Merge pull request #978 from RDFLib/pr_451_redux

Fix adding together literals, always get the expected datatype out.

2 files changed, 126 insertions, 6 deletions

diff --git a/rdflib/term.py b/rdflib/term.py
index 8f3c8e6f..3d290258 100644
--- a/rdflib/term.py
+++ b/rdflib/term.py
@@ -644,15 +644,45 @@ class Literal(Identifier):
         rdflib.term.Literal(u'11')
         """
 
-        py = self.toPython()
-        if not isinstance(py, Literal):
+        # if no val is supplied, return this Literal
+        if val is None:
+            return self
+
+        # convert the val to a Literal, if it isn't already one
+        if not isinstance(val, Literal):
+            val = Literal(val)
+
+        # if the datatypes are the same, just add the Python values and convert back
+        if self.datatype == val.datatype:
+            return Literal(self.toPython() + val.toPython(), self.language, datatype=self.datatype)
+        # if the datatypes are not the same but are both numeric, add the Python values and strip off decimal junk
+        # (i.e. tiny numbers (more than 17 decimal places) and trailing zeros) and return as a decimal
+        elif (
+                self.datatype in _NUMERIC_LITERAL_TYPES
+                and
+                val.datatype in _NUMERIC_LITERAL_TYPES
+        ):
+            return Literal(
+                Decimal(
+                    ('%f' % round(Decimal(self.toPython()) + Decimal(val.toPython()), 15)).rstrip('0').rstrip('.')
+                ),
+                datatype=_XSD_DECIMAL
+            )
+        # in all other cases, perform string concatenation
+        else:
             try:
-                return Literal(py + val)
+                s = text_type.__add__(self, val)
             except TypeError:
-                pass  # fall-through
+                s = str(self.value) + str(val)
+
+            # if the original datatype is string-like, use that
+            if self.datatype in _STRING_LITERAL_TYPES:
+                new_datatype = self.datatype
+            # if not, use string
+            else:
+                new_datatype = _XSD_STRING
 
-        s = text_type.__add__(self, val)
-        return Literal(s, self.language, self.datatype)
+            return Literal(s, self.language, datatype=new_datatype)
 
     def __bool__(self):
         """
@@ -1434,6 +1464,15 @@ _TOTAL_ORDER_CASTERS = {
 }
 
 
+_STRING_LITERAL_TYPES = (
+    _XSD_STRING,
+    _RDF_XMLLITERAL,
+    _RDF_HTMLLITERAL,
+    URIRef(_XSD_PFX + 'normalizedString'),
+    URIRef(_XSD_PFX + 'token')
+)
+
+
 def _py2literal(obj, pType, castFunc, dType):
     if castFunc:
         return castFunc(obj), dType
diff --git a/test/test_term.py b/test/test_term.py
index c222a8d2..4dea9c3c 100644
--- a/test/test_term.py
+++ b/test/test_term.py
@@ -123,6 +123,87 @@ class TestLiteral(unittest.TestCase):
         random.shuffle(l2)
         self.assertListEqual(l1, sorted(l2))
 
+    def test_literal_add(self):
+        from decimal import Decimal
+
+        # compares Python decimals
+        def isclose(a, b, rel_tol=1e-09, abs_tol=0.0):
+            a = float(a)
+            b = float(b)
+            return abs(a - b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)
+
+        cases = [
+            (1, Literal(1), Literal(1), Literal(2)),
+            (2, Literal(Decimal(1)), Literal(Decimal(1)), Literal(Decimal(2))),
+            (3, Literal(float(1)), Literal(float(1)), Literal(float(2))),
+            (4, Literal(1), Literal(1.1), Literal(2.1, datatype=XSD.decimal)),
+            (5, Literal(1.1), Literal(1.1), Literal(2.2)),
+            (6, Literal(Decimal(1)), Literal(Decimal(1.1)), Literal(Decimal(2.1), datatype=XSD.decimal)),
+            (7, Literal(Decimal(1.1)), Literal(Decimal(1.1)), Literal(Decimal(2.2))),
+            (8, Literal(float(1)), Literal(float(1.1)), Literal(float(2.1))),
+            (9, Literal(float(1.1)), Literal(float(1.1)), Literal(float(2.2))),
+            (10, Literal(-1), Literal(-1), Literal(-2)),
+            (12, Literal(Decimal(-1)), Literal(Decimal(-1)), Literal(Decimal(-2))),
+            (13, Literal(float(-1)), Literal(float(-1)), Literal(float(-2))),
+            (14, Literal(-1), Literal(-1.1), Literal(-2.1)),
+            (15, Literal(-1.1), Literal(-1.1), Literal(-2.2)),
+            (16, Literal(Decimal(-1)), Literal(Decimal(-1.1)), Literal(Decimal(-2.1))),
+            (17, Literal(Decimal(-1.1)), Literal(Decimal(-1.1)), Literal(Decimal(-2.2))),
+            (18, Literal(float(-1)), Literal(float(-1.1)), Literal(float(-2.1))),
+            (19, Literal(float(-1.1)), Literal(float(-1.1)), Literal(float(-2.2))),
+
+            (20, Literal(1), Literal(1.0), Literal(2.0)),
+            (21, Literal(1.0), Literal(1.0), Literal(2.0)),
+            (22, Literal(Decimal(1)), Literal(Decimal(1.0)), Literal(Decimal(2.0))),
+            (23, Literal(Decimal(1.0)), Literal(Decimal(1.0)), Literal(Decimal(2.0))),
+            (24, Literal(float(1)), Literal(float(1.0)), Literal(float(2.0))),
+            (25, Literal(float(1.0)), Literal(float(1.0)), Literal(float(2.0))),
+
+            (26, Literal(1, datatype=XSD.integer), Literal(1, datatype=XSD.integer), Literal(2, datatype=XSD.integer)),
+            (27, Literal(1, datatype=XSD.integer), Literal("1", datatype=XSD.integer), Literal("2", datatype=XSD.integer)),
+            (28, Literal("1", datatype=XSD.integer), Literal("1", datatype=XSD.integer), Literal("2", datatype=XSD.integer)),
+            (29, Literal("1"), Literal("1", datatype=XSD.integer), Literal("11", datatype=XSD.string)),
+            (30, Literal(1), Literal("1", datatype=XSD.integer), Literal("2", datatype=XSD.integer)),
+            (31, Literal(Decimal(1), datatype=XSD.decimal), Literal(Decimal(1), datatype=XSD.decimal), Literal(Decimal(2), datatype=XSD.decimal)),
+            (32, Literal(Decimal(1)), Literal(Decimal(1), datatype=XSD.decimal), Literal(Decimal(2), datatype=XSD.decimal)),
+            (33, Literal(float(1)), Literal(float(1), datatype=XSD.float), Literal(float(2), datatype=XSD.float)),
+            (34, Literal(float(1), datatype=XSD.float), Literal(float(1), datatype=XSD.float), Literal(float(2), datatype=XSD.float)),
+
+            (35, Literal(1), 1, Literal(2)),
+            (36, Literal(1), 1.0, Literal(2, datatype=XSD.decimal)),
+            (37, Literal(1.0), 1, Literal(2, datatype=XSD.decimal)),
+            (38, Literal(1.0), 1.0, Literal(2.0)),
+            (39, Literal(Decimal(1.0)), Decimal(1), Literal(Decimal(2.0))),
+            (40, Literal(Decimal(1.0)), Decimal(1.0), Literal(Decimal(2.0))),
+            (41, Literal(float(1.0)), float(1), Literal(float(2.0))),
+            (42, Literal(float(1.0)), float(1.0), Literal(float(2.0))),
+
+            (43, Literal(1, datatype=XSD.integer), "+1.1", Literal("1+1.1", datatype=XSD.string)),
+            (44, Literal(1, datatype=XSD.integer), Literal("+1.1", datatype=XSD.string), Literal("1+1.1", datatype=XSD.string)),
+            (45, Literal(Decimal(1.0), datatype=XSD.integer), Literal(u"1", datatype=XSD.string), Literal("11", datatype=XSD.string)),
+            (46, Literal(1.1, datatype=XSD.integer), Literal("1", datatype=XSD.string), Literal("1.11", datatype=XSD.string)),
+
+            (47, Literal(1, datatype=XSD.integer), None, Literal(1, datatype=XSD.integer)),
+            (48, Literal("1", datatype=XSD.string), None, Literal("1", datatype=XSD.string)),
+        ]
+
+        for case in cases:
+            # see if the addition exactly matches the expected output
+            case_passed = (case[1] + case[2]) == (case[3])
+            # see if the addition almost matches the expected output, for decimal precision errors
+            if not case_passed:
+                try:
+                    case_passed = isclose((case[1] + case[2].value), case[3].value)
+                except:
+                    pass
+
+            if not case_passed:
+                print(case[1], case[2])
+                print("expected: " + case[3] + ", " + case[3].datatype)
+                print("actual: " + (case[1] + case[2]) + ", " + (case[1] + case[2]).datatype)
+
+            self.assertTrue(case_passed, "Case " + str(case[0]) + " failed")
+
 
 class TestValidityFunctions(unittest.TestCase):