feature #36599 [HttpKernel] make kernels implementing WarmableInterface be part of the cache warmup stage (nicolas-grekas)

This PR was merged into the 5.1-dev branch.

Discussion
----------

[HttpKernel] make kernels implementing `WarmableInterface` be part of the cache warmup stage

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

This allows your kernel to return extra classes to preload also (which was my main motivation for creating this PR actually.)

```php
// ...
use Symfony\Component\HttpKernel\CacheWarmer\WarmableInterface;
// ...

class Kernel ... implements ..., WarmableInterface
{
    // ...

    public function warmUp(string $cacheDir): array
    {
        // ...

        return [
            SomeClassToPreload::class,
            AnotherClassClassToPreload::class,
            $cacheDir.'/some-file-to-preload.php',
            // ...
        ];
    }

    // ...
}
```

Commits
-------

649e530356 [HttpKernel] make kernels implementing `WarmableInterface` be part of the cache warmup stage

src/Symfony/Component/HttpKernel/CHANGELOG.md

@@ -6,6 +6,7 @@ CHANGELOG
 
  * made `WarmableInterface::warmUp()` return a list of classes or files to preload on PHP 7.4+;
    not returning an array is deprecated
+ * made kernels implementing `WarmableInterface` be part of the cache warmup stage
  * deprecated support for `service:action` syntax to reference controllers, use `serviceOrFqcn::method` instead
  * allowed using public aliases to reference controllers
  * added session usage reporting when the `_stateless` attribute of the request is set to `true`

src/Symfony/Component/HttpKernel/Kernel.php

@@ -35,6 +35,7 @@ use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\Bundle\BundleInterface;
+use Symfony\Component\HttpKernel\CacheWarmer\WarmableInterface;
 use Symfony\Component\HttpKernel\Config\FileLocator;
 use Symfony\Component\HttpKernel\DependencyInjection\AddAnnotatedClassesToCachePass;
 use Symfony\Component\HttpKernel\DependencyInjection\MergeExtensionConfigurationPass;
@@ -566,12 +567,14 @@ abstract class Kernel implements KernelInterface, RebootableInterface, Terminabl
             touch($oldContainerDir.'.legacy');
         }
 
-        if ($this->container->has('cache_warmer')) {
-            $preload = (array) $this->container->get('cache_warmer')->warmUp($this->container->getParameter('kernel.cache_dir'));
+        $preload = $this instanceof WarmableInterface ? (array) $this->warmUp($this->container->getParameter('kernel.cache_dir')) : [];
 
-            if ($preload && method_exists(Preloader::class, 'append') && file_exists($preloadFile = $cacheDir.'/'.$class.'.preload.php')) {
-                Preloader::append($preloadFile, $preload);
-            }
+        if ($this->container->has('cache_warmer')) {
+            $preload = array_merge($preload, (array) $this->container->get('cache_warmer')->warmUp($this->container->getParameter('kernel.cache_dir')));
+        }
+
+        if ($preload && method_exists(Preloader::class, 'append') && file_exists($preloadFile = $cacheDir.'/'.$class.'.preload.php')) {
+            Preloader::append($preloadFile, $preload);
         }
     }
 

src/Symfony/Component/HttpKernel/Tests/KernelTest.php

@@ -19,6 +19,7 @@ use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\Bundle\BundleInterface;
+use Symfony\Component\HttpKernel\CacheWarmer\WarmableInterface;
 use Symfony\Component\HttpKernel\DependencyInjection\ResettableServicePass;
 use Symfony\Component\HttpKernel\DependencyInjection\ServicesResetter;
 use Symfony\Component\HttpKernel\HttpKernelInterface;
@@ -480,6 +481,14 @@ EOF;
         $this->assertTrue($kernel->getContainer()->getParameter('test.processed'));
     }
 
+    public function testWarmup()
+    {
+        $kernel = new CustomProjectDirKernel();
+        $kernel->boot();
+
+        $this->assertTrue($kernel->warmedUp);
+    }
+
     public function testServicesResetter()
     {
         $httpKernelMock = $this->getMockBuilder(HttpKernelInterface::class)
@@ -603,8 +612,9 @@ class TestKernel implements HttpKernelInterface
     }
 }
 
-class CustomProjectDirKernel extends Kernel
+class CustomProjectDirKernel extends Kernel implements WarmableInterface
 {
+    public $warmedUp = false;
     private $baseDir;
     private $buildContainer;
     private $httpKernel;
@@ -631,6 +641,13 @@ class CustomProjectDirKernel extends Kernel
         return __DIR__.'/Fixtures';
     }
 
+    public function warmUp(string $cacheDir): array
+    {
+        $this->warmedUp = true;
+
+        return [];
+    }
+
     protected function build(ContainerBuilder $container)
     {
         if ($build = $this->buildContainer) {