Introduce service extensions by type (#44)

* Introduce extensions by type ExtendingModules can now declare extensions not only by specific ID but also by type. Services' extension handling has been moved to a separate class (`Container\ServiceExtensions`) to facilitate and decouple the handling of the new, more advanced behavior. * Implement ServiceExtensions with backward compatibility * Fix PHP 7.2/7.3 compatibilit in tests * Update docs ---- Signed-off-by: Giuseppe Mazzapica <[email protected]> Co-authored-by: Christian Leucht <[email protected]> Co-authored-by: Thorsten Frommen <[email protected]>
inpsyde · May 10, 2024 · feaa4d0 · feaa4d0
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diff --git a/docs/Modules.md b/docs/Modules.md
@@ -101,6 +101,125 @@ class ModuleWhichProvidesExtensions implements ExtendingModule
 }
 ```
 
+### Extending by type
+
+Sometimes it is desirable to extend a service by its type. Extending modules can do that as well:
+
+```php
+use Inpsyde\Modularity\Module\ExtendingModule;
+use Psr\Log\{LoggerInterface, LoggerAwareInterface};
+
+class LoggerAwareExtensionModule implements ExtendingModule
+{
+    public function extensions() : array 
+    {
+        return [
+            '@instanceof<Psr\Log\LoggerAwareInterface>' => static function(
+                LoggerAwareInterface $service,
+                ContainerInterface $c
+            ): ExtendedService {
+
+                if ($c->has(LoggerInterface::class)) {
+                    $service->setLogger($c->get(LoggerInterface::class));
+                }
+                return $service;
+            }
+        ];
+    }
+}
+```
+
+#### Types and subtypes
+
+The `@instanceof<T>` syntax works with class and interface names, targeting the given type and any 
+of its subtypes.
+
+For example, assuming the following objects:
+
+```php
+interface Animal {}
+class Dog implements Animal {}
+class BullDog extends Dog {}
+```
+
+and the following module: 
+
+```php
+class AnimalsExtensionModule implements ExtendingModule
+{
+    public function extensions() : array 
+    {
+        return [
+            '@instanceof<Animal>' => fn(Animal $animal) => $animal,
+            '@instanceof<Dog>' => fn(Dog $dog) => $dog,
+            '@instanceof<BullDog>' => fn(BullDog $bullDog) => $bullDog,
+        ];
+    }
+}
+```
+
+A service of type `BullDog` would go through all the 3 extensions.
+
+Note how extending callbacks can always safely declare the parameter type using in the signature
+the type they have in `@instanceof<T>`.
+
+#### Precedence
+
+The precedence of extensions-by-type resolution goes as follows:
+
+1. Extensions added to exact class
+2. Extensions added to any parent class
+3. Extensions added to any implemented interface
+
+Inside each of the three "groups", extensions are processed in _FIFO_ mode: the first added are the
+first processed.
+
+#### Name helper
+
+The syntax `"@instanceof<T>"` is an hardcoded string that might be error prone to type.
+
+The method `use Inpsyde\Modularity\Container\ServiceExtensions::typeId()` might be used to avoid 
+using hardcode strings. For example:
+
+```php
+use npsyde\Modularity\Container\ServiceExtensions;
+
+class AnimalsExtensionModule implements ExtendingModule
+{
+    public function extensions() : array 
+    {
+        return [
+            ServiceExtensions::typeId(Animal::class) => fn(Animal $animal) => $animal,
+            ServiceExtensions::typeId(Dog::class) => fn(Dog $dog) => $dog,
+            ServiceExtensions::typeId(BullDog::class) => fn(BullDog $bullDog) => $bullDog,
+        ];
+    }
+}
+```
+
+#### Only for objects
+
+Extensions-by-type only work for objects. Any usage of `@instanceof<T>` syntax with a string that is
+a class/interface name will be ignored.
+That means it is not possible to extend by type scalar/array services nor pseudo-types like 
+`iterable` or `callable`.
+
+#### Possibly recursive
+
+Extensions by type might be recursive. For example, an extension for type `A` that returns an 
+instance of `B` will prevent further extensions to type `A` to execute (unless `B` is a child of `A`)
+and will trigger execution of extensions for type `B`.
+**Infinite recursion is prevented**. So if extensions for `A` return `B` and extensions for `B`
+return `A` that's where it stops, returning an `A` instance.
+
+#### Use carefully
+
+**Please note**: extensions-by-type have a performance impact especially when type extensions are 
+used to return a different type, because of possible recursions.
+As a reference, it was measured that resolving 10000 objects in the container, each having 9 
+extensions-by-type callbacks, on a very fast server, on PHP 8, for one concurrent user, takes 
+between 80 and 90 milliseconds.
+
 ## ExecutableModule
 If there is functionality that needs to be executed, you can make the Module executable like following:
 

diff --git a/src/Container/ContainerConfigurator.php b/src/Container/ContainerConfigurator.php
@@ -19,9 +19,9 @@ class ContainerConfigurator
     private $factoryIds = [];
 
     /**
-     * @var array<string, array<callable(mixed $service, ContainerInterface $container):mixed>>
+     * @var ServiceExtensions
      */
-    private $extensions = [];
+    private $extensions;
 
     /**
      * @var ContainerInterface[]
@@ -38,9 +38,10 @@ class ContainerConfigurator
      *
      * @param ContainerInterface[] $containers
      */
-    public function __construct(array $containers = [])
+    public function __construct(array $containers = [], ?ServiceExtensions $extensions = null)
     {
         array_map([$this, 'addContainer'], $containers);
+        $this->extensions = $extensions ?? new ServiceExtensions();
     }
 
     /**
@@ -115,11 +116,7 @@ public function hasService(string $id): bool
      */
     public function addExtension(string $id, callable $extender): void
     {
-        if (!isset($this->extensions[$id])) {
-            $this->extensions[$id] = [];
-        }
-
-        $this->extensions[$id][] = $extender;
+        $this->extensions->add($id, $extender);
     }
 
     /**
@@ -129,7 +126,7 @@ public function addExtension(string $id, callable $extender): void
      */
     public function hasExtension(string $id): bool
     {
-        return isset($this->extensions[$id]);
+        return $this->extensions->has($id);
     }
 
     /**

diff --git a/src/Container/ReadOnlyContainer.php b/src/Container/ReadOnlyContainer.php
@@ -20,7 +20,7 @@ class ReadOnlyContainer implements ContainerInterface
     private $factoryIds;
 
     /**
-     * @var array<string, array<callable(mixed, ContainerInterface $container):mixed>>
+     * @var ServiceExtensions
      */
     private $extensions;
 
@@ -41,18 +41,18 @@ class ReadOnlyContainer implements ContainerInterface
      *
      * @param array<string, callable(ContainerInterface $container):mixed> $services
      * @param array<string, bool> $factoryIds
-     * @param array<string, array<callable(mixed, ContainerInterface $container):mixed>> $extensions
+     * @param ServiceExtensions|array $extensions
      * @param ContainerInterface[] $containers
      */
     public function __construct(
         array $services,
         array $factoryIds,
-        array $extensions,
+        $extensions,
         array $containers
     ) {
         $this->services = $services;
         $this->factoryIds = $factoryIds;
-        $this->extensions = $extensions;
+        $this->extensions = $this->configureServiceExtensions($extensions);
         $this->containers = $containers;
     }
 
@@ -69,7 +69,7 @@ public function get(string $id)
 
         if (array_key_exists($id, $this->services)) {
             $service = $this->services[$id]($this);
-            $resolved = $this->resolveExtensions($id, $service);
+            $resolved = $this->extensions->resolve($service, $id, $this);
 
             if (!isset($this->factoryIds[$id])) {
                 $this->resolvedServices[$id] = $resolved;
@@ -83,7 +83,7 @@ public function get(string $id)
             if ($container->has($id)) {
                 $service = $container->get($id);
 
-                return $this->resolveExtensions($id, $service);
+                return $this->extensions->resolve($service, $id, $this);
             }
         }
 
@@ -118,21 +118,42 @@ public function has(string $id): bool
     }
 
     /**
-     * @param string $id
-     * @param mixed $service
+     * Support extensions as array or ServiceExtensions instance for backward compatibility.
      *
-     * @return mixed
+     * With PHP 8+ we could use an actual union type, but when we bump to PHP 8 as min supported
+     * version, we will probably bump major version as well, so we can just get rid of support
+     * for array.
+     *
+     * @param mixed $extensions
+     * @return ServiceExtensions
      */
-    private function resolveExtensions(string $id, $service)
+    private function configureServiceExtensions($extensions): ServiceExtensions
     {
-        if (!isset($this->extensions[$id])) {
-            return $service;
+        if ($extensions instanceof ServiceExtensions) {
+            return $extensions;
+        }
+
+        if (!is_array($extensions)) {
+            throw new \TypeError(
+                sprintf(
+                    '%s::%s(): Argument #3 ($extensions) must be of type %s|array, %s given',
+                    __CLASS__,
+                    '__construct',
+                    ServiceExtensions::class,
+                    gettype($extensions)
+                )
+            );
         }
 
-        foreach ($this->extensions[$id] as $extender) {
-            $service = $extender($service, $this);
+        $servicesExtensions = new ServiceExtensions();
+        foreach ($extensions as $id => $callback) {
+            /**
+             * @var string $id
+             * @var callable(mixed,ContainerInterface):mixed $callback
+             */
+            $servicesExtensions->add($id, $callback);
         }
 
-        return $service;
+        return $servicesExtensions;
     }
 }