Fix using inside anonymous function

src/Composer/Downloader/FileDownloader.php

@@ -106,6 +106,11 @@ class FileDownloader implements DownloaderInterface, ChangeReportInterface
             throw new \InvalidArgumentException('The given package is missing url information');
         }
 
+        $generateCacheKey = function (PackageInterface $package, $key) {
+            $cacheKey = sha1($key);
+            return $package->getName().'/'.$cacheKey.'.'.$package->getDistType();
+        };
+
         $retries = 3;
         $urls = $package->getDistUrls();
         foreach ($urls as $index => $url) {
@@ -117,7 +122,7 @@ class FileDownloader implements DownloaderInterface, ChangeReportInterface
                 // from different packages, which would potentially allow a given package
                 // in a third party repo to pre-populate the cache for the same package in
                 // packagist for example.
-                'cacheKey' => $this->getCacheKey($package, $processedUrl)
+                'cacheKey' => $generateCacheKey($package, $processedUrl)
             );
         }
 
@@ -134,16 +139,16 @@ class FileDownloader implements DownloaderInterface, ChangeReportInterface
 
         $accept = null;
         $reject = null;
-        $download = function () use ($io, $output, $httpDownloader, $cache, $eventDispatcher, $package, $fileName, &$urls, &$accept, &$reject) {
+        $download = function () use ($io, $output, $httpDownloader, $cache, $generateCacheKey, $eventDispatcher, $package, $fileName, &$urls, &$accept, &$reject) {
             $url = reset($urls);
 
             if ($eventDispatcher) {
                 $preFileDownloadEvent = new PreFileDownloadEvent(PluginEvents::PRE_FILE_DOWNLOAD, $httpDownloader, $url['processed'], 'package', $package);
                 $eventDispatcher->dispatch($preFileDownloadEvent->getName(), $preFileDownloadEvent);
                 if ($preFileDownloadEvent->getCustomCacheKey() !== null) {
-                    $url['cacheKey'] = $this->getCacheKey($package, $preFileDownloadEvent->getCustomCacheKey());
+                    $url['cacheKey'] = $generateCacheKey($package, $preFileDownloadEvent->getCustomCacheKey());
                 } else if ($preFileDownloadEvent->getProcessedUrl() !== $url['processed']) {
-                    $url['cacheKey'] = $this->getCacheKey($package, $preFileDownloadEvent->getProcessedUrl());
+                    $url['cacheKey'] = $generateCacheKey($package, $preFileDownloadEvent->getProcessedUrl());
                 }
                 $url['processed'] = $preFileDownloadEvent->getProcessedUrl();
             }
@@ -407,12 +412,6 @@ class FileDownloader implements DownloaderInterface, ChangeReportInterface
         return $url;
     }
 
-    private function getCacheKey(PackageInterface $package, $key)
-    {
-        $cacheKey = sha1($key);
-        return $package->getName().'/'.$cacheKey.'.'.$package->getDistType();
-    }
-
     /**
      * {@inheritDoc}
      * @throws \RuntimeException