Allow custom server backend encoding

Server framework does not support encoding of native Python type
values stored in Param classes and sub-classes. When backend (LDAP)
value encoding differs from Python type value representation user
has to has to hard-code the encoders in his processing.

This patch introduces a method Param.encode which is used in server
context to encode native Python Param values. The new encode method
is used for Bool parameter to convert native Python bool type value
(True, False) to LDAP value ("TRUE", "FALSE").

https://fedorahosted.org/freeipa/ticket/2039

ipalib/frontend.py

@@ -428,6 +428,8 @@ class Command(HasParam):
         if not self.api.env.in_server and 'version' not in params:
             params['version'] = API_VERSION
         self.validate(**params)
+        if self.api.env.in_server:
+            params = self.encode(**params)
         (args, options) = self.params_2_args_options(**params)
         ret = self.run(*args, **options)
         if (
@@ -648,6 +650,14 @@ class Command(HasParam):
             (k, self.params[k].convert(v)) for (k, v) in kw.iteritems()
         )
 
+    def encode(self, **kw):
+        """
+        Return a dictionary of encoded values.
+        """
+        return dict(
+            (k, self.params[k].encode(v)) for (k, v) in kw.iteritems()
+        )
+
     def __convert_iter(self, kw):
         for param in self.params():
             if kw.get(param.name, None) is None:

ipalib/parameters.py

@@ -307,6 +307,7 @@ class Param(ReadOnly):
         ('multivalue', bool, False),
         ('primary_key', bool, False),
         ('normalizer', callable, None),
+        ('encoder', callable, None),
         ('default_from', DefaultFrom, None),
         ('create_default', callable, None),
         ('autofill', bool, False),
@@ -768,6 +769,34 @@ class Param(ReadOnly):
                     rule=rule,
                 )
 
+    def encode(self, value):
+        """
+        Encode Python native type value to chosen backend format. Encoding is
+        applied for parameters representing actual attributes (attribute=True).
+
+        The default encode method `Param._encode` can be overriden in a `Param`
+        instance with `encoder` attribute:
+
+        >>> s = Str('my_str', encoder=lambda x:encode(x))
+
+        Note that the default method of encoding values is defined in
+        `Param._encode()`.
+
+        :param value: Encoded value
+        """
+        if not self.attribute: #pylint: disable=E1101
+            return value
+        if self.encoder is not None: #pylint: disable=E1101
+            return self.encoder(value) #pylint: disable=E1101
+
+        return self._encode(value)
+
+    def _encode(self, value):
+        """
+        Encode a value to backend format.
+        """
+        return value
+
     def get_default(self, **kw):
         """
         Return the static default or construct and return a dynamic default.

ipaserver/plugins/ldap2.py

@@ -45,6 +45,7 @@ from ldap.controls import LDAPControl
 from ldap.functions import explode_dn
 from ipalib.dn import DN
 from ipalib import _
+from ipalib.parameters import Bool
 
 import krbV
 
@@ -62,6 +63,22 @@ MEMBERS_INDIRECT = 2
 # SASL authentication mechanism
 SASL_AUTH = _ldap_sasl.sasl({}, 'GSSAPI')
 
+# OID 1.3.6.1.4.1.1466.115.121.1.7 (Boolean) syntax encoding
+def _encode_bool(self, value):
+    def encode_bool_value(value):
+        if value:
+            return u'TRUE'
+        else:
+            return u'FALSE'
+
+    if type(value) in (tuple, list):
+        return tuple(encode_bool_value(v) for v in value)
+    else:
+        return encode_bool_value(value)
+
+# set own Bool parameter encoder
+Bool._encode = _encode_bool
+
 # universal LDAPError handler
 def _handle_errors(e, **kw):
     """