Add unit test to clean_caches()

client/named_cache.py

 # 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.
 
 """This file implements Named Caches."""
 
 import contextlib
 import logging
 import optparse
 import os
@@ skipping 178 matching lines @@
 
   def trim(self, min_free_space):
     """Purges cache.
 
     Removes cache directories that were not accessed for a long time
     until there is enough free space and the number of caches is sane.
 
     If min_free_space is None, disk free space is not checked.
 
     Requires NamedCache to be open.
+
+    Returns:
+      Number of caches deleted.
     """
     self._lock.assert_locked()
     if not os.path.isdir(self.root_dir):
-      return
+      return 0
 
+    total = 0
     free_space = 0
     if min_free_space:
       free_space = file_path.get_free_space(self.root_dir)
     while ((min_free_space and free_space < min_free_space)
            or len(self._lru) > MAX_CACHE_SIZE):
       logging.info(
           'Making space for named cache %s > %s or %s > %s',
           free_space, min_free_space, len(self._lru), MAX_CACHE_SIZE)
       try:
         name, (path, _) = self._lru.get_oldest()
       except KeyError:
-        return
+        return total
       named_dir = self._get_named_path(name)
       if fs.islink(named_dir):
         fs.unlink(named_dir)
       path_abs = os.path.join(self.root_dir, path)
       if os.path.isdir(path_abs):
         logging.info('Removing named cache %s', path_abs)
         file_path.rmtree(path_abs)
       if min_free_space:
         free_space = file_path.get_free_space(self.root_dir)
       self._lru.pop(name)
+      total += 1
+    return total
 
   _DIR_ALPHABET = string.ascii_letters + string.digits
 
   def _allocate_dir(self):
     """Creates and returns relative path of a new cache directory."""
     # We randomly generate directory names that have two lower/upper case
     # letters or digits. Total number of possibilities is (26*2 + 10)^2 = 3844.
     abc_len = len(self._DIR_ALPHABET)
     tried = set()
     while len(tried) < 1000:
@@ skipping 45 matching lines @@
   if options.named_cache_root:
     return CacheManager(os.path.abspath(options.named_cache_root))
   return None
 
 
 def _validate_named_cache_path(path):
   if os.path.isabs(path):
     raise Error('named cache path must not be absolute')
   if '..' in path.split(os.path.sep):
     raise Error('named cache path must not contain ".."')