metro-bundler: recreate temp dir if does not exist

Summary: That happens after a reboot on macOS for example, because temp dir is wiped.

Reviewed By: davidaurelio

Differential Revision: D5236249

fbshipit-source-id: be19cd97a7488850e3195b3fc419779ed0df2c38

packages/metro-bundler/src/lib/TempDirs.js

@@ -25,7 +25,7 @@ class CannotCreateTempDirError extends Error {
  * Claim a temporary directory that doesn't exist already and that cannot be
  * predicted, so that nobody can race us to it. This is similar to `mkdtemp(3)`.
  */
-function create(pathPrefix: string): string {
+function create(pathPrefix: string, mode: number): string {
   let resultPath;
   let i = 0;
   do {
@@ -34,7 +34,7 @@ function create(pathPrefix: string): string {
     if (++i === 10) {
       throw new CannotCreateTempDirError();
     }
-  } while (!tryMkdirSync(resultPath));
+  } while (!tryMkdirSync(resultPath, mode));
   return resultPath;
 }
 

packages/metro-bundler/src/lib/TransformCaching.js

@@ -446,27 +446,57 @@ function useTempDir(): TransformCache {
  * clone gets a fresh cache, and so that the temp dir used cannot be predicted.
  * Sometimes a different user build the same project, in which case we use a
  * different subfolder of the temp directory.
+ *
+ * If the directory specified in the `.metro-bundler` doesn't exist anymore
+ * (ex. after a machine reboot and `/tmp` has been cleaned), we just create
+ * a new one.
  */
 function useProjectDir(projectPath: string): TransformCache {
-  const metaDirPath = readMetaDirPath(projectPath);
+  invariant(path.isAbsolute(projectPath), 'project path must be absolute');
+  const metaFilePath = path.resolve(projectPath, '.metro-bundler');
+  const metaDirPath = readMetaDirPath(metaFilePath);
+  if (metaDirPath != null) {
+    try {
+      return useMetaDirPath(metaDirPath);
+    } catch (error) {
+      if (error.code !== 'ENOENT') {
+        throw error;
+      }
+    }
+  }
+  return useMetaDirPath(createMetaDir(metaFilePath));
+}
+
+/**
+ * Use the specified path as cache, by creating a subdirectory specific to the
+ * current user ID. This could fail if `metaDirPath` doesn't exist.
+ */
+function useMetaDirPath(metaDirPath: string): TransformCache {
   const uidStr = process.getuid != null ? process.getuid().toString() : 'g';
   const finalPath = path.join(metaDirPath, '_' + uidStr);
-  TempDirs.tryMkdirSync(finalPath, 448 /* == 0700 */);
+  TempDirs.tryMkdirSync(finalPath, 0o700);
   return new FileBasedCache(finalPath);
 }
 
-function readMetaDirPath(projectPath: string): string {
-  invariant(path.isAbsolute(projectPath), 'project path must be absolute');
-  const metaFilePath = path.resolve(projectPath, '.metro-bundler');
+/**
+ * Return the path of the cache directory, if it's already been set for that
+ * project, in the shape of a `.metro-bundler` file.
+ */
+function readMetaDirPath(metaFilePath: string): ?string {
   const metaFile = tryReadFileSync(metaFilePath);
-  if (metaFile != null) {
-    const metaDirPath = metaFile.split('\n')[0];
-    if (metaDirPath != null) {
-      return metaDirPath;
-    }
+  if (metaFile == null) {
+    return null;
   }
+  return metaFile.split('\n')[0];
+}
+
+/**
+ * Create a new top-level directory to be used for the cache. We give all
+ * permissions because different users might share that directory.
+ */
+function createMetaDir(metaFilePath: string): string {
   const tmpDirPath = tmpdir();
-  const metaDirPath = TempDirs.create(path.join(tmpDirPath, 'mb-'));
+  const metaDirPath = TempDirs.create(path.join(tmpDirPath, 'mb-'), 0o777);
   fs.writeFileSync(metaFilePath, metaDirPath + '\n');
   return metaDirPath;
 }