Issue #3382942: Eliminate dependencies on Composer Stager internals

package_manager/src/StageBase.php

@@ -323,14 +323,13 @@ abstract class StageBase implements LoggerAwareInterface {
     $active_dir = $this->pathFactory->create($this->pathLocator->getProjectRoot());
     $stage_dir = $this->pathFactory->create($this->getStageDirectory());
 
-    $excluded_paths = $this->getPathsToExclude();
-    $event = new PreCreateEvent($this, $excluded_paths);
+    $event = new PreCreateEvent($this, $this->getPathsToExclude());
     // If an error occurs and we won't be able to create the stage, mark it as
     // available.
     $this->dispatch($event, [$this, 'markAsAvailable']);
 
     try {
-      $this->beginner->begin($active_dir, $stage_dir, $excluded_paths, NULL, $timeout);
+      $this->beginner->begin($active_dir, $stage_dir, $event->excludedPaths, NULL, $timeout);
     }
     catch (\Throwable $error) {
       $this->destroy();
@@ -442,24 +441,22 @@ abstract class StageBase implements LoggerAwareInterface {
     $active_dir = $this->pathFactory->create($this->pathLocator->getProjectRoot());
     $stage_dir = $this->pathFactory->create($this->getStageDirectory());
 
-    $excluded_paths = $this->getPathsToExclude();
-    // Exclude the failure file from the commit operation.
-    $excluded_paths->add(
-      str_replace($active_dir->absolute() . DIRECTORY_SEPARATOR, '', $this->failureMarker->getPath()),
-    );
-
     // If an error occurs while dispatching the events, ensure that ::destroy()
     // doesn't think we're in the middle of applying the staged changes to the
     // active directory.
-    $event = new PreApplyEvent($this, $excluded_paths);
+    $event = new PreApplyEvent($this, $this->getPathsToExclude());
     $this->tempStore->set(self::TEMPSTORE_APPLY_TIME_KEY, $this->time->getRequestTime());
     $this->dispatch($event, $this->setNotApplying(...));
 
+    // Exclude the failure file from the commit operation.
+    $event->excludedPaths->add(
+      str_replace($active_dir->absolute() . DIRECTORY_SEPARATOR, '', $this->failureMarker->getPath()),
+    );
     // Create a marker file so that we can tell later on if the commit failed.
     $this->failureMarker->write($this, $this->getFailureMarkerMessage());
 
     try {
-      $this->committer->commit($stage_dir, $active_dir, $excluded_paths, NULL, $timeout);
+      $this->committer->commit($stage_dir, $active_dir, $event->excludedPaths, NULL, $timeout);
     }
     catch (InvalidArgumentException | PreconditionException $e) {
       // The commit operation has not started yet, so we can clear the failure