to do. It is
> possible, in a roundabout way, to avoid specifying the optional parameters by
> filtering them out (as shown in the next example). The final possibility is
> to use reflection and literally query the default value for each optional
> parameter, which is the most awkward and verbose way to inherit defaults.
>
> Let's use a concrete example for clarity.
>
> function query(string $sql, int $limit = PHP_INT_MAX, int $offset = 0);
>
> function myQuery(string $sql, ?int $limit = null, ?int $offset = null) {
> query(...array_filter(func_get_args(), fn ($arg) => $arg !== null));
> }
>
Yes, I run into that issue all the time. So much so that I adopted an
"optional args" pattern which itself has many downsides but in my code it has
had fewer downsides than doing it other ways.
So for your example I would write it like this (though I hate having to
double-quote the names of the optional args):
function query(string $sql, array $args = []);
function myQuery(string $sql, array $args = []) {
query($sql, $args);
}
myQuery("SELECT * FROM table;", ["offset" => 100]));
This is very flexible and a pattern that served me well for 10+ years.
But of course this has none of the type safety nor code-completion benefits of
named parameters, which I would sorely like to have.
> In this way we are able to filter out the null arguments to inherit the
> callee defaults, but this code is quite ugly. Moreover, it makes the
> (sometimes invalid) assumption that we're able to use `null` for all the
> optional arguments.
>
> In my new proposal for explicit callee defaults, it would be possible to use
> the `default` keyword to expressly use the default value of the callee in
> that argument position. For example, the above implementation for myQuery()
> could be simplified to the following.
>
> function myQuery(string $sql, ?int $limit = null, ?int $offset = null) {
> query($sql, $limit ?? default, $offset ?? default);
> }
>
> Furthermore, it would also be possible to "jump over" optional parameters
> without using named parameters.
>
To me, while nice I feel it is very much like only a quarter step in the right
direction.
I do not meaning to highjack your thread; feel free to ignore this if you feel
committed to pursing only your stated approach and are not interested in what I
would like to see. But I mention in hopes you and others see value in a more
complete approach:
To begin, we can already currently do this (although I do not see many people
doing it in PHP; fyi this approach is the norm for many Go programmers):
class QueryArgs {
public function __construct(
public ?int $limit = 100,
public ?int $offset = 0,
){}
}
function myQuery(string $sql, QueryArgs $args = new QueryArgs()) {
query($sql, $args);
}
myQuery("SELECT * FROM table;", new QueryArgs(offset:100));
I can only give my reasons for not doing it myself in PHP and speculate that
others may have similar reasons and/or have never even considered it:
1. Not having an easy and consistent way to declare the "args" class in the
same file where the functions that use it are declared which keeps it
out-of-sight and makes it harder to keep updated than it needs to be.
2. Having lots of visually annoying boilerplate that obscures a clear use-case.
What would be great IMO would be if PHP could elevate this concept to first
class and add syntax and features to streamline and empower its use. Imagine
if we could instead:
1. Define an "args" type which would be based on a class like enum is based on
a class:
args QueryArgs {
public ?int $limit = 100;
public ?int $offset = 0;
}
2. Declare a function to use those args, using your `default` keyword when they
are optional:
function myQuery(string $sql, QueryArgs $args = default) {
query($sql, $args);
}
3. And finally, allow a streamlined syntax to pass args:
myQuery("SELECT * FROM table;", {offset:100});
(I do not think we can or even should try to tackle the PSR-4 "every symbol in
its own file" problem here, so I am going to leave that for other potential
RFCs.)
-Mike
