Don't allow to use float in Numeric fields

The goal is to prevent to introduce float errors in Numeric fields.
There is a trick for external protocols like XML-RPC and JSON-RPC where the
string representation is stored in the Float object and will be used to
convert it into Decimal.

CHANGELOG

@@ -1,3 +1,4 @@
+* Don't allow to use float in Numeric fields
 * set/get function on Fields take a list of ids
 * New interface for Function/Property fields
   Take a Field as first argument instead of many separate arguments

trytond/backend/fields.py

@@ -79,8 +79,10 @@ class Numeric(Float):
     def sql_format(value):
         if not value:
             value = Decimal('0.0')
-        if isinstance(value, (int, long, float)):
+        if isinstance(value, (int, long)):
             value = Decimal(repr(value))
+        if isinstance(value, float) and hasattr(value, 'decimal'):
+            value = Decimal(value.decimal)
         assert isinstance(value, Decimal)
         return value
 

trytond/protocols/datatype.py

@@ -0,0 +1,18 @@
+#This file is part of Tryton.  The COPYRIGHT file at the top level of
+#this repository contains the full copyright notices and license terms.
+
+class Float(float):
+
+    def __init__(self, value):
+        super(Float, self).__init__()
+        self.__decimal = value
+
+    @property
+    def decimal(self):
+        return self.__decimal
+
+    def __repr__(self):
+        return self.decimal
+
+    def __str__(self):
+        return self.decimal

trytond/protocols/jsonrpc.py

@@ -3,6 +3,7 @@
 from trytond.protocols.sslsocket import SSLSocket
 from trytond.protocols.dispatcher import dispatch
 from trytond.config import CONFIG
+from trytond.protocols.datatype import Float
 import SimpleXMLRPCServer
 import SimpleHTTPServer
 import SocketServer
@@ -77,7 +78,7 @@ class SimpleJSONRPCDispatcher(SimpleXMLRPCServer.SimpleXMLRPCDispatcher):
         existing method through subclassing is the prefered means
         of changing method dispatch behavior.
         """
-        rawreq = json.loads(data, object_hook=object_hook)
+        rawreq = json.loads(data, object_hook=object_hook, parse_float=Float)
 
         req_id = rawreq.get('id', 0)
         method = rawreq['method']

trytond/protocols/xmlrpc.py

@@ -3,6 +3,7 @@
 from trytond.protocols.sslsocket import SSLSocket
 from trytond.protocols.dispatcher import dispatch
 from trytond.config import CONFIG
+from trytond.protocols.datatype import Float
 import SimpleXMLRPCServer
 import SocketServer
 import xmlrpclib
@@ -21,6 +22,11 @@ xmlrpclib.Marshaller.dispatch[Decimal] = \
 xmlrpclib.Marshaller.dispatch[type(None)] = \
         lambda self, value, write: self.dump_bool(bool(value), write)
 
+def _end_double(self, data):
+    self.append(Float(data))
+    self._value = 0
+xmlrpclib.Unmarshaller.dispatch["double"] = _end_double
+
 
 class GenericXMLRPCRequestHandler: