>
> Using the container for configuration is not (imho) the purpose of 
> containers and makes it harder to standardize on using FQCN for container 
> identifiers.


I don't think it's limited to configuration. You'd have the same 
(non-)issue with config-less containers.

Matthieu
 

> On Sat, Mar 3, 2018, 15:18 Oscar Otero <oscar...@gmail.com <javascript:>> 
> wrote:
>
>> To me, the problem with these proposals is they have different 
>> responsabilities in the same class. A ServiceProvider implementation 
>> includes the callables to create instances of different services, defines 
>> the key used to store each of these services and even include two methods: 
>> one to get factories and other for extensions, so in many times you have to 
>> create a method returning an empty array (see 
>> https://github.com/container-interop/service-provider/issues/43), 
>> (Interface segregation principle).
>>
>> I proposed a different approach (
>> https://github.com/container-interop/service-provider/issues/45) 
>> consisting in creating a factory for each service. The proposal is just a 
>> sketch to illustrate the main concept (each object has just one 
>> responsabiity: create a service) and surely can be improved.
>>
>>
>>
>> El 3 mar 2018, a las 14:07, David Négrier <david....@gmail.com 
>> <javascript:>> escribió:
>>
>> To build upon Larry's answer, the container does not only contains 
>> services. It knows how to build them.
>>
>> If we ended up "setting" in a container every service, well first... we 
>> could use arrays instead of containers :) and then, the performance of the 
>> container would degrade proportionally to the number of entries in the 
>> container. You would have to instantiate and store every service on every 
>> request, even if the service does not end up being called. So basically, 
>> the bigest your application, the slowest.
>>
>> This is why both proposals carefully avoid the use of a "set" method.
>>
>> ++
>> David.
>>
>>
>> Le vendredi 2 mars 2018 23:02:49 UTC+1, Larry Garfield a écrit :
>>>
>>> The reason a simple set() won't work is that the "thing" put into the 
>>> container is generally not a value but instructions for how to produce a 
>>> value 
>>> on-demand, and the value is typically a service object.  How to encode 
>>> "here's 
>>> how to build the thing" is the main question to answer. 
>>>
>>> --Larry Garfield 
>>>
>>> On Friday, March 2, 2018 1:18:32 PM CST David Lundgren wrote: 
>>> > If the problem to solve is "what's a common way to put things in a 
>>> > container?" wouldn't the simplest solution be a `set($id, $value)` 
>>> method 
>>> > on the container? 
>>> > 
>>> > Most container implementations already have a method of this sort. 
>>> While a 
>>> > few have shared/concrete/protected concepts baked in, they could make 
>>> > separate methods for changing it  based on the $id. 
>>> > 
>>> > Dave 
>>> > 
>>> > On Thursday, March 1, 2018 at 11:16:29 AM UTC-6, David Négrier wrote: 
>>> > > Hey list, 
>>> > > 
>>> > > We are still in the process of forming a working group regarding a 
>>> Service 
>>> > > provider PSR. 
>>> > > 
>>> > > I've had the chance to speak about this with several Symfony 
>>> contributors, 
>>> > > and while discussing about this idea, Nicolas Grekas 
>>> > > <https://github.com/nicolas-grekas/> (from Symfony) came up with an 
>>> > > alternative proposal. It's about having many containers working 
>>> together, 
>>> > > with a slightly different scope. First of all, I'd like to thank 
>>> Nicolas 
>>> > > for the time he is investing in researching this issue, and for all 
>>> the 
>>> > > feedback. We talked about his idea with Matthieu Napoli 
>>> > > <https://github.com/mnapoli/> and Larry Garfield 
>>> > > <https://github.com/crell> at the Paris ForumPHP in November. I'm 
>>> now 
>>> > > sharing this conversation with you. 
>>> > > 
>>> > > I put this in a blog article that you can find here: 
>>> > >    
>>> https://thecodingmachine.io/psr-11-scope-of-universal-service-providers 
>>> > > 
>>> > > I'm reposting the content of the article here, since it's directly 
>>> related 
>>> > > to PHP-FIG concerns. It's a bit long, but the topic is worth it :) 
>>> > > 
>>> > > Stated goal 
>>> > > 
>>> > > Each framework has it's own custom package format (bundles, packages,
>>>  
>>> > > modules, etc...). What these package formats are doing is essentially
>>>  
>>> > > always the same. They are used to put things in a container. 
>>> > > 
>>> > > If the PHP-FIG could come up with a unique package format that could 
>>> be 
>>> > > supported by all frameworks, package developers could truly write 
>>> classes 
>>> > > that can be used in any framework more easily. 
>>> > > 
>>> > > Hence, the stated goal of this PSR (let's call it PSR-X since it 
>>> does not 
>>> > > have a number yet) is to find a common way to *put things in a 
>>> container*. 
>>> > > 
>>> > > We (the container-interop group) have been working on this for quite 
>>> some 
>>> > > time and have come up with a solution that needs to be turned into a 
>>> PSR 
>>> > > <https://github.com/container-interop/service-provider/>. The idea 
>>> is to 
>>> > > build generic service providers. 
>>> > > 
>>> > > 
>>> > > Current proposal 
>>> > > 
>>> > > The current proposal is named container-interop/service-provider 
>>> > > <https://github.com/container-interop/service-provider/>. In this 
>>> > > proposal, we create a ServiceProviderInterface interface that 
>>> exposes a 
>>> > > set of *factories*. 
>>> > > 
>>> > > 
>>> > > class MyServiceProvider implements ServiceProviderInterface{ 
>>> > > 
>>> > >     public function getFactories() 
>>> > >     { 
>>> > >     
>>> > >         return [ 
>>> > >         
>>> > >             'my_service' => function(ContainerInterface $container) :
>>>  
>>> > >             MyService { 
>>> > >             
>>> > >                 $dependency = $container->get('my_other_service'); 
>>> > >                 return new MyService($dependency); 
>>> > >             
>>> > >             } 
>>> > >         
>>> > >         ]; 
>>> > >     
>>> > >     } 
>>> > >     
>>> > >     // ... 
>>> > > 
>>> > > } 
>>> > > 
>>> > > 
>>> > > In the example above, the 'my_service' service can be created by the
>>>  
>>> > > container by executing the factory (the anonymous function). 
>>> > > 
>>> > > Additionally, the ServiceProviderInterface let's you *modify* 
>>> existing 
>>> > > services stored in the container. 
>>> > > 
>>> > > 
>>> > > class MyServiceProvider implements ServiceProviderInterface{ 
>>> > > 
>>> > >     // ... 
>>> > >     
>>> > >     public function getExtensions() 
>>> > >     { 
>>> > >     
>>> > >         return [ 
>>> > >         
>>> > >             Twig_Environment::class => function(ContainerInterface 
>>> > >             $container, Twig_Environment $twig) : Twig_Environment 
>>> {>             
>>> > >                 $twig->addExtension($container->get('my_extension'));
>>>  
>>> > >                 return $twig; 
>>> > >             
>>> > >             } 
>>> > >         
>>> > >         ]; 
>>> > >     
>>> > >     } 
>>> > > 
>>> > > } 
>>> > > 
>>> > > 
>>> > > In the example above, the service named "Twig_Environment" is 
>>> modified. We 
>>> > > register a new twig extension in it. This is very powerful. This can 
>>> be 
>>> > > used to create arrays and add elements to them, or this can be used 
>>> to 
>>> > > decorate an existing service (using the decorator pattern). Overall, 
>>> this 
>>> > > gives a lot of power to the service provider. 
>>> > > 
>>> > > Right now, this interface has been tested. It has adapters in 
>>> Symfony, 
>>> > > Laravel, and there is a Pimple fork named Simplex that is also 
>>> > > implementing 
>>> > > it. You can view the complete list of implementations here 
>>> > > <
>>> https://github.com/container-interop/service-provider#compatible-projects
>>>  
>>> > > > 
>>> > > . 
>>> > > 
>>> > > 
>>> > > The alternative proposal 
>>> > > 
>>> > > Nicolas Grekas and the Symfony team came up with another proposal 
>>> > > <https://github.com/symfony/symfony/pull/25707>. 
>>> > > 
>>> > > Rather than standardizing service providers, he proposes that each 
>>> package 
>>> > > could provide it's own container. The container would have an 
>>> interface to 
>>> > > expose a list of services to your application's container. 
>>> > > 
>>> > > The proposal goes like this: 
>>> > > 
>>> > > 
>>> > > interface ServiceProviderInterface extends ContainerInterface{ 
>>> > > 
>>> > >     /** 
>>> > >     
>>> > >      * Returns an associative array of service types keyed by names 
>>> > >      provided by this object. * 
>>> > >      * Examples: 
>>> > >      * 
>>> > >      *  * array('logger' => 'Psr\Log\LoggerInterface') means the 
>>> object 
>>> > >      provides service implementing Psr\Log\LoggerInterface *    under
>>>  
>>> > >      "logger" name 
>>> > >      *  * array('foo' => '?') means that object provides service of 
>>> > >      unknown type under 'foo' name *  * array('bar' => '?Bar\Baz') 
>>> means 
>>> > >      that object provides service implementing Bar\Baz or null under
>>>  
>>> > >      'bar' name * 
>>> > >      * @return string[] The provided service types, keyed by service 
>>> names 
>>> > >      */ 
>>> > >     
>>> > >     public function getProvidedServices(): array; 
>>> > > 
>>> > > } 
>>> > > 
>>> > > 
>>> > > Notice how the ServiceProviderInterface extends the PSR-11 
>>> > > ContainerInterface <https://www.php-fig.org/psr/psr-11/>. 
>>> > > 
>>> > > Here, there is a single function getProvidedServices that provides 
>>> the 
>>> > > names of the provided services as keys, along the type of the 
>>> service as 
>>> > > values. 
>>> > > 
>>> > > When your application's container is asked for a service that is 
>>> part of a 
>>> > > "service provider", it would simply call the get method of the 
>>> service 
>>> > > provider (since a service provider IS a container) and retrieve the 
>>> > > service. 
>>> > > 
>>> > > There is no way for a service provider to modify services in the 
>>> > > application's container (this is a design decision). 
>>> > > 
>>> > > While talking about this interface, we also mentioned another 
>>> interface. A 
>>> > > service provider can need dependencies stored in another container. 
>>> It 
>>> > > could therefore publish the list of services it is expecting to find 
>>> in 
>>> > > the 
>>> > > main container. Therefore, Nicolas proposed an additional interface:
>>>  
>>> > > ServiceSubscriberInterface, providing a getSubscribedServices method.
>>>  
>>> > > 
>>> > > 
>>> > > class TwigContainer implement ServiceProviderInterface, 
>>> > > ContainerInterface, ServiceSubscriberInterface {> 
>>> > >     //... 
>>> > >     
>>> > >     public function getSubscribedServices() 
>>> > >     { 
>>> > >     
>>> > >         // The TwigContainer needs 2 services to be defined: 
>>> > >         //  - "debug" (this is an optionnal bool value) 
>>> > >         //  - "twig_extensions" (this is an optionnal array of 
>>> objects 
>>> > >         implementing TwigExtentionInterface) return [ 
>>> > >         
>>> > >             'debug' => '?bool', 
>>> > >             'twig_extensions' => 
>>> '?'.TwigExtentionInterface::class.'[]', 
>>> > >         
>>> > >         ]; 
>>> > >     
>>> > >     } 
>>> > > 
>>> > > } 
>>> > > 
>>> > > 
>>> > > Notice that the 2 interfaces can be considered independently. The 
>>> > > ServiceSubscriberInterface allows to add an additional check at 
>>> container 
>>> > > build time (vs getting a runtime exception if a service is lacking a
>>>  
>>> > > container entry or if the provided container entry is of the wrong 
>>> type). 
>>> > > 
>>> > > 
>>> > > Comparing of the 2 proposalsRegarding performance 
>>> > > 
>>> > > Regarding performance, the 2 proposals have very different 
>>> properties. 
>>> > > 
>>> > > 
>>> > > *In container-interop/service-providers*: 
>>> > > 
>>> > > The service provider is largely considered as *dumb*. It is *the 
>>> > > responsibility of the container* to optimize the calls. 
>>> > > 
>>> > > Actually, it is possible to get excellent performances if the service
>>>  
>>> > > provider is providing the factories as public static functions. 
>>> > > 
>>> > > class MyServiceProvider implements ServiceProviderInterface{ 
>>> > > 
>>> > >     public function getFactories() 
>>> > >     { 
>>> > >     
>>> > >         return [ 
>>> > >         
>>> > >             Twig_Environment::class => [ self::class, 'createTwig' ]
>>>  
>>> > >         
>>> > >         ]; 
>>> > >     
>>> > >     } 
>>> > >     
>>> > >     public static function createTwig(ContainerInterface $container,
>>>  
>>> > >     Twig_Environment $twig) : Twig_Environment {>     
>>> > >         $twig->addExtension($container->get('my_extension')); 
>>> > >         return $twig; 
>>> > >     
>>> > >     } 
>>> > >     
>>> > >     // ... 
>>> > > 
>>> > > } 
>>> > > 
>>> > > In this case, a compiled container could directly call the factory, 
>>> > > without having to instantiate the service provider class nor call the
>>>  
>>> > > getFactories method. This is definitely the best performance you can 
>>> get 
>>> > > (but is still to the good-will of the service-provider author that 
>>> must 
>>> > > use public static methods instead of closures). 
>>> > > 
>>> > > 
>>> > > *In Symfony's proposal*: 
>>> > > 
>>> > > The service provider is an actual container. *The service provider is
>>>  
>>> > > therefore in charge of the performance of delivered services*. 
>>> > > 
>>> > > It probably cannot beat the direct call to a public static function 
>>> > > (since you have to call at least the service provider constructor 
>>> and the 
>>> > > get function of the service provider), but can still be quite 
>>> optimized. 
>>> > > The important part is that the performance is delegated to the 
>>> service 
>>> > > provider. 
>>> > > 
>>> > > Dealing with service names 
>>> > > 
>>> > > *In container-interop/service-providers*: 
>>> > > 
>>> > > The idea is that service providers should respect some kind of 
>>> convention. 
>>> > > 
>>> > > If you are writing a service provider for Monolog, the service 
>>> creating 
>>> > > the Monolog\Logger class should be named Monolog\Logger. This will 
>>> allow 
>>> > > containers using *auto-wiring* to automatically find the service. 
>>> > > 
>>> > > Additionally, you can create an *alias* for your service on the 
>>> > > Psr\Log\LoggerInterface, if you want to auto-wire the 
>>> LoggerInterface to 
>>> > > the Monolog\Logger service. 
>>> > > 
>>> > > The code would therefore look like this: 
>>> > > 
>>> > > 
>>> > > class MonologServiceProvider implements ServiceProviderInterface{ 
>>> > > 
>>> > >     public function getFactories() 
>>> > >     { 
>>> > >     
>>> > >         return [ 
>>> > >         
>>> > >             \Psr\Log\LoggerInterface::class => [ self::class, 
>>> > >             'createAlias' ], 
>>> > >             \Monolog\Logger::class => [ self::class, 'createLogger' 
>>> ], 
>>> > >         
>>> > >         ]; 
>>> > >     
>>> > >     } 
>>> > >     
>>> > >     public static function createLogger(): \Monolog\Logger 
>>> > >     { 
>>> > >     
>>> > >         return new \Monolog\Logger('default'); 
>>> > >     
>>> > >     } 
>>> > >     
>>> > >     public static function createAlias(ContainerInterface 
>>> $container): 
>>> > >     \Monolog\Logger { 
>>> > >     
>>> > >         return $container->get('\Monolog\Logger'); 
>>> > >     
>>> > >     } 
>>> > >     
>>> > >     // ... 
>>> > > 
>>> > > } 
>>> > > 
>>> > > 
>>> > > *In Symfony's proposal*: 
>>> > > 
>>> > > I must admit I'm not 100% clear on Nicolas thought here. There are 
>>> really 
>>> > > 2 solutions. Either we adopt a convention (just like with 
>>> > > container-interop/service-provider), either we can decide that the 
>>> > > container can be "clever". After all, using the getProvidedServices 
>>> > > class, a container can know the type of all provided services, so if 
>>> it 
>>> > > could decide to autowire them by its own. 
>>> > > 
>>> > > For instance, if a call to getProvidedServices returns: 
>>> > > 
>>> > > [ 
>>> > > 
>>> > >     'logger' => '\Monolog\Logger' 
>>> > > 
>>> > > ] 
>>> > > 
>>> > > the container could decide on its own that the 'logger' service is a 
>>> good 
>>> > > fit to auto-wire '\Monolog\Logger'. 
>>> > > 
>>> > > At this stage, the decision is delegated to the container. The 
>>> service 
>>> > > provider is more "dumb". It does not know and does not decide what 
>>> gets 
>>> > > auto-wired. The container does (this means there is probably some 
>>> > > configuration required in the container). 
>>> > > 
>>> > > Dealing with list of services 
>>> > > 
>>> > > It is pretty common to want to add a service to a list of services. 
>>> In 
>>> > > containers, this is usually done by using "tags". None of the 2 
>>> proposals 
>>> > > supports the notion of tags directly. But both have workarounds. 
>>> > > 
>>> > > 
>>> > > *In container-interop/service-providers*: 
>>> > > 
>>> > > The idea is to create an entry in the container that is actually an 
>>> array 
>>> > > of services. Each service provider can then modify the array to 
>>> register 
>>> > > its own service in it. 
>>> > > 
>>> > > class MonologHandlerServiceProvider implements 
>>> ServiceProviderInterface{ 
>>> > > 
>>> > >     // ... 
>>> > >     
>>> > >     public function getExtensions() 
>>> > >     { 
>>> > >     
>>> > >         return [ 
>>> > >         
>>> > >             HandlerInterface::class.'[]' => 
>>> function(ContainerInterface 
>>> > >             $container, array $handlers = []) : array {>            
>>>  
>>> > >                 $handlers[] = new MyMonologHandler(); 
>>> > >                 return $handlers; 
>>> > >             
>>> > >             } 
>>> > >         
>>> > >         ]; 
>>> > >     
>>> > >     } 
>>> > > 
>>> > > } 
>>> > > 
>>> > > 
>>> > > *In Symfony's proposal*: 
>>> > > 
>>> > > The PR does not state it, but we could imagine allowing types with 
>>> '[]' at 
>>> > > the end. 
>>> > > 
>>> > > For instance, if a call to getProvidedServices returns: 
>>> > > 
>>> > > [ 
>>> > > 
>>> > >     'monologHandlers' => HandlerInterface::class.'[]' 
>>> > > 
>>> > > ] 
>>> > > 
>>> > > then the container might decide to automatically append the services
>>>  
>>> > > returned by 'monologHandlers' to services with the same name in the 
>>> main 
>>> > > container. 
>>> > > 
>>> > > Said otherwise, the container calls get('monologHandlers') on all the
>>>  
>>> > > service providers and concatenates those. 
>>> > > 
>>> > > Dealing with list of services with priorities 
>>> > > 
>>> > > Sometimes, you are adding a service in a list that must be ordered. 
>>> > > 
>>> > > Let's take an example. You just wrote a PSR-15 middleware that is an 
>>> error 
>>> > > handler (like the Whoops middleware 
>>> > > <https://github.com/middlewares/whoops>). This middleware must 
>>> absolutely 
>>> > > be the first to be executed in the list of middlewares (because it 
>>> will 
>>> > > catch any exception that might be thrown by other middlewares). 
>>> > > 
>>> > > Some containers allow to tag with priorities. But we don't have this
>>>  
>>> > > notion in our interfaces. 
>>> > > 
>>> > > How can we deal with that? 
>>> > > Do we need this? Discussing with Matthieu Napoli, I know that 
>>> Matthieu 
>>> > > thinks this can be out of scope of the PSR. In Matthieu's view, it 
>>> is not 
>>> > > the responsibility of the service provider to decide where a service 
>>> is 
>>> > > inserted in a list. I personnally feel this is quite an important 
>>> feature. 
>>> > > An error handling middleware knows it must be at the very beginning 
>>> so I 
>>> > > think we (the service providers authors) should do all what we can 
>>> to help 
>>> > > the developer using our middleware to put it at the right spot. For 
>>> the 
>>> > > author of the Whoops middleware service provider, it is quite 
>>> obvious that 
>>> > > the middleware must go first. For the average PHP developer that is 
>>> not an 
>>> > > expert in middleware architectures, it might be far less obvious. 
>>> > > 
>>> > > 
>>> > > *In container-interop/service-providers*: 
>>> > > 
>>> > > The idea is to create an entry in the container that is a priority 
>>> queue. 
>>> > > For instance, PHP has the great \SplPriorityQueue. 
>>> > > 
>>> > > class WhoopsMiddlewareServiceProvider implements 
>>> ServiceProviderInterface{ 
>>> > > 
>>> > >     // ... 
>>> > >     
>>> > >     public function getExtensions() 
>>> > >     { 
>>> > >     
>>> > >         return [ 
>>> > >         
>>> > >             'middlewareList' => function(ContainerInterface 
>>> $container, 
>>> > >             \SplPriorityQueue $middlewares) : \SplPriorityQueue {>   
>>>           
>>> > >                 $middlewares->insert(new WhoopsMiddleware(), -9999);
>>>  
>>> > >                 // Note: we should replace the -9999 by a constant 
>>> like 
>>> > >                 MiddlewarePriorities::VERY_EARLY return $middlewares;
>>>  
>>> > >             
>>> > >             } 
>>> > >         
>>> > >         ]; 
>>> > >     
>>> > >     } 
>>> > > 
>>> > > } 
>>> > > 
>>> > > 
>>> > > *In Symfony's proposal*: 
>>> > > 
>>> > > How to deal with this in Symfony's proposal is quite unclear to me. 
>>> > > 
>>> > > We could decide this is out of scope. 
>>> > > 
>>> > > We could also decide that we have many unsorted list, like 
>>> > > 'earlyMiddlewares', 'utilityMiddlewares', 'routerMiddlewares'... 
>>> that are 
>>> > > concatenated by the middleware service provider and fed to the 
>>> middleware 
>>> > > pipe. 
>>> > > 
>>> > > Miscellaneous 1: introspection 
>>> > > 
>>> > > Symfony's proposal has 2 wonderful features that 
>>> > > container-interop/service-provider does not have. They are not 
>>> directly 
>>> > > 
>>> > > necessary to our stated goal, but are quite nice: 
>>> > >    - the ServiceProviderInterface is actually an introspection 
>>> interface 
>>> > >    into any container implementing it. This gives us a lot of room to
>>>  
>>> > >    write 
>>> > >    cross-framework tools that can scan containers and analyze them. 
>>> Pretty 
>>> > >    cool. 
>>> > >    - the fact that a service provider can publish the list of 
>>> > >    dependencies it needs (the ServiceSubscriberInterface) is in my 
>>> > >    opinion a very good idea. A service provider offers some entries 
>>> but 
>>> > >    can 
>>> > >     
>>> > >    also require some entries. By publishing its requirements, we get:
>>>  
>>> > >       - automated documentation 
>>> > >       - the possibility to do static analysis 
>>> > >       - the possibility to write tool chains that help the developer 
>>> set 
>>> > >       up service providers (think about a huge online database of all
>>>  
>>> > >       service 
>>> > >       providers available on Packagist with what they offer and what 
>>> they 
>>> > >       require 
>>> > >       
>>> > >       :) ) 
>>> > > 
>>> > > Miscellaneous 2: factory services 
>>> > > 
>>> > > PSR-11 recommends that 2 successive calls to get should return the 
>>> same 
>>> > > entry: 
>>> > > 
>>> > > Two successive calls to get with the same identifier SHOULD return 
>>> the 
>>> > > same value. 
>>> > > 
>>> > > Indeed, a container contains services. It should not act as a 
>>> factory. 
>>> > > Yet, it does not forbid containers to act as a factory (we used 
>>> "SHOULD" 
>>> > > and not "MUST" in PSR-11). *container-interop/service-provider* on 
>>> the 
>>> > > other end is very explicit. The service provider provides factories, 
>>> and 
>>> > > the container MUST cache the provided service. So for services 
>>> provided by 
>>> > > *container-interop/service-provider*, 2 successive calls to the 
>>> container 
>>> > > MUST return the same object. I don't see this as a problem, rather 
>>> as a 
>>> > > feature. Yet, with Symfony's proposal, since calls to "get" are 
>>> delegated 
>>> > > to the service provider (that is a container itself), we could write 
>>> a 
>>> > > service provider that provides a new service on each call to get. 
>>> > > Symfony's 
>>> > > proposal is more flexible in that regard. 
>>> > > 
>>> > > Summary / TL;DR 
>>> > > 
>>> > > That table below summarizes the differences between the 2 proposals:
>>>  
>>> > > 
>>> > > 
>>> > > 
>>> > > *container-interop* *Symfony* 
>>> > > Performance Container is in charge Service provider is in charge 
>>> > > Service names By convention Can be deduced from types 
>>> > > Static analysis No Possible 
>>> > > Modifying services Yes (powerful service providers) No (dumb service
>>>  
>>> > > providers) 
>>> > > Tagged services Yes, via modified arrays Yes 
>>> > > Tagged services with priorities Yes, via modified SplPriorityQueues 
>>> No 
>>> > > (out of scope?) 
>>> > > 
>>> > > 
>>> > > My thoughts 
>>> > > This section highlights my current opinions. Others might completely
>>>  
>>> > > disagree and I think it is important we have a discussion about what 
>>> we 
>>> > > want to achieve. 
>>> > > 
>>> > > By standardizing service providers, we are shifting the 
>>> responsibility of 
>>> > > writing the "glue code" from the framework developer to the package 
>>> > > developer. For instance, if you consider Doctrine ORM, it is likely 
>>> that 
>>> > > the Doctrine service provider would be written by the Doctrine 
>>> authors 
>>> > > (rather than the Symfony/Zend developers). It is therefore in my 
>>> opinion 
>>> > > important to empower the package developer with an interface that 
>>> gives 
>>> > > him/her some control over what gets stored in the container. 
>>> > > 
>>> > > 
>>> > > Existing packaging systems (like Symfony bundles or Laravel service 
>>> > > providers) have already this capability and I believe we should aim 
>>> for 
>>> > > this in the PSR. 
>>> > > 
>>> > > 
>>> > > Taking the "PSR-15 Whoops middleware" example, it is for me very 
>>> important 
>>> > > that the service provider author can decide where in the middleware 
>>> pipe 
>>> > > the middleware is added. This means being able to add a service at a 
>>> given 
>>> > > position in a list (or having tags with priorities). This, in my 
>>> opinion, 
>>> > > should be in the scope of the PSR. 
>>> > > 
>>> > > Said otherwise, while registering the service provider in the 
>>> container, 
>>> > > the user should be able to write: 
>>> > > 
>>> > > 
>>> > > $container->register(new WhoopsMiddlewareServiceProvider()); 
>>> > > 
>>> > > 
>>> > > instead of something like: 
>>> > > 
>>> > > 
>>> > > $container->register(new WhoopsMiddlewareServiceProvider(), [ 
>>> > > 
>>> > >     'priority' => [ 
>>> > >     
>>> > >         WhoopsMiddleware::class => -999 
>>> > >     
>>> > >     ] 
>>> > > 
>>> > > ]); 
>>> > > 
>>> > > 
>>> > > In this regard, I feel the *container-interop/service-provider* 
>>> proposal 
>>> > > is better suited (because it allows to modify an existing service 
>>> and that 
>>> > > is all we need). 
>>> > > 
>>> > > That being said, the proposal of Nicolas has plenty of advantages I 
>>> can 
>>> > > 
>>> > > also very well see: 
>>> > >    - container introspection 
>>> > >    - better maintainability/documentation through better tooling 
>>> > > 
>>> > > I have a gut feeling that there is something that can be done to 
>>> merge the 
>>> > > 2 proposals and get the best of both worlds. Or maybe we can have 
>>> the 2 
>>> > > proposals live side by side (one for service providers and the other 
>>> for 
>>> > > container introspection?) 
>>> > > 
>>> > > 
>>> > > What do you think? 
>>> > > 
>>> > > What should be the scope of the PSR? 
>>> > > 
>>> > > For you, is it important to give service provider some control over 
>>> the 
>>> > > container or should they be "dumb" and just provide instances (with 
>>> the 
>>> > > controller keeping the control on how the instances are managed)? 
>>> > > 
>>> > > 
>>> > > ++ 
>>> > > 
>>> > > David 
>>> > > 
>>> > > Twitter: @david_negrier 
>>> > > 
>>> > > Github: @moufmouf 
>>>
>>>
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> Woody Gilk
> http://about.me/shadowhand
>

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