Fix require reverting changes even though dependency resolution succeeded if when something fails afterwards, closes #10118

src/Composer/Command/RequireCommand.php

@@ -20,6 +20,7 @@ use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
 use Composer\Factory;
 use Composer\Installer;
+use Composer\Installer\InstallerEvents;
 use Composer\Json\JsonFile;
 use Composer\Json\JsonManipulator;
 use Composer\Package\Version\VersionParser;
@@ -52,6 +53,8 @@ class RequireCommand extends InitCommand
     private $lock;
     /** @var ?string contents before modification if the lock file exists */
     private $lockBackup;
+    /** @var bool */
+    private $dependencyResolutionCompleted = false;
 
     protected function configure()
     {
@@ -270,7 +273,9 @@ EOT
         try {
             return $this->doUpdate($input, $output, $io, $requirements, $requireKey, $removeKey);
         } catch (\Exception $e) {
-            $this->revertComposerFile(false);
+            if (!$this->dependencyResolutionCompleted) {
+                $this->revertComposerFile(false);
+            }
             throw $e;
         }
     }
@@ -311,6 +316,14 @@ EOT
         );
     }
 
+    /**
+     * @private
+     */
+    public function markSolverComplete()
+    {
+        $this->dependencyResolutionCompleted = true;
+    }
+
     private function doUpdate(InputInterface $input, OutputInterface $output, IOInterface $io, array $requirements, $requireKey, $removeKey)
     {
         // Update packages
@@ -318,6 +331,9 @@ EOT
         $composer = $this->getComposer(true, $input->getOption('no-plugins'));
         $composer->getEventDispatcher()->setRunScripts(!$input->getOption('no-scripts'));
 
+        $this->dependencyResolutionCompleted = false;
+        $composer->getEventDispatcher()->addListener(InstallerEvents::PRE_OPERATIONS_EXEC, [$this, 'markSolverComplete'], 10000);
+
         if ($input->getOption('dry-run')) {
             $rootPackage = $composer->getPackage();
             $links = array(