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Date: Wed, 12 Jul 2017 13:34:06 +0000
Message-ID: <CAOe2Xe7JpeHNWYDB-BBRDNhmNA7r3czc567JuFprcZ0ZhCvvBw@mail.gmail.com>
To: Aidan Woods <aidantwoods@gmail.com>
Cc: Rowan Collins <rowan.collins@gmail.com>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] array coalesce operator concept
From: mark@shust.com (Mark Shust)

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Hi Aidan,

I think you are correct on all points. The initial emit is just a warning,
so I think a suppressor will work just fine, since it does just pass over
the foreach if a traversable isn't passed in.

I could see this being helpful as it makes wrapping an if block around a
foreach not needed anymore (and in turn indenting the foreach another
level), replacing it with just a single character. I also think for those
that use linting tools and flag error suppressions, that an @as definition
could be easily ignored from such a linter. I develop with warnings on, and
see error suppressions as a sort of code smell, however I think the @as
definition could be really useful.

Cheers,
Mark

On Wed, Jul 12, 2017 at 4:22 AM Aidan Woods <aidantwoods@gmail.com> wrote:

> In theory you'd only *need* it be considered a suppressor? PHP already
> exhibits the skipping behaviour (it only emits a warning for the wrong type
> used in `foreach`, skips the loop, and then continues with remaining code).
>
> No harm in/there is probably value in, making that skipping intent
> explicit in a RFC though, but in terms of a patch, the warning would only
> need be suppressed as far as I can tell?
>
> Another thing I meant to mention -- this should not only be useful for
> arrays, but for any `Traversable` too (i.e. it should suppress errors
> generated in using a type not compatible with being iterated over in a
> `foreach` loop, and not just if the type is not array).
>
> Kind regards,
> Aidan
>
> On 12 July 2017 at 02:50, Mark Shust <mark@shust.com> wrote:
>
>> Aidan,
>>
>> Fantastic suggestion (@as) -- that is really the succinctness I was
>> initially looking for, and I think the intention makes a lot of sense. My
>> only concern/issue would be to make sure that isn't considered a
>> 'suppressor' -- but it's actual intent is to skip the execution of the
>> foreach to prevent the error/loop from occurring (rather than just
>> suppressing an error).
>>
>> Cheers,
>> Mark
>>
>>
>> On Tue, Jul 11, 2017 at 4:05 PM Aidan Woods <aidantwoods@gmail.com>
>> wrote:
>>
>>> If you were willing to accept
>>>
>>> ```
>>> foreach ($foo as $bar) if (is_array) {
>>> ...
>>> }
>>> ```
>>>
>>> as a solution, then you might as well use
>>>
>>> ```
>>> if (is_array($foo)) foreach ($foo as $bar) {
>>> ...
>>> }
>>> ```
>>>
>>> I wonder if this could be better achieved by expanding what the error
>>> suppression operator `@` can do? This entire behaviour seems more like an
>>> error suppression action on `foreach` to me, otherwise should we consider
>>> coalescing operators for other types/creating a more generic one?
>>>
>>> Going back to the error suppression operator:
>>>
>>> e.g. perhaps
>>>
>>> ```
>>> foreach ($foo @as $bar) {
>>> ...
>>> }
>>> ```
>>>
>>> could prevent skip past execution of the entire foreach block if there
>>> is an error using $foo as an array. So might make most sense to place the
>>> `@` on `as`, IMO, but I guess arguments could be made to place it like
>>> `@foreach ($foo as $bar)` or `foreach @($foo as $bar)`.
>>>
>>>
>>> Regards,
>>> Aidan
>>>
>>> On 11 July 2017 at 20:06, Mark Shust <mark@shust.com> wrote:
>>>
>>>> Thanks for the great feedback.
>>>>
>>>> Based on the last mindset on keyword syntax, this comes to mind,
>>>> intended
>>>> to be used similarly to the 'use' keyword when used within the context
>>>> of a
>>>> closure:
>>>>
>>>> foreach ($foo as $bar) if (is_array) {
>>>> ...
>>>> }
>>>>
>>>>
>>>> I don't think this is a vast improvement over wrapping this within an
>>>> is_array check, however it does avoid the additional nest/wrapping. I
>>>> was
>>>> hoping for something that reads a bit more concisely or with a bit more
>>>> syntactical sugar than the above. I think this does read nicely though.
>>>>
>>>> Cheers,
>>>> Mark
>>>>
>>>> On Tue, Jul 11, 2017 at 1:50 PM Rowan Collins <rowan.collins@gmail.com>
>>>> wrote:
>>>>
>>>> > On 11 July 2017 16:02:18 BST, Mark Shust <mark@shust.com> wrote:
>>>> > >For a syntactic
>>>> > >sugar/improvement, this can be shorthand for executing the loop
>>>> instead
>>>> > >of
>>>> > >wrapping the block within an is_array check:
>>>> > >
>>>> > >
>>>> > ><?php
>>>> > >
>>>> > >$foo = "abc";
>>>> > >
>>>> > >foreach (??$foo as $bar) {
>>>> > >
>>>> > >  echo $bar;
>>>> > >
>>>> > >}
>>>> >
>>>> > Hi!
>>>> >
>>>> > I think there's definitely the start of a good idea here, but the
>>>> syntax
>>>> > you suggest doesn't read quite right. As has been pointed out, this
>>>> differs
>>>> > from existing features in two ways:
>>>> >
>>>> > - the special handling is for any non-iterable value, not just null or
>>>> > empty/falsey values, for which you could use $foo??[] and $foo?:[]
>>>> > respectively
>>>> > - the handling is to skip the loop, not loop once assigning $bar to
>>>> the
>>>> > scalar value, as would happen with (array)$foo
>>>> >
>>>> > The challenge, then, is to come up with some syntax that somehow
>>>> suggests
>>>> > these rules. The "??" is too much like the null coalesce, which would
>>>> be
>>>> > misleading.
>>>> >
>>>> > The only idea that immediately comes to mind is a keyword:
>>>> >
>>>> > foreach ifarray ($foo as $bar) {
>>>> >
>>>> > I can't say I'm that keen on that syntax, but maybe it will inspire
>>>> > someone else.
>>>> >
>>>> > Regards,
>>>> >
>>>> > --
>>>> > Rowan Collins
>>>> > [IMSoP]
>>>> >
>>>>
>>>
>>>
>

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