Change the file download cache key with the processed URL, implement custom cache key

src/Composer/Downloader/FileDownloader.php

@@ -113,6 +113,10 @@ class FileDownloader implements DownloaderInterface, ChangeReportInterface
             $urls[$index] = array(
                 'base' => $url,
                 'processed' => $processedUrl,
+                // we use the complete download url here to avoid conflicting entries
+                // 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, $processedUrl)
             );
         }
@@ -136,6 +140,11 @@ class FileDownloader implements DownloaderInterface, ChangeReportInterface
             if ($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, $preFileDownloadEvent->getCustomCacheKey());
+                } else if ($preFileDownloadEvent->getProcessedUrl() !== $url['processed']) {
+                    $url['cacheKey'] = $this->getCacheKey($package, $preFileDownloadEvent->getProcessedUrl());
+                }
                 $url['processed'] = $preFileDownloadEvent->getProcessedUrl();
             }
 
@@ -398,14 +407,9 @@ class FileDownloader implements DownloaderInterface, ChangeReportInterface
         return $url;
     }
 
-    private function getCacheKey(PackageInterface $package, $processedUrl)
+    private function getCacheKey(PackageInterface $package, $key)
     {
-        // we use the complete download url here to avoid conflicting entries
-        // 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.
-        $cacheKey = sha1($processedUrl);
-
+        $cacheKey = sha1($key);
         return $package->getName().'/'.$cacheKey.'.'.$package->getDistType();
     }
 

src/Composer/Plugin/PreFileDownloadEvent.php

@@ -32,6 +32,11 @@ class PreFileDownloadEvent extends Event
      */
     private $processedUrl;
 
+    /**
+     * @var string
+     */
+    private $customCacheKey;
+
     /**
      * @var string
      */
@@ -88,6 +93,26 @@ class PreFileDownloadEvent extends Event
         $this->processedUrl = $processedUrl;
     }
 
+    /**
+     * Retrieves a custom package cache key for this download.
+     *
+     * @return string
+     */
+    public function getCustomCacheKey()
+    {
+        return $this->customCacheKey;
+    }
+
+    /**
+     * Sets a custom package cache key for this download.
+     *
+     * @param string $customCacheKey New cache key
+     */
+    public function setCustomCacheKey($customCacheKey)
+    {
+        $this->customCacheKey = $customCacheKey;
+    }
+
     /**
      * Returns the type of this download (package, metadata).
      *