Added test for Issue 682 and fixed.

2 files changed, 40 insertions, 3 deletions

diff --git a/rdflib/compare.py b/rdflib/compare.py
index fb9b1902..bf311438 100644
--- a/rdflib/compare.py
+++ b/rdflib/compare.py
@@ -469,8 +469,11 @@ class _TripleCanonicalizer(object):
 def to_isomorphic(graph):
     if isinstance(graph, IsomorphicGraph):
         return graph
-    return IsomorphicGraph(store=graph.store)
-
+    result = IsomorphicGraph()
+    if hasattr(graph, "identifier"):
+        result = IsomorphicGraph(identifier=graph.identifier)
+    result += graph
+    return result
 
 def isomorphic(graph1, graph2):
     """Compare graph for equality.
diff --git a/test/test_canonicalization.py b/test/test_canonicalization.py
index d1e38d1a..99bdb909 100644
--- a/test/test_canonicalization.py
+++ b/test/test_canonicalization.py
@@ -1,5 +1,6 @@
-from rdflib import Graph, RDF, BNode, URIRef
+from rdflib import Graph, RDF, BNode, URIRef, Namespace, ConjunctiveGraph, Literal
 from rdflib.compare import to_isomorphic, to_canonical_graph
+from rdflib.plugins.memory import IOMemory
 from six import text_type
 from io import StringIO
 
@@ -251,3 +252,36 @@ def test_issue494_collapsing_bnodes():
         'canonicalization changed number of statements'
     assert g_node_degs == cg_node_degs, \
         'canonicalization changed node degrees'
+
+def test_issue682_signing_named_graphs():
+    ns = Namespace("http://love.com#")
+
+    mary = BNode()
+    john = URIRef("http://love.com/lovers/john#")
+
+    cmary=URIRef("http://love.com/lovers/mary#")
+    cjohn=URIRef("http://love.com/lovers/john#")
+
+    store = IOMemory()
+
+    g = ConjunctiveGraph(store=store)
+    g.bind("love",ns)
+
+    gmary = Graph(store=store, identifier=cmary)
+
+    gmary.add((mary, ns['hasName'], Literal("Mary")))
+    gmary.add((mary, ns['loves'], john))
+
+    gjohn = Graph(store=store, identifier=cjohn)
+    gjohn.add((john, ns['hasName'], Literal("John")))
+
+    ig = to_isomorphic(g)
+    igmary = to_isomorphic(gmary)
+
+    print len(igmary), len(mary)
+    assert len(igmary) == len(gmary)
+    print len(ig), len(g)
+    assert len(ig) == len(g)
+    assert len(igmary) < len(ig)
+    print ig.graph_digest(), igmary.graph_digest()
+    assert ig.graph_digest() != igmary.graph_digest()