Bovlb patch 1 (#2931)

* Update parser.py

Fix SPARQL parsing bug

* Add test for bug fix

* Check imports

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* style

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: bovlb

rdflib/plugins/sparql/parser.py

@@ -59,33 +59,39 @@ def expandTriples(terms: ParseResults) -> List[Any]:
     Expand ; and , syntax for repeat predicates, subjects
     """
     # import pdb; pdb.set_trace()
+    last_subject, last_predicate = None, None  # Used for ; and ,
     try:
         res: List[Any] = []
         if DEBUG:
             print("Terms", terms)
         l_ = len(terms)
         for i, t in enumerate(terms):
             if t == ",":
-                res.extend([res[-3], res[-2]])
+                res.extend([last_subject, last_predicate])
             elif t == ";":
                 if i + 1 == len(terms) or terms[i + 1] == ";" or terms[i + 1] == ".":
                     continue  # this semicolon is spurious
-                res.append(res[0])
+                res.append(last_subject)
             elif isinstance(t, list):
                 # BlankNodePropertyList
                 # is this bnode the object of previous triples?
                 if (len(res) % 3) == 2:
                     res.append(t[0])
                 # is this a single [] ?
                 if len(t) > 1:
-                    res += t
+                    res += t  # Don't update last_subject/last_predicate
                 # is this bnode the subject of more triples?
                 if i + 1 < l_ and terms[i + 1] not in ".,;":
+                    last_subject, last_predicate = t[0], None
                     res.append(t[0])
             elif isinstance(t, ParseResults):
                 res += t.asList()
             elif t != ".":
                 res.append(t)
+                if (len(res) % 3) == 1:
+                    last_subject = t
+                elif (len(res) % 3) == 2:
+                    last_predicate = t
             if DEBUG:
                 print(len(res), t)
         if DEBUG:

test/test_sparql/test_translate_algebra.py

@@ -12,7 +12,7 @@
 
 import rdflib.plugins.sparql.algebra as algebra
 import rdflib.plugins.sparql.parser as parser
-from rdflib import Graph, Literal, URIRef
+from rdflib import Graph, Literal, URIRef, Variable
 from rdflib.plugins.sparql.algebra import translateAlgebra
 from test.data import TEST_DATA_DIR
 
@@ -329,3 +329,20 @@ def test_sparql_group_concat():
     g = Graph()
     q = dict(g.query(query))
     assert q[URIRef("http://example.org/pred")] == Literal("abc")
+
+
+def test_sparql_blank_node_comma():
+    """Tests if blank nodes separated by commas are correctly parsed"""
+
+    query = """
+    PREFIX : <http://example.org/>
+
+    SELECT ?s WHERE {
+    ?s :hasIngredient [:name "chicken"], [:name "butter"] .
+    } LIMIT 10
+    """
+
+    parse_results = parser.parseQuery(query)
+    triples = parse_results[1]["where"].part[0].triples[0]
+    s_count = sum(1 for i in range(0, len(triples), 3) if triples[i] == Variable("s"))
+    assert s_count == 2, f"Found ?s as subject {s_count} times, expected 2"