Add a readonly mode to the cache, fixes #9150

doc/06-config.md

@@ -204,6 +204,10 @@ downloads. When the garbage collection is periodically ran, this is the maximum
 size the cache will be able to use. Older (less used) files will be removed
 first until the cache fits.
 
+## cache-read-only
+
+Defaults to `false`. Whether to use the Composer cache in read-only mode.
+
 ## bin-compat
 
 Defaults to `auto`. Determines the compatibility of the binaries to be installed.

res/composer-schema.json

@@ -237,6 +237,10 @@
                     "type": ["string", "integer"],
                     "description": "The cache max size for the files cache, defaults to \"300MiB\"."
                 },
+                "cache-read-only": {
+                    "type": ["boolean"],
+                    "description": "Whether to use the Composer cache in read-only mode."
+                },
                 "bin-compat": {
                     "enum": ["auto", "full"],
                     "description": "The compatibility of the binaries, defaults to \"auto\" (automatically guessed) and can be \"full\" (compatible with both Windows and Unix-based systems)."

src/Composer/Cache.php

@@ -30,19 +30,22 @@ class Cache
     private $enabled = true;
     private $allowlist;
     private $filesystem;
+    private $readOnly;
 
     /**
      * @param IOInterface $io
      * @param string      $cacheDir   location of the cache
      * @param string      $allowlist  List of characters that are allowed in path names (used in a regex character class)
      * @param Filesystem  $filesystem optional filesystem instance
+     * @param bool        $readOnly   whether the cache is in readOnly mode
      */
-    public function __construct(IOInterface $io, $cacheDir, $allowlist = 'a-z0-9.', Filesystem $filesystem = null)
+    public function __construct(IOInterface $io, $cacheDir, $allowlist = 'a-z0-9.', Filesystem $filesystem = null, $readOnly = false)
     {
         $this->io = $io;
         $this->root = rtrim($cacheDir, '/\\') . '/';
         $this->allowlist = $allowlist;
         $this->filesystem = $filesystem ?: new Filesystem();
+        $this->readOnly = (bool) $readOnly;
 
         if (!self::isUsable($cacheDir)) {
             $this->enabled = false;
@@ -59,6 +62,22 @@ class Cache
         }
     }
 
+    /**
+     * @param bool $readOnly
+     */
+    public function setReadOnly($readOnly)
+    {
+        $this->readOnly = (bool) $readOnly;
+    }
+
+    /**
+     * @return bool
+     */
+    public function isReadOnly()
+    {
+        return $this->readOnly;
+    }
+
     public static function isUsable($path)
     {
         return !preg_match('{(^|[\\\\/])(\$null|nul|NUL|/dev/null)([\\\\/]|$)}', $path);
@@ -90,7 +109,7 @@ class Cache
 
     public function write($file, $contents)
     {
-        if ($this->enabled) {
+        if ($this->enabled && !$this->readOnly) {
             $file = preg_replace('{[^'.$this->allowlist.']}i', '-', $file);
 
             $this->io->writeError('Writing '.$this->root . $file.' into cache', true, IOInterface::DEBUG);
@@ -128,7 +147,7 @@ class Cache
      */
     public function copyFrom($file, $source)
     {
-        if ($this->enabled) {
+        if ($this->enabled && !$this->readOnly) {
             $file = preg_replace('{[^'.$this->allowlist.']}i', '-', $file);
             $this->filesystem->ensureDirectoryExists(dirname($this->root . $file));
 

src/Composer/Command/ClearCacheCommand.php

@@ -59,6 +59,7 @@ EOT
                 continue;
             }
             $cache = new Cache($io, $cachePath);
+            $cache->setReadOnly($config->get('cache-read-only'));
             if (!$cache->isEnabled()) {
                 $io->writeError("<info>Cache is not enabled ($key): $cachePath</info>");
 

src/Composer/Config.php

@@ -41,6 +41,7 @@ class Config
         'cache-ttl' => 15552000, // 6 months
         'cache-files-ttl' => null, // fallback to cache-ttl
         'cache-files-maxsize' => '300MiB',
+        'cache-read-only' => false,
         'bin-compat' => 'auto',
         'discard-changes' => false,
         'autoloader-suffix' => null,
@@ -236,6 +237,7 @@ class Config
                 return (($flags & self::RELATIVE_PATHS) == self::RELATIVE_PATHS) ? $val : $this->realpath($val);
 
             // booleans with env var support
+            case 'cache-read-only':
             case 'htaccess-protect':
                 // convert foo-bar to COMPOSER_FOO_BAR and check if it exists since it overrides the local config
                 $env = 'COMPOSER_' . strtoupper(strtr($key, '-', '_'));

src/Composer/Downloader/FileDownloader.php

@@ -187,7 +187,7 @@ class FileDownloader implements DownloaderInterface, ChangeReportInterface
             $url = reset($urls);
             $cacheKey = $url['cacheKey'];
 
-            if ($cache) {
+            if ($cache && !$cache->isReadOnly()) {
                 $self->lastCacheWrites[$package->getName()] = $cacheKey;
                 $cache->copyFrom($cacheKey, $fileName);
             }

src/Composer/Factory.php

@@ -477,6 +477,7 @@ class Factory
         $cache = null;
         if ($config->get('cache-files-ttl') > 0) {
             $cache = new Cache($io, $config->get('cache-files-dir'), 'a-z0-9_./');
+            $cache->setReadOnly($config->get('cache-read-only'));
         }
 
         $fs = new Filesystem($process);

src/Composer/Repository/ComposerRepository.php

@@ -130,6 +130,7 @@ class ComposerRepository extends ArrayRepository implements ConfigurableReposito
         $this->baseUrl = rtrim(preg_replace('{(?:/[^/\\\\]+\.json)?(?:[?#].*)?$}', '', $this->url), '/');
         $this->io = $io;
         $this->cache = new Cache($io, $config->get('cache-repo-dir').'/'.preg_replace('{[^a-z0-9.]}i', '-', $this->url), 'a-z0-9.$~');
+        $this->cache->setReadOnly($config->get('cache-read-only'));
         $this->versionParser = new VersionParser();
         $this->loader = new ArrayLoader($this->versionParser);
         $this->httpDownloader = $httpDownloader;
@@ -1071,7 +1072,7 @@ class ComposerRepository extends ArrayRepository implements ConfigurableReposito
                 $data = $response->decodeJson();
                 HttpDownloader::outputWarnings($this->io, $this->url, $data);
 
-                if ($cacheKey) {
+                if ($cacheKey && !$this->cache->isReadOnly()) {
                     if ($storeLastModifiedTime) {
                         $lastModifiedDate = $response->getHeader('last-modified');
                         if ($lastModifiedDate) {
@@ -1155,7 +1156,9 @@ class ComposerRepository extends ArrayRepository implements ConfigurableReposito
                     $data['last-modified'] = $lastModifiedDate;
                     $json = json_encode($data);
                 }
-                $this->cache->write($cacheKey, $json);
+                if (!$this->cache->isReadOnly()) {
+                    $this->cache->write($cacheKey, $json);
+                }
 
                 return $data;
             } catch (\Exception $e) {
@@ -1238,7 +1241,9 @@ class ComposerRepository extends ArrayRepository implements ConfigurableReposito
                 $data['last-modified'] = $lastModifiedDate;
                 $json = JsonFile::encode($data, JsonFile::JSON_UNESCAPED_SLASHES | JsonFile::JSON_UNESCAPED_UNICODE);
             }
-            $cache->write($cacheKey, $json);
+            if (!$cache->isReadOnly()) {
+                $cache->write($cacheKey, $json);
+            }
             $repo->freshMetadataUrls[$filename] = true;
 
             return $data;

src/Composer/Repository/Vcs/BitbucketDriver.php

@@ -60,6 +60,7 @@ abstract class BitbucketDriver extends VcsDriver
                 $this->repository,
             ))
         );
+        $this->cache->setReadOnly($this->config->get('cache-read-only'));
     }
 
     /**

src/Composer/Repository/Vcs/GitDriver.php

@@ -75,6 +75,7 @@ class GitDriver extends VcsDriver
         $this->getBranches();
 
         $this->cache = new Cache($this->io, $this->config->get('cache-repo-dir').'/'.preg_replace('{[^a-z0-9.]}i', '-', $cacheUrl));
+        $this->cache->setReadOnly($this->config->get('cache-read-only'));
     }
 
     /**

src/Composer/Repository/Vcs/GitHubDriver.php

@@ -58,6 +58,7 @@ class GitHubDriver extends VcsDriver
             $this->originUrl = 'github.com';
         }
         $this->cache = new Cache($this->io, $this->config->get('cache-repo-dir').'/'.$this->originUrl.'/'.$this->owner.'/'.$this->repository);
+        $this->cache->setReadOnly($this->config->get('cache-read-only'));
 
         if ( $this->config->get('use-github-api') === false || (isset($this->repoConfig['no-api']) && $this->repoConfig['no-api'] ) ){
             $this->setupGitDriver($this->url);

src/Composer/Repository/Vcs/GitLabDriver.php

@@ -105,6 +105,7 @@ class GitLabDriver extends VcsDriver
         $this->repository = preg_replace('#(\.git)$#', '', $match['repo']);
 
         $this->cache = new Cache($this->io, $this->config->get('cache-repo-dir').'/'.$this->originUrl.'/'.$this->namespace.'/'.$this->repository);
+        $this->cache->setReadOnly($this->config->get('cache-read-only'));
 
         $this->fetchProject();
     }

src/Composer/Repository/Vcs/SvnDriver.php

@@ -78,6 +78,7 @@ class SvnDriver extends VcsDriver
         }
 
         $this->cache = new Cache($this->io, $this->config->get('cache-repo-dir').'/'.preg_replace('{[^a-z0-9.]}i', '-', $this->baseUrl));
+        $this->cache->setReadOnly($this->config->get('cache-read-only'));
 
         $this->getBranches();
         $this->getTags();