Callable parameter injection

This is like what we have to DI and classes, but for callables.

The motivating factor is to get rid of *service locators* in the `boot`
method of apps as a new pattern is about to emerge where we have lots of
`query` calls on the app or server container in order to fetch some
services.

With this little helper it's possible to call another (public) method
and magically have everything injected.

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

1 files changed, 22 insertions, 0 deletions

diff --git a/lib/public/AppFramework/Bootstrap/IBootContext.php b/lib/public/AppFramework/Bootstrap/IBootContext.php
index 6ceec5d2fcb..47b26528c66 100644
--- a/lib/public/AppFramework/Bootstrap/IBootContext.php
+++ b/lib/public/AppFramework/Bootstrap/IBootContext.php
@@ -26,7 +26,9 @@ declare(strict_types=1);
 namespace OCP\AppFramework\Bootstrap;
 
 use OCP\AppFramework\IAppContainer;
+use OCP\AppFramework\QueryException;
 use OCP\IServerContainer;
+use Throwable;
 
 /**
  * @since 20.0.0
@@ -52,4 +54,24 @@ interface IBootContext {
 	 * @since 20.0.0
 	 */
 	public function getServerContainer(): IServerContainer;
+
+	/**
+	 * Invoke the given callable and inject all parameters based on their types
+	 * and names
+	 *
+	 * Note: when used with methods, make sure they are public or use \Closure::fromCallable
+	 * to wrap the private method call, e.g.
+	 *  * `$context->injectFn([$obj, 'publicMethod'])`
+	 *  * `$context->injectFn([$this, 'publicMethod'])`
+	 *  * `$context->injectFn(\Closure::fromCallable([$this, 'privateMethod']))`
+	 *
+	 * Note: the app container will be queried
+	 *
+	 * @param callable $fn
+	 * @throws QueryException if at least one of the parameter can't be resolved
+	 * @throws Throwable any error the function invocation might cause
+	 * @return mixed|null the return value of the invoked function, if any
+	 * @since 20.0.0
+	 */
+	public function injectFn(callable $fn);
 }