Merge pull request #592 from joernhees/fix_554

SPARQL select nothing no longer returns a `None` row

rdflib/query.py

@@ -256,12 +256,14 @@ def __iter__(self):
 
             if self._genbindings:
                 for b in self._genbindings:
-                    self._bindings.append(b)
-                    yield ResultRow(b, self.vars)
+                    if b:  # don't add a result row in case of empty binding {}
+                        self._bindings.append(b)
+                        yield ResultRow(b, self.vars)
                 self._genbindings = None
             else:
                 for b in self._bindings:
-                    yield ResultRow(b, self.vars)
+                    if b:  # don't add a result row in case of empty binding {}
+                        yield ResultRow(b, self.vars)
 
     def __getattr__(self, name):
         if self.type in ("CONSTRUCT", "DESCRIBE") and self.graph is not None:

test/test_initbindings.py

@@ -101,15 +101,15 @@ def testDistinctOrderByLimit():
 def testPrepare():
     q = prepareQuery('SELECT ?target WHERE { }')
     r = list(g.query(q))
-    e = [(None,)] # TODO: https://github.com/RDFLib/rdflib/issues/554
+    e = []
     assert r == e, 'prepare: %r != %r'%(r,e)
 
     r = list(g.query(q, initBindings={'target': Literal('example')}))
     e = [(Literal('example'),)]
     assert r == e, 'prepare: %r != %r'%(r, e)
 
     r = list(g.query(q))
-    e = [(None,)] # TODO: https://github.com/RDFLib/rdflib/issues/554
+    e = []
     assert r == e, 'prepare: %r != %r'%(r,e)
 
 

test/test_issue554.py

@@ -0,0 +1,14 @@
+# test for https://github.com/RDFLib/rdflib/issues/554
+
+import rdflib
+
+def test_sparql_empty_no_row():
+    g = rdflib.Graph()
+    q = 'select ?whatever { }'
+    r = list(g.query(q))
+    assert r == [], \
+        'sparql query %s should return empty list but returns %s' % (q, r)
+
+
+if __name__ == '__main__':
+    test_sparql_empty_no_row()