> On Apr 5, 2021, at 9:00 PM, Jesse Rushlow <j...@rushlow.dev> wrote: > > Sure thing - > > In Symfony's MakeBundle we have a command "php bin/console make:command". > This ultimately generates a "App\Console\XyzUserlandCommand::class" that > allows the developer to customize in order to perform some task within > their app. e.g. run persistence operations, generate a backup, etc.. > > What we do internally to generate that userland class is determine which > features to include by checking the PHP version, dependencies available, > etc.. As an example, when the user runs "make:command"; we check if they > have PHP 8 && if "class_exists(Symfony\.....\Attributes::class)" - if both > of those === true, we import the attribute class and generate the needed > attributes for the command. Otherwise we would fall back to using > annotations if the user is running PHP 7. Where I ran into trouble was the > Attributes::class (defines the attributes to be used in userland) utilized > constructor property promotion (which is a pretty sweet addition to 8 imo). > > Up to this point if it's possible, we generally pick a > class/interface/method that introduces new functionality (Symfony > feature/bugfix) and call one of the \*_exists(class/method/interface) > functions in a conditional to determine if we can indeed use that feature. > But because in this particular case the Attributes::class also uses > constructor property promotion, when calling > class_exists(Attributes::class) in PHP 7 we get: > > > ParseError: syntax error, unexpected 'public' (T_PUBLIC), expecting > variable (T_VARIABLE) > > The work around was to "$canUseAttributes = 80000 <= \PHP_VERSION_ID && \ > class_exists(AsCommand::class)" > > All is fine and well, but this in my opinion, this feels like bad mojo from > a developers standpoint. I must now need to be aware of the exact > implementation details of the object I'm checking before I can even check > if it exists or not. I would expect any of the \*_exists() to tell me if > the class/method/interface exists regardless of the implementation. My > first thought would be if the implementation is not compatible with the PHP > version some sort of \RuntimeException::class would be thrown by PHP. But > that is where my knowledge of PHP internals is disconnected from developing > software in PHP. > > I created a simple reproducer repo > https://github.com/rushlow-development/attribute-test (forgive the repo > name, it really has nothing to do with attributes.) and for an even simpler > example https://3v4l.org/4cMW4 > > I apologize in advance for the wall of text - but I'm curious if there is a > way to either improve our native functions, improve the docs, and/or create > new functions for use cases like this.
It is not clear to me exactly what you are asking for. It seems like your use-case exists when loading code in an older version of PHP that does not support newer features, right? If that is the case, the only "solution" — which is obviously a non-starter — is to update older versions of PHP to be able to gracefully fail when attempting to load a class designed for a newer version of PHP to use. OTOH if I misunderstand then can you clarify exactly what you are asking for? -Mike > > Thanks! > Jesse Rushlow > > On Mon, Apr 5, 2021 at 3:30 PM Rowan Tommins <rowan.coll...@gmail.com> > wrote: > >> On 05/04/2021 18:14, Jesse Rushlow wrote: >>> I was attempting to use class_exists(UsesPropertyPromotion::class) to >>> determine if an attribute implementation existed in order to generate a >> PHP >>> 8 appropriate class - else fall back to generating a PHP 7 appropriate >>> class. For context, this check was being written for Symfony's >> MakerBundle >>> which generates classes for Symfony projects. >> >> >> Hi Jesse, >> >> Can you explain the use case in a bit more detail, perhaps giving some >> example code you were hoping to write with class_exists()? >> >> I suspect there are other ways to achieve what you were trying to do, >> but don't want to confuse things if I've misunderstood the requirements. >> >> Regards, >> >> -- >> Rowan Tommins >> [IMSoP] >> >>
