[react-packager] Cache BundlesLayout

packager/react-packager/src/lib/loadCacheSync.js

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+const fs = require('fs');
+
+function loadCacheSync(cachePath) {
+  if (!fs.existsSync(cachePath)) {
+    return Object.create(null);
+  }
+
+  try {
+    return JSON.parse(fs.readFileSync(cachePath));
+  } catch (e) {
+    if (e instanceof SyntaxError) {
+      console.warn('Unable to parse cache file. Will clear and continue.');
+      fs.unlinkSync(cachePath);
+      return Object.create(null);
+    }
+    throw e;
+  }
+}
+
+module.exports = loadCacheSync;