Merge pull request #260 from MVrachev/fix-empty-directory

Fix directory being empty in ensure_parent_dir

securesystemslib/util.py

@@ -254,7 +254,10 @@ def ensure_parent_dir(filename, storage_backend=None):
   # Split 'filename' into head and tail, check if head exists.
   directory = os.path.split(filename)[0]
 
-  storage_backend.create_folder(directory)
+  # Check for cases where filename is without directory like 'file.txt'
+  # and as a result directory is an empty string
+  if directory:
+    storage_backend.create_folder(directory)
 
 
 def file_in_confined_directories(filepath, confined_directories):

tests/test_util.py

@@ -153,6 +153,13 @@ def  test_B4_ensure_parent_dir(self):
         self.assertRaises(securesystemslib.exceptions.FormatError,
             securesystemslib.util.ensure_parent_dir, parent_dir)
 
+    # When we call ensure_parent_dir with filepath arg like "a.txt",
+    # then the directory of that filepath will be an empty string.
+    # We want to make sure that securesyslib.storage.create_folder()
+    # won't be called with an empty string and thus raise an exception.
+    # If an exception is thrown the test will fail.
+    securesystemslib.util.ensure_parent_dir('a.txt')
+
 
 
   def  test_B5_file_in_confined_directories(self):