[DependencyInjection] add ServiceSubscriberTrait #27077

kbond · 2018-04-27T15:07:21Z

Q	A
Branch?	master
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	#23898
License	MIT
Doc PR	symfony/symfony-docs#9809

This allows you to easily configure Service Subscribers with the following convention:

class MyService implements ServiceSubscriberInterface
{
    use ServiceSubscriberTrait;

    public function doSomething()
    {
        // $this->router() ...
    }

    private function router(): RouterInterface
    {
        return $this->container->get(__METHOD__);
    }
}

This also allows you to create helper traits like RouterAware, LoggerAware etc... and compose your services with them (not using __METHOD__ in traits because it doesn't behave as expected.).

trait LoggerAware
{
    private function logger(): LoggerInterface
    {
        return $this->container->get(__CLASS__.'::'.__FUNCTION__);
    }
}

trait RouterAware
{
    private function router(): RouterInterface
    {
        return $this->container->get(__CLASS__.'::'.__FUNCTION__);
    }
}

class MyService implements ServiceSubscriberInterface
{
    use ServiceSubscriberTrait, LoggerAware, RouterAware;

    public function doSomething()
    {
        // $this->router() ...
        // $this->logger() ...
    }
}

stof · 2018-04-27T15:13:00Z

src/Symfony/Bundle/FrameworkBundle/Resources/config/annotations.xml

@@ -13,6 +13,11 @@
                <!-- dummy arg to register class_exists as annotation loader only when required -->
                <argument type="service" id="annotations.dummy_registry" />
            </call>
+            <call method="addGlobalIgnoredName">
+                <argument>service</argument>
+                <!-- dummy arg to register class_exists as annotation loader only when required -->


no need to make multiple dummy registration

stof · 2018-04-27T15:14:57Z

src/Symfony/Component/DependencyInjection/ServiceSubscriberTrait.php

+
+            $returnType = $returnType->getName();
+
+            if (!class_exists($returnType) && !interface_exists($returnType)) {


the second call could avoid triggering the autoloader, as it was already triggered by the first one

Can you explain? I don't understand what should be done instead.

if (!class_exists($returnType) && !interface_exists($returnType, false)) {

As class_exists already triggered the autoloader, there is no need to trigger it for interfaces. If the interface exists, it will already have been loaded by the class_exists check.

I see, thanks!

nicolas-grekas

Cool, thank you for starting this!
I think we need additional logic to deal with inheritance (i.e. call the parent method if any)

nicolas-grekas · 2018-04-27T16:51:41Z

src/Symfony/Component/DependencyInjection/ServiceSubscriberTrait.php

+        $services = array();
+
+        foreach ((new \ReflectionClass(static::class))->getMethods() as $method) {
+            if (false === strpos($method->getDocComment(), '@service')) {


how would it look like if we were to remove this condition?
instead, we could just make all services optional ( $services[$method->getName()] = '?'.$returnType; )
I feel like it could work quite nicely in practice.

I tried this change and it seems to work but can't help thinking their may be side effects I can't think of...

One thing that comes to mind is developers wouldn't get immediate feedback if their services aren't wired correctly.

Thoughts?

Not having to declare anything creates a great experience.
About the error, I'm not sure how it would/should behave, we should try and figure out.

nicolas-grekas · 2018-04-27T16:52:16Z

src/Symfony/Component/DependencyInjection/ServiceSubscriberTrait.php

+
+            $returnType = $returnType->getName();
+
+            if (!class_exists($returnType) && !interface_exists($returnType, false)) {


this can also be removed if the map contains only optional services :)

nicolas-grekas · 2018-04-27T16:52:30Z

src/Symfony/Component/DependencyInjection/ServiceSubscriberTrait.php

+                continue;
+            }
+
+            $services[$method->getName()] = $returnType;


so: $services[$method->getName()] = '?'.$returnType;

nicolas-grekas · 2018-04-27T16:53:22Z

src/Symfony/Component/DependencyInjection/ServiceSubscriberTrait.php

+        $this->container = $container;
+    }
+
+    protected function service(string $id)


no need for this method, ppl should just have to write $this->container->get(__FUNCTION__);
(the property is private but is in the class' scope so one can access it)

What if there is a subclass that adds its own service methods?

maybe we should use $this->container->get(__METHOD__); instead?

But if $container is private, subclasses can't access it in their methods.

we don't care, do we? each such class would just have to use the trait (provided we add the logic to call the method on the parent)

Then we should use $this->service(__CLASS__, __FUNCTION__);, isn't it?

OR, we could make the trait work only with public and protected methods. Any preference? Does it make sense to use a private method for these anyway? (could be, you'll tell me what you think about this :) )

Why can't we just use __FUNCTION__ as I had originally?

using function works when used in public/protected methods, but might break when mixed with private methods: a private method with same name but different return type can be defined in a parent class. When the parent will call its private method, it will get the service that was injected for the child definition. And this can just break...

Understood.

Using $this->service(__CLASS__, __FUNCTION__); would get my vote then.

Cool. I updated my proposal above, it should be ok so you can borrow it. For the changelog, this should be in the 4.2 section. With a few tests, I think we might be good :)

kbond · 2018-05-02T14:52:13Z

I have pushed the changes @nicolas-grekas and I have discussed and updated the PR description. If this looks good, I'll add some tests.

nicolas-grekas · 2018-05-02T15:23:06Z

Looks good to me :)

lyrixx · 2018-05-02T15:40:41Z

Even if the implementation is good, I don't like this feature.
It adds another way of doing things without really reducing the line of code needed.

And this is going to be accepted, it will needs some tests

nicolas-grekas · 2018-05-02T23:31:00Z

@lyrixx I didn't like autowiring first. Now I like it. Might be the same for you here. About tests, we agree, see mentions of it above :) Another way of doing things? For sure, but there is a huge benefit for DX: enabling autocompletion (as described in linked issue #23898). And this doesn't leak to the outside world: it stays a pure implementation detail. Definitely worth it IMHO.

nicolas-grekas · 2018-05-02T23:32:16Z

src/Symfony/Component/DependencyInjection/ServiceSubscriberTrait.php

+use Psr\Container\ContainerInterface;
+
+/**
+ * @author Kevin Bond <[email protected]>


could be worth some notes in the docblock

nicolas-grekas

getDeclaringClass should be used instead of getProrotype, my bad

nicolas-grekas · 2018-05-06T17:08:52Z

src/Symfony/Component/DependencyInjection/ServiceSubscriberTrait.php

+            }
+
+            try {
+                $method = $method->getPrototype();


the entire try/catch should be removed actually

nicolas-grekas · 2018-05-06T17:09:03Z

src/Symfony/Component/DependencyInjection/ServiceSubscriberTrait.php

+            }
+
+            if (($returnType = $method->getReturnType()) && !$returnType->isBuiltin()) {
+                $services[$method->class.'::'.$method->name] = $returnType->getName();


$services[$method->getDeclaringClass()->name.'::'.$method->name] = '?'.$returnType->getName();

kbond · 2018-05-10T14:48:16Z

I added a happy path test.

nicolas-grekas · 2018-05-10T15:35:52Z

src/Symfony/Component/DependencyInjection/ServiceSubscriberTrait.php

+                continue;
+            }
+
+            if (($returnType = $method->getReturnType()) && !$returnType->isBuiltin()) {


I feel like we should be even more strict and not wire methods from parents, as they should be the one declaring their deps.
$method->getDeclaringClass() === self::class should be added first in the "if" (then we can use self::class also on the next line.)

nicolas-grekas · 2018-05-10T16:03:02Z

src/Symfony/Component/DependencyInjection/ServiceSubscriberTrait.php

+    public function setContainer(ContainerInterface $container): void
+    {
+        if (\is_callable(array('parent', __FUNCTION__))) {
+            parent::setContainer($container);


In order to be compatible with AbstractController, we should return the return value of the parent (thus set the property before this block and remove the void on the signature.)

If there is no parent should I return something?

I don't think so.

nicolas-grekas · 2018-05-10T18:09:19Z

Would be nice to have a few more test cases covering:

that methods from parents are ignored
that methods from children are ignored
that parent getSubscribedServices/setContainer methods are called

Otherwise, it looks great to me, thank you!

kbond · 2018-05-10T18:45:42Z

I have added the requested tests.

nicolas-grekas

I like it :)

lyrixx · 2018-05-28T12:15:50Z

Just one question, insteand of writing return $this->service(__CLASS__, __FUNCTION__);,
Can't we play with the backtrace to get __CLASS__, __FUNCTION__ Automatically ?
Or at least __METHOD__ ?

nicolas-grekas · 2018-05-28T12:52:21Z

can't we play with the backtrace to get __CLASS__, __FUNCTION__

this is a runtime call, that'd be too slow

least __METHOD__

we discussed about it in #27077 (comment)

actually, I think removing the "service" helper might be nice.
Ppl would have to write $this->container->get(__METHOD__) instead of the current $this->service(__CLASS__, __FUNCTION__). I like it because it means one less indirection. For traits authors, they'd have to write $this->container->get(__CLASS__.'::'.__FUNCTION__). But their pb I think, that's a small overhead for an uncommon case.

@kbond ok for you?

kbond · 2018-05-30T20:33:35Z

My only hesitation is it makes creating composable traits (which I think/hope will not be uncommon) not as intuitive. I can see people putting $this->container->get(__METHOD__) in their trait methods and being confused as to why it isn't working - I was.

That being said, if composable traits aren't common, it is easier to do $this->container->get(__METHOD__).

Seems prudent to keep it simple now and add a service() helper later if it becomes problematic. I will update the PR.

kbond · 2018-05-31T13:18:47Z

I removed the service() method and updated docs and this PR description.

nicolas-grekas · 2018-06-04T19:56:37Z

Thank you @kbond.

This PR was squashed before being merged into the 4.2-dev branch (closes #27077). Discussion ---------- [DependencyInjection] add ServiceSubscriberTrait | Q | A | ------------- | --- | Branch? | master | Bug fix? | no | New feature? | yes | BC breaks? | no | Deprecations? | no | Tests pass? | yes | Fixed tickets | #23898 | License | MIT | Doc PR | symfony/symfony-docs#9809 This allows you to easily configure Service Subscribers with the following convention: ```php class MyService implements ServiceSubscriberInterface { use ServiceSubscriberTrait; public function doSomething() { // $this->router() ... } private function router(): RouterInterface { return $this->container->get(__METHOD__); } } ``` This also allows you to create helper traits like `RouterAware`, `LoggerAware` etc... and compose your services with them (*not* using `__METHOD__` in traits because it doesn't behave as expected.). ```php trait LoggerAware { private function logger(): LoggerInterface { return $this->container->get(__CLASS__.'::'.__FUNCTION__); } } ``` ```php trait RouterAware { private function router(): RouterInterface { return $this->container->get(__CLASS__.'::'.__FUNCTION__); } } ``` ```php class MyService implements ServiceSubscriberInterface { use ServiceSubscriberTrait, LoggerAware, RouterAware; public function doSomething() { // $this->router() ... // $this->logger() ... } } ``` Commits ------- 238e793 [DependencyInjection] add ServiceSubscriberTrait

…ond) This PR was merged into the master branch. Discussion ---------- [DependencyInjection] Document ServiceSubscriberTrait Documentation for symfony/symfony#27077 Commits ------- b0ac3a4 document ServiceSubscriberTrait

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nicolas-grekas changed the title ~~[RFC][DependencyInjection] add ServiceSubscriberTrait~~ [DependencyInjection] add ServiceSubscriberTrait May 10, 2018

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[DependencyInjection] Document ServiceSubscriberTrait symfony/symfony-docs#9809

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[DependencyInjection] add ServiceSubscriberTrait

238e793

nicolas-grekas merged commit 238e793 into symfony:master Jun 4, 2018

kbond deleted the service-subscriber branch June 4, 2018 19:58

nicolas-grekas modified the milestones: next, 4.2 Nov 1, 2018

This was referenced Nov 3, 2018

Release v4.2.0-BETA1 #29072

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Release v4.2.0-BETA1 #29073

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m-vo mentioned this pull request Jun 28, 2021

Introduce recorded migrations contao/contao#3108

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kbond mentioned this pull request Jul 21, 2021

[DependencyInjection] ServiceSubscriberTrait does not allow non-service "getter" methods #42217

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		$returnType = $returnType->getName();

		if (!class_exists($returnType) && !interface_exists($returnType)) {

[DependencyInjection] add ServiceSubscriberTrait #27077

[DependencyInjection] add ServiceSubscriberTrait #27077

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