Fixed __primaryvalue__ for composite keys

docs/ogm/index.rst

@@ -56,6 +56,9 @@ Each instance may contain attributes that represent labels, nodes or related obj
       The primary node label used for Cypher `MATCH` and `MERGE`
       operations. By default the name of the class is used.
 
+      This value can also be a tuple, in which case a composite primary
+      label is implied.
+
    .. attribute:: __primarykey__
 
       The primary property key used for Cypher `MATCH` and `MERGE`
@@ -65,11 +68,15 @@ Each instance may contain attributes that represent labels, nodes or related obj
       :meth:`.Graph.create` and :meth:`.Graph.merge` on :class:`.Model`
       instances.
 
+      This value can also be a tuple, in which case a composite primary
+      key is implied.
+
    .. attribute:: __primaryvalue__
 
       The value of the property identified by :attr:`.__primarykey__`.
       If the key is ``"__id__"`` then this value returns the internal
-      node ID.
+      node ID. If the primary key is a tuple, then a corresponding
+      tuple of property values is returned.
 
    .. attribute:: __node__
 

py2neo/ogm/__init__.py

@@ -503,6 +503,8 @@ def __primaryvalue__(self):
         primary_key = self.__primarykey__
         if primary_key == "__id__":
             return node.identity
+        elif isinstance(primary_key, tuple):
+            return tuple(node[key] for key in primary_key)
         else:
             return node[primary_key]
 

test/integration/ogm/test_ogm.py

@@ -168,3 +168,13 @@ def test_push(repo, thing):
     repo.push(thing)
     assert thing.__node__.graph is repo.graph
     assert thing.__node__.identity is not None
+
+
+def test_primary_value_with_single_key(repo):
+    person = UniquePerson()
+    assert person.__primaryvalue__ == "Alice"
+
+
+def test_primary_value_with_composite_key(repo):
+    person = UniqueFullyNamedPerson()
+    assert person.__primaryvalue__ == ("Alice", "Smith")