Add max_length to URIOpt

Currently StrOpt has a max_length parameter to restrict the length
of the value, but URIOpt does not. The keystone project actually
has use for a max_length to restrict a URI used for the SAML2
entity ID.

Reference patch:
https://review.openstack.org/#/c/341514

Change-Id: I39d012b0b7ebeddf6067016487ac8258461dda30

oslo_config/cfg.py

@@ -1283,11 +1283,19 @@ class URIOpt(Opt):
 
     Option with ``type`` :class:`oslo_config.types.URI`
 
+    :param max_length: If positive integer, the value must be less than or
+                       equal to this parameter.
+
     .. versionadded:: 3.12
+
+    .. versionchanged:: 3.14
+       Added *max_length* parameter
     """
 
-    def __init__(self, name, **kwargs):
-        super(URIOpt, self).__init__(name, type=types.URI(), **kwargs)
+    def __init__(self, name, max_length=None, **kwargs):
+        super(URIOpt, self).__init__(name,
+                                     type=types.URI(max_length=max_length),
+                                     **kwargs)
 
 
 class MultiOpt(Opt):

oslo_config/tests/test_cfg.py

@@ -4327,6 +4327,19 @@ class StrOptMaxLengthTestCase(BaseTestCase):
         self.assertRaises(SystemExit, self.conf, ['--foo', '123456'])
 
 
+class URIOptMaxLengthTestCase(BaseTestCase):
+
+    def test_uriopt_max_length_good(self):
+        self.conf.register_cli_opt(cfg.URIOpt('foo', max_length=30))
+        self.conf(['--foo', 'http://www.example.com'])
+        self.assertEqual('http://www.example.com', self.conf.foo)
+
+    def test_uriopt_max_length_bad(self):
+        self.conf.register_cli_opt(cfg.URIOpt('foo', max_length=30))
+        self.assertRaises(SystemExit, self.conf,
+                          ['--foo', 'http://www.example.com/versions'])
+
+
 class PrintHelpTestCase(base.BaseTestCase):
 
     def test_print_help_without_init(self):

oslo_config/tests/test_types.py

@@ -649,3 +649,9 @@ class URITypeTests(TypeTestHelper, unittest.TestCase):
 
     def test_repr(self):
         self.assertEqual('URI', repr(types.URI()))
+
+    def test_max_length(self):
+        self.type_instance = types.String(max_length=30)
+        self.assertInvalid('http://www.example.com/versions')
+        self.assertConvertedValue('http://www.example.com',
+                                  'http://www.example.com')

oslo_config/types.py

@@ -665,16 +665,27 @@ class URI(ConfigType):
     Represents URI. Value will be validated as RFC 3986.
 
     :param type_name: Type name to be used in the sample config file.
+    :param max_length: Optional integer. If a positive value is specified,
+                       a maximum length of an option value must be less than
+                       or equal to this parameter. Otherwise no length check
+                       will be done.
 
+    .. versionchanged:: 3.14
+       Added *max_length* parameter.
     """
 
-    def __init__(self, type_name='uri value'):
+    def __init__(self, max_length=None, type_name='uri value'):
         super(URI, self).__init__(type_name=type_name)
+        self.max_length = max_length
 
     def __call__(self, value):
         if not rfc3986.is_valid_uri(value, require_scheme=True,
                                     require_authority=True):
             raise ValueError('invalid URI: %r' % value)
+
+        if self.max_length is not None and len(value) > self.max_length:
+            raise ValueError("Value '%s' exceeds maximum length %d" %
+                             (value, self.max_length))
         self.value = value
         return value