named_caches: make more resilient to corrupted state

client/tests/named_cache_test.py

 #!/usr/bin/env python
 # Copyright 2016 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 import logging
 import os
 import sys
 import tempfile
 import unittest
 
 ROOT_DIR = os.path.dirname(os.path.dirname(os.path.abspath(
     __file__.decode(sys.getfilesystemencoding()))))
 sys.path.insert(0, ROOT_DIR)
 sys.path.insert(0, os.path.join(ROOT_DIR, 'third_party'))
 
 from depot_tools import fix_encoding
 from utils import file_path
+from utils import fs
 import named_cache
 
 
 class CacheManagerTest(unittest.TestCase):
   def setUp(self):
     self.tempdir = tempfile.mkdtemp(prefix=u'named_cache_test')
     self.manager = named_cache.CacheManager(self.tempdir)
 
   def tearDown(self):
     try:
@@ skipping 56 matching lines @@
       for i in xrange(item_count):
         self.manager.request(str(i))
       self.assertEqual(len(self.manager), item_count)
       self.manager.trim(None)
       self.assertEqual(len(self.manager), named_cache.MAX_CACHE_SIZE)
       self.assertEqual(
           set(map(str, xrange(10, 10 + named_cache.MAX_CACHE_SIZE))),
           set(os.listdir(os.path.join(self.tempdir, 'named'))),
       )
 
+  def test_corrupted(self):
+    with open(os.path.join(self.tempdir, u'state.json'), 'w') as f:
+      f.write('}}}}')
+    fs.makedirs(os.path.join(self.tempdir, 'a'), 0777)
+    with self.manager.open():
+      self.assertFalse(os.path.isdir(self.tempdir))
+      self.manager.request('a')
+    self.assertTrue(fs.islink(os.path.join(self.tempdir, 'named', 'a')))
+
 
 if __name__ == '__main__':
   fix_encoding.fix_encoding()
   VERBOSE = '-v' in sys.argv
   logging.basicConfig(level=logging.DEBUG if VERBOSE else logging.ERROR)
   unittest.main()