Fix exception when additionalProperties is boolean

jsonschema draft 4 allows additionalProperties to be true and false, in
addition to containing a subschema.

Related to: #30

jsonmerge/strategies.py

@@ -262,7 +262,8 @@ def merge(self, walk, base, head, schema, meta, objclass_menu=None, objClass='_d
 
                 if subschema.is_undef():
                     p = schema.get('additionalProperties')
-                    if not p.is_undef():
+                    # additionalProperties can be boolean in draft 4
+                    if not p.is_undef() and walk.is_type(p, "object"):
                         subschema = p
 
             base[k] = walk.descend(subschema, base.get(k), v, meta)
@@ -281,8 +282,9 @@ def descend_keyword(keyword):
         descend_keyword("properties")
         descend_keyword("patternProperties")
 
+       # additionalProperties can be boolean in draft 4
         p = schema.get("additionalProperties")
-        if not p.is_undef():
+        if not p.is_undef() and walk.is_type(p, "object"):
             schema2["additionalProperties"] = walk.descend(p, meta)
 
         return schema2

tests/test_jsonmerge.py

@@ -338,6 +338,17 @@ def test_merge_append_additional(self):
 
         self.assertEqual(base, {'a': ["a", "b"], 'b': 'c'})
 
+    def test_merge_additional_bool(self):
+
+        schema = {'additionalProperties': True}
+
+        base = {}
+        head = {'a': 'a'}
+
+        base = jsonmerge.merge(base, head, schema)
+
+        self.assertEqual(base, {'a': 'a'})
+
     def test_example(self):
 
         head1 = {
@@ -1857,6 +1868,18 @@ def test_merge_append_additional(self):
 
         self.assertEqual(schema2, expected)
 
+    def test_merge_additional_bool(self):
+
+        schema = {'additionalProperties': True}
+
+        base = {}
+        head = {'a': 'a'}
+
+        merger = jsonmerge.Merger(schema)
+        schema2 = merger.get_schema()
+
+        self.assertEqual(schema2, schema)
+
     def test_oneof(self):
 
         schema = {