securesystemslib: Add AnyNonemptyString, use for PATH_SCHEMA

securesystemslib/formats.py

@@ -128,7 +128,7 @@
 SCHEME_SCHEMA = SCHEMA.AnyString()
 
 # A path string, whether relative or absolute, e.g. 'metadata/root/'
-PATH_SCHEMA = SCHEMA.AnyString()
+PATH_SCHEMA = SCHEMA.AnyNonemptyString()
 PATHS_SCHEMA = SCHEMA.ListOf(PATH_SCHEMA)
 
 # An integer representing logger levels, such as logging.CRITICAL (=50).

securesystemslib/schema.py

@@ -208,6 +208,46 @@ def check_match(self, object):
 
 
 
+class AnyNonemptyString(AnyString):
+  """
+  <Purpose>
+    Matches any string with one or more characters.
+    This schema can be viewed as the Any() schema applied to Strings, but an
+    additional check is performed to ensure only strings are considered and
+    that said strings have at least one character.
+
+    Supported methods include:
+      matches(): returns a Boolean result.
+      check_match(): raises 'exceptions.FormatError' on a mismatch.
+
+  <Example Use>
+
+    >>> schema = AnyNonemptyString()
+    >>> schema.matches('')
+    False
+    >>> schema.matches('a string')
+    True
+    >>> schema.matches(['a'])
+    False
+    >>> schema.matches(3)
+    False
+    >>> schema.matches(u'a unicode string')
+    True
+    >>> schema.matches({})
+    False
+  """
+
+  def check_match(self, object):
+    AnyString.check_match(self, object)
+
+    if object == "":
+        raise securesystemslib.exceptions.FormatError('Expected a string'
+            ' with at least one character but got ' + repr(object))
+
+
+
+
+
 class AnyBytes(Schema):
   """
   <Purpose>

securesystemslib/util.py

@@ -210,7 +210,7 @@ def file_in_confined_directories(filepath, confined_directories):
   # Do the arguments have the correct format?
   # Raise 'securesystemslib.exceptions.FormatError' if there is a mismatch.
   securesystemslib.formats.PATH_SCHEMA.check_match(filepath)
-  securesystemslib.formats.PATHS_SCHEMA.check_match(confined_directories)
+  securesystemslib.formats.NAMES_SCHEMA.check_match(confined_directories)
 
   for confined_directory in confined_directories:
     # The empty string (arbitrarily chosen) signifies the client is confined

tests/test_schema.py

@@ -131,6 +131,19 @@ def test_AnyString(self):
 
 
 
+  def test_AnyNonemptyString(self):
+    anynonemptystring_schema = SCHEMA.AnyNonemptyString()
+
+    self.assertTrue(anynonemptystring_schema.matches("foo"))
+
+    # Test conditions for invalid arguments.
+    self.assertFalse(anynonemptystring_schema.matches(''))
+    self.assertFalse(anynonemptystring_schema.matches(['a']))
+    self.assertFalse(anynonemptystring_schema.matches(3))
+    self.assertFalse(anynonemptystring_schema.matches({'a': 'string'}))
+
+
+
   def test_OneOf(self):
     # Test conditions for valid arguments.
     oneof_schema = SCHEMA.OneOf([SCHEMA.ListOf(SCHEMA.Integer()),