support day, month and year function for date

rdflib/plugins/sparql/operators.py

@@ -12,6 +12,7 @@
 import random
 import uuid
 import hashlib
+import datetime as py_datetime  # naming conflict with function within this module
 
 from functools import reduce
 
@@ -449,17 +450,17 @@ def Builtin_NOW(e, ctx):
 
 
 def Builtin_YEAR(e, ctx):
-    d = datetime(e.arg)
+    d = date(e.arg)
     return Literal(d.year)
 
 
 def Builtin_MONTH(e, ctx):
-    d = datetime(e.arg)
+    d = date(e.arg)
     return Literal(d.month)
 
 
 def Builtin_DAY(e, ctx):
-    d = datetime(e.arg)
+    d = date(e.arg)
     return Literal(d.day)
 
 
@@ -998,6 +999,17 @@ def datetime(e):
     return e.toPython()
 
 
+def date(e) -> py_datetime.date:
+    if not isinstance(e, Literal):
+        raise SPARQLError("Non-literal passed as date: %r" % e)
+    if e.datatype not in (XSD.date, XSD.dateTime):
+        raise SPARQLError("Literal with wrong datatype passed as date: %r" % e)
+    result = e.toPython()
+    if isinstance(result, py_datetime.datetime):
+        return result.date()
+    return result
+
+
 def string(s):
     """
     Make sure the passed thing is a string literal

test/test_sparql_operators.py

@@ -0,0 +1,36 @@
+import datetime
+
+import nose.tools
+
+import rdflib
+from rdflib.plugins.sparql import operators
+from rdflib.plugins.sparql import sparql
+
+
+def test_date_cast():
+    now = datetime.datetime.now()
+    today = now.date()
+
+    literal = rdflib.Literal(now)
+    result = operators.date(literal)
+    assert isinstance(result, datetime.date)
+    assert result == today
+
+    literal = rdflib.Literal(today)
+    result = operators.date(literal)
+    assert isinstance(result, datetime.date)
+    assert result == today
+
+
+def test_datetime_cast():
+    now = datetime.datetime.now()
+    literal = rdflib.Literal(now)
+    result = operators.datetime(literal)
+    assert isinstance(result, datetime.datetime)
+    assert result == now
+
+
+@nose.tools.raises(sparql.SPARQLError)
+def test_datetime_cast_type_error():
+    literal = rdflib.Literal("2020-01-02")
+    operators.date(literal)