Trim trailing slash in path downloader to avoid symlink issues, and in FileDownloader::getLocalChanges as we append a string without slash, refs #9422

src/Composer/Downloader/FileDownloader.php

@@ -429,6 +429,7 @@ class FileDownloader implements DownloaderInterface, ChangeReportInterface
         $e = null;
         $output = '';
 
+        $targetDir = Filesystem::trimTrailingSlash($targetDir);
         try {
             if (is_dir($targetDir.'_compare')) {
                 $this->filesystem->removeDirectory($targetDir.'_compare');

src/Composer/Downloader/PathDownloader.php

@@ -47,6 +47,7 @@ class PathDownloader extends FileDownloader implements VcsCapableDownloaderInter
      */
     public function download(PackageInterface $package, $path, PackageInterface $prevPackage = null, $output = true)
     {
+        $path = Filesystem::trimTrailingSlash($path);
         $url = $package->getDistUrl();
         $realUrl = realpath($url);
         if (false === $realUrl || !file_exists($realUrl) || !is_dir($realUrl)) {
@@ -80,6 +81,7 @@ class PathDownloader extends FileDownloader implements VcsCapableDownloaderInter
      */
     public function install(PackageInterface $package, $path, $output = true)
     {
+        $path = Filesystem::trimTrailingSlash($path);
         $url = $package->getDistUrl();
         $realUrl = realpath($url);
 
@@ -178,6 +180,7 @@ class PathDownloader extends FileDownloader implements VcsCapableDownloaderInter
      */
     public function remove(PackageInterface $package, $path, $output = true)
     {
+        $path = Filesystem::trimTrailingSlash($path);
         /**
          * realpath() may resolve Windows junctions to the source path, so we'll check for a junction first
          * to prevent a false positive when checking if the dist and install paths are the same.
@@ -209,6 +212,7 @@ class PathDownloader extends FileDownloader implements VcsCapableDownloaderInter
      */
     public function getVcsReference(PackageInterface $package, $path)
     {
+        $path = Filesystem::trimTrailingSlash($path);
         $parser = new VersionParser;
         $guesser = new VersionGuesser($this->config, $this->process, $parser);
         $dumper = new ArrayDumper;

src/Composer/Util/Filesystem.php

@@ -506,6 +506,23 @@ class Filesystem
         return $prefix.($absolute ? '/' : '').implode('/', $parts);
     }
 
+    /**
+     * Remove trailing slashes if present to avoid issues with symlinks
+     *
+     * And other possible unforeseen disasters, see https://github.com/composer/composer/pull/9422
+     *
+     * @param  string $path
+     * @return bool
+     */
+    public static function trimTrailingSlash($path)
+    {
+        if (!preg_match('{^[/\\\\]+$}', $path)) {
+            $path = rtrim($path, '/\\');
+        }
+
+        return $path;
+    }
+
     /**
      * Return if the given path is local
      *