From 78d7792eb810319f86421071bf795ce41eca24f2 Mon Sep 17 00:00:00 2001
From: Jordi Boggiano <j.boggiano@seld.be>
Date: Wed, 10 Feb 2021 10:03:44 +0100
Subject: [PATCH] Fix handling of promises for uninstall step when updating to
 a different install source

---
 src/Composer/Installer/InstallationManager.php | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/Composer/Installer/InstallationManager.php b/src/Composer/Installer/InstallationManager.php
index f8a0e5708..01148583a 100644
--- a/src/Composer/Installer/InstallationManager.php
+++ b/src/Composer/Installer/InstallationManager.php
@@ -492,9 +492,15 @@ class InstallationManager
             $promise = $installer->update($repo, $initial, $target);
             $this->markForNotification($target);
         } else {
-            $this->getInstaller($initialType)->uninstall($repo, $initial);
+            $promise = $this->getInstaller($initialType)->uninstall($repo, $initial);
+            if (!$promise instanceof PromiseInterface) {
+                $promise = \React\Promise\resolve();
+            }
+
             $installer = $this->getInstaller($targetType);
-            $promise = $installer->install($repo, $target);
+            $promise->then(function () use ($installer, $repo, $target) {
+                return $installer->install($repo, $target);
+            });
         }
 
         return $promise;