Fix losing float precision for lxml.objectify FloatElement.

Use repr() instead of str()/unicode() as 'stringification' function in the
FloatElement type registration.

2 files changed, 53 insertions, 6 deletions

diff --git a/src/lxml/lxml.objectify.pyx b/src/lxml/lxml.objectify.pyx
index 371eb2c5..d79fcd82 100644
--- a/src/lxml/lxml.objectify.pyx
+++ b/src/lxml/lxml.objectify.pyx
@@ -896,11 +896,14 @@ cdef class PyType:
     u"""PyType(self, name, type_check, type_class, stringify=None)
     User defined type.
 
-    Named type that contains a type check function and a type class that
-    inherits from ObjectifiedDataElement.  The type check must take a string
-    as argument and raise ValueError or TypeError if it cannot handle the
-    string value.  It may be None in which case it is not considered for type
-    guessing.
+    Named type that contains a type check function, a type class that
+    inherits from ObjectifiedDataElement and an optional "stringification"
+    function.  The type check must take a string as argument and raise
+    ValueError or TypeError if it cannot handle the string value.  It may be
+    None in which case it is not considered for type guessing.  For registered
+    named types, the 'stringify' function (or unicode() if None) is used to
+    convert a Python object with type name 'name' to the string representation
+    stored in the XML tree.
 
     Example::
 
@@ -1031,7 +1034,7 @@ cdef _registerPyTypes():
     pytype = PyType(u'long', None, IntElement)
     pytype.register()
 
-    pytype = PyType(u'float', float, FloatElement)
+    pytype = PyType(u'float', float, FloatElement, repr)
     pytype.xmlSchemaTypes = (u"double", u"float")
     pytype.register()
 
diff --git a/src/lxml/tests/test_objectify.py b/src/lxml/tests/test_objectify.py
index b17e38c2..68b9d7a8 100644
--- a/src/lxml/tests/test_objectify.py
+++ b/src/lxml/tests/test_objectify.py
@@ -1016,6 +1016,50 @@ class ObjectifyTestCase(HelperTestCase):
         value = objectify.DataElement(5.5)
         self.assertEqual(hash(value), hash(5.5))
 
+    def test_type_float_precision(self):
+        # test not losing precision by shortened float str() value
+        # repr(2.305064300557): '2.305064300557'
+        # str(2.305064300557): '2.30506430056'
+        # "%57.54f" % 2.305064300557:
+        #     ' 2.305064300556999956626214043353684246540069580078125000'
+        Element = self.Element
+        root = Element("{objectified}root")
+        s = "2.305064300557"
+        root.f = float(s)
+        self.assertTrue(isinstance(root.f, objectify.FloatElement))
+        self.assertEqual(root.f.text, s)
+        self.assertEqual(root.f.pyval, float(s))
+
+    def test_type_float_instantiation_precision(self):
+        # test precision preservation for FloatElement instantiation
+        s = "2.305064300557"
+        self.assertEqual(objectify.FloatElement(s), float(s))
+  
+    def test_type_float_precision_consistency(self):
+        # test consistent FloatElement values for the different instantiation
+        # possibilities
+        Element = self.Element
+        root = Element("{objectified}root")
+        s = "2.305064300557"
+        f = float(s)
+        float_elem = objectify.FloatElement(s)
+        float_data_elem = objectify.DataElement(f)
+        root.float_child = float(f)
+        self.assertTrue(f == float_elem == float_data_elem == root.float_child)
+
+    def test_data_element_float_precision(self):
+        # test not losing precision by shortened float str() value
+        f = 2305064300557.0
+        value = objectify.DataElement(f)
+        self.assertTrue(isinstance(value, objectify.FloatElement))
+        self.assertEqual(value, f)
+
+    def test_data_element_float_hash_repr(self):
+        # test not losing precision by shortened float str() value
+        f = 2305064300557.0
+        value = objectify.DataElement(f)
+        self.assertEqual(hash(value), hash(f))
+
     def test_data_element_xsitypes(self):
         for xsi, objclass in xsitype2objclass.items():
             # 1 is a valid value for all ObjectifiedDataElement classes