Use expected XSD spellings for xsi:double infinity and NaN (GH-338)

W3C specification for xsd:double says
> The special values positive and negative infinity and
> not-a-number have lexical representations INF, -INF and NaN,
> respectively.

Thus case matters. The previously used float.__repr__ would generate
"inf", "-inf", "nan". Now we prepend special handling to get
"INF", "-INF", "NaN" instead (which is still pytype compatible).

Includes minor non-functional alignments of related bool to text code,
and tests to assert its XML schema conformance as well.

src/lxml/objectify.pyx

@@ -38,6 +38,9 @@ import_lxml__etree()
 
 __version__ = etree.__version__
 
+cdef object _float_is_inf, _float_is_nan
+from math import isinf as _float_is_inf, isnan as _float_is_nan
+
 cdef object re
 import re
 
@@ -1205,8 +1208,17 @@ cdef dict _PYTYPE_DICT = {}
 cdef dict _SCHEMA_TYPE_DICT = {}
 cdef list _TYPE_CHECKS = []
 
-cdef unicode _lower_bool(b):
-    return u"true" if b else u"false"
+cdef unicode _xml_bool(value):
+    return u"true" if value else u"false"
+
+cdef unicode _xml_float(value):
+    if _float_is_inf(value):
+        if value > 0:
+            return u"INF"
+        return u"-INF"
+    if _float_is_nan(value):
+        return u"NaN"
+    return unicode(repr(value))
 
 cdef _pytypename(obj):
     return u"str" if python._isString(obj) else _typename(obj)
@@ -1230,11 +1242,11 @@ cdef _registerPyTypes():
     pytype = PyType(u'long', None, IntElement)
     pytype.register()
 
-    pytype = PyType(u'float', _checkFloat, FloatElement, repr)  # wraps _parseFloat for Python
+    pytype = PyType(u'float', _checkFloat, FloatElement, _xml_float)  # wraps functions for Python
     pytype.xmlSchemaTypes = (u"double", u"float")
     pytype.register()
 
-    pytype = PyType(u'bool', _checkBool, BoolElement, _lower_bool)  # wraps functions for Python
+    pytype = PyType(u'bool', _checkBool, BoolElement, _xml_bool)  # wraps functions for Python
     pytype.xmlSchemaTypes = (u"boolean",)
     pytype.register()
 

src/lxml/tests/test_objectify.py

@@ -873,6 +873,10 @@ def test_data_element_bool(self):
         self.assertTrue(isinstance(value, objectify.BoolElement))
         self.assertEqual(value, False)
 
+    def test_data_element_bool_text(self):
+        self.assertEqual(objectify.DataElement(False).text, "false")
+        self.assertEqual(objectify.DataElement(True).text, "true")
+
     def test_type_str(self):
         Element = self.Element
         SubElement = self.etree.SubElement
@@ -1115,6 +1119,11 @@ def test_data_element_float_hash_repr(self):
         value = objectify.DataElement(f)
         self.assertEqual(hash(value), hash(f))
 
+    def test_data_element_float_special_value_text(self):
+        self.assertEqual(objectify.DataElement(float("inf")).text, "INF")
+        self.assertEqual(objectify.DataElement(float("-inf")).text, "-INF")
+        self.assertEqual(objectify.DataElement(float("nan")).text, "NaN")
+
     def test_data_element_xsitypes(self):
         for xsi, objclass in xsitype2objclass.items():
             # 1 is a valid value for all ObjectifiedDataElement classes