Avoid raising unrelated AttributeError ... (#2013)

from attempting to access language and datatype attributes of non-Literal objects

Added `isinstance` check to avoid AttributeErrors being raised by attempting to access `language` and `datatype`attribs of non-Literal objects being passed back up the call stack resulting from SPARQL BIND failures/errors.

rdflib/plugins/sparql/operators.py

@@ -298,10 +298,10 @@ def Builtin_CONCAT(expr, ctx):
 
     # dt/lang passed on only if they all match
 
-    dt = set(x.datatype for x in expr.arg)
+    dt = set(x.datatype for x in expr.arg if isinstance(x, Literal))
     dt = dt.pop() if len(dt) == 1 else None
 
-    lang = set(x.language for x in expr.arg)
+    lang = set(x.language for x in expr.arg if isinstance(x, Literal))
     lang = lang.pop() if len(lang) == 1 else None
 
     return Literal("".join(string(x) for x in expr.arg), datatype=dt, lang=lang)

test/test_issues/test_issue1873.py

@@ -0,0 +1,9 @@
+from rdflib import Graph
+
+
+def test_sparql_error_implicit_bind():
+    [r for r in Graph().query('SELECT (concat("", sha1(?x)) AS ?y) WHERE {}')]
+
+
+def test_sparql_error_explicit_bind():
+    [r for r in Graph().query("SELECT ?v ?p ?m WHERE {?v ?p ?m BIND (sha1(?x) AS ?m)}")]