Allow callback functions for creating jobs

$wgJobClasses can now specify a factory function for creating a job,
instead of a class to be instantiated directly. This makes it possible
to inject services in a job constructor, and register a factory function
that calls the constructor with default services.

This follows Ieb85493a7765 and Ia2107dc5af78, which introduced factory
functions for API modules and special pages.

Change-Id: I0461e59da2a8fa6681e3b1fcdfc38bfed7f3ac32

1 files changed, 15 insertions, 5 deletions

diff --git a/includes/jobqueue/Job.php b/includes/jobqueue/Job.php
index f814ceeb1b8b..703e48564bde 100644
--- a/includes/jobqueue/Job.php
+++ b/includes/jobqueue/Job.php
@@ -69,12 +69,22 @@ abstract class Job implements IJobSpecification {
 		global $wgJobClasses;
 
 		if ( isset( $wgJobClasses[$command] ) ) {
-			$class = $wgJobClasses[$command];
-
-			$job = new $class( $title, $params );
-			$job->command = $command;
+			$handler = $wgJobClasses[$command];
+
+			if ( is_callable( $handler ) ) {
+				$job = call_user_func( $handler, $title, $params );
+			} elseif ( class_exists( $handler ) ) {
+				$job = new $handler( $title, $params );
+			} else {
+				$job = null;
+			}
 
-			return $job;
+			if ( $job instanceof Job ) {
+				$job->command = $command;
+				return $job;
+			} else {
+				throw new InvalidArgumentException( "Cannot instantiate job '$command': bad spec!" );
+			}
 		}
 
 		throw new InvalidArgumentException( "Invalid job command '{$command}'" );