Add client capabilities, enable messages

The API version the client sends can now be used to check what the client
expects or is capable of.

All version tests IPA does will be be named and listed in one module,
ipalib.capabilities, which includes a function to test a specific capability
against an API version.
Similarly to Python's __future__ module, capabilities.py also serves as
documentation of backwards-incompatible changes to the API.

The first capability to be defined is "messages". Recent enough clients can
accept a list of warnings or other info under the "messages" key in the
result dict.

If a JSON client does not send the API version, it is assumed this is a testing
client (e.g. curl from the command line). Such a client "has" all capabilities,
but it will always receive a warning mentioning that forward compatibility
is not guaranteed.
If a XML client does not send the API version, it is assumed it uses the API
version before capabilities were introduced. (This is to keep backwards
compatibility with clients containing bug https://fedorahosted.org/freeipa/ticket/3294)

Whenever a capability is added, the API version must be incremented.
To ensure that, capabilities are written to API.txt and checked by
`makeapi --validate`.

Design page: http://freeipa.org/page/V3/Messages
Ticket: https://fedorahosted.org/freeipa/ticket/2732

1 files changed, 6 insertions, 1 deletions

diff --git a/ipaserver/rpcserver.py b/ipaserver/rpcserver.py
index 581c30b4c..203825ea0 100644
--- a/ipaserver/rpcserver.py
+++ b/ipaserver/rpcserver.py
@@ -35,7 +35,7 @@ import urlparse
 import time
 import json
 
-from ipalib import plugable
+from ipalib import plugable, capabilities
 from ipalib.backend import Executioner
 from ipalib.errors import PublicError, InternalError, CommandError, JSONError, ConversionError, CCacheError, RefererError, InvalidSessionPassword, NotFound, ACIError, ExecutionError
 from ipalib.request import context, Connection, destroy_context
@@ -731,6 +731,11 @@ class xmlserver(WSGIExecutioner, HTTP_Status, KerberosSession):
     def unmarshal(self, data):
         (params, name) = xml_loads(data)
         (args, options) = params_2_args_options(params)
+        if 'version' not in options:
+            # Keep backwards compatibility with client containing
+            # bug https://fedorahosted.org/freeipa/ticket/3294:
+            # If `version` is not given in XML-RPC, assume an old version
+            options['version'] = capabilities.VERSION_WITHOUT_CAPABILITIES
         return (name, args, options, None)
 
     def marshal(self, result, error, _id=None):