attempt to fix #633

2 files changed, 75 insertions, 2 deletions

diff --git a/rdflib/plugins/sparql/evaluate.py b/rdflib/plugins/sparql/evaluate.py
index e558a825..48abc962 100644
--- a/rdflib/plugins/sparql/evaluate.py
+++ b/rdflib/plugins/sparql/evaluate.py
@@ -141,8 +141,10 @@ def evalLeftJoin(ctx, join):
             # before we yield a solution without the OPTIONAL part
             # check that we would have had no OPTIONAL matches
             # even without prior bindings...
-            if not any(_ebv(join.expr, b) for b in
-                       evalPart(ctx.thaw(a.remember(join.p1._vars)), join.p2)):
+            p1_vars = join.p1._vars
+            if p1_vars is None \
+            or not any(_ebv(join.expr, b) for b in
+                       evalPart(ctx.thaw(a.remember(p1_vars)), join.p2)):
 
                 yield a
 
diff --git a/test-update.py b/test-update.py
new file mode 100644
index 00000000..b324f5d8
--- /dev/null
+++ b/test-update.py
@@ -0,0 +1,71 @@
+from rdflib import *
+
+ex = Namespace('http://ex.co/')
+g = Graph()
+g.namespace_manager.bind('', ex)
+
+g.add((ex.s1, ex.p, ex.o1))
+g.add((ex.s1, ex.p, ex.o2))
+g.add((ex.s1, ex.p, ex.o3))
+
+g.add((ex.s2, ex.p, ex.o2))
+g.add((ex.s2, ex.p, ex.o3))
+g.add((ex.s2, ex.p, ex.o4))
+g.add((ex.s2, ex.p, ex.o5))
+
+g.add((ex.s3, ex.p, ex.o1))
+g.add((ex.s3, ex.p, ex.o3))
+g.add((ex.s3, ex.p, ex.o5))
+
+
+print(g.serialize(format="n3"))
+
+# should be
+#    :s1 :p :o1, :o2, :o3 .
+#    :s2 :p :o2, :o3, :o4, :o5 .
+#    :s3 :p :o1, :o3, :o5 .
+
+print '---'
+
+print(g.query("""
+PREFIX : <http://ex.co/>
+
+SELECT ?o ?new
+WHERE {
+  :s1 :p ?o .
+  :s2 :p ?o .
+  OPTIONAL {
+    :s3 :p ?o .
+    BIND(:s4 as ?new)
+  }
+}
+""").serialize(format="csv"))
+
+# should be
+#    :o2 ,
+#    :o3 , :s4
+
+print '---'
+
+g.update("""
+PREFIX : <http://ex.co/>
+
+DELETE { :s1 :p ?o }
+INSERT { ?new :p ?o }
+WHERE {
+  :s1 :p ?o .
+  :s2 :p ?o .
+  OPTIONAL {
+    :s3 :p ?o .
+    BIND(:s4 as ?new)
+  }
+}
+""")
+
+print(g.serialize(format="n3"))
+
+# should now be
+#    :s1 :p :o1 .
+#    :s2 :p :o2, :o3, :o4, :o5 .
+#    :s3 :p :o1, :o3, :o5 .
+#    :s4 :p :o3 .