slapgrid: Refactor iterating over dir entries

slapos/grid/promise/__init__.py

@@ -44,7 +44,7 @@ import hashlib
 from datetime import datetime
 from multiprocessing import Process, Queue as MQueue
 from six.moves import queue, reload_module
-from slapos.util import str2bytes, mkdir_p, chownDirectory
+from slapos.util import str2bytes, mkdir_p, chownDirectory, listifdir
 from slapos.grid.utils import dropPrivileges, killProcessTree
 from slapos.grid.promise import interface
 from slapos.grid.promise.generic import (GenericPromise, PromiseQueueResult,
@@ -731,10 +731,8 @@ class PromiseLauncher(object):
     error = 0
     success = 0
     promise_name_list = []
-    if os.path.exists(self.promise_folder) and os.path.isdir(self.promise_folder):
-      for promise_name in os.listdir(self.promise_folder):
-        for suffix in ['.pyc', '.pyo']:
-          if promise_name.endswith(suffix):
+    for promise_name in listifdir(self.promise_folder):
+      if promise_name.endswith(('.pyc', '.pyo')):
         promise_path = os.path.join(self.promise_folder, promise_name)
         if not os.path.exists(promise_path[:-1]):
           try:
@@ -816,10 +814,9 @@ class PromiseLauncher(object):
         if key not in promise_name_list:
           new_state_dict.pop(key, None)
 
-    if not self.run_only_promise_list and os.path.exists(self.legacy_promise_folder) \
-        and os.path.isdir(self.legacy_promise_folder):
+    if not self.run_only_promise_list:
       # run legacy promise styles
-      for promise_name in os.listdir(self.legacy_promise_folder):
+      for promise_name in listifdir(self.legacy_promise_folder):
         promise_path = os.path.join(self.legacy_promise_folder, promise_name)
         if not os.path.isfile(promise_path) or \
             not os.access(promise_path, os.X_OK):

slapos/grid/slapgrid.py

@@ -55,7 +55,7 @@ from slapos import manager as slapmanager
 from slapos.slap.slap import NotFoundError
 from slapos.slap.slap import ServerError
 from slapos.slap.slap import COMPUTER_PARTITION_REQUEST_LIST_TEMPLATE_FILENAME
-from slapos.util import mkdir_p, chownDirectory, string_to_boolean
+from slapos.util import mkdir_p, chownDirectory, string_to_boolean, listifdir
 from slapos.grid.exception import BuildoutFailedError
 from slapos.grid.SlapObject import Software, Partition
 from slapos.grid.svcbackend import (launchSupervisord,
@@ -1596,10 +1596,7 @@ stderr_logfile_backups=1
         instance_path = os.path.join(self.instance_root,
             computer_partition.getId())
         report_path = os.path.join(instance_path, 'etc', 'report')
-        if os.path.isdir(report_path):
-          script_list_to_run = os.listdir(report_path)
-        else:
-          script_list_to_run = []
+        script_list_to_run = listifdir(report_path)
 
         # We now generate the pseudorandom name for the xml file
         # and we add it in the invocation_list

slapos/util.py

@@ -95,6 +95,18 @@ def mkdir_p(path, mode=0o700):
             raise
 
 
+def listifdir(path):
+  """
+  Like listdir, but returns an empty tuple if the path is not a directory.
+  """
+  try:
+    return os.listdir(path)
+  except OSError as e:
+    if e.errno != errno.ENOENT:
+      raise
+    return ()
+
+
 def chownDirectory(path, uid, gid):
   if os.getuid() != 0:
     # we are probably inside of a webrunner