Reject invalid patch document containers

jsonpatch.py

@@ -518,11 +518,18 @@ def __init__(self, patch, pointer_cls=JsonPointer):
         self.patch = patch
         self.pointer_cls = pointer_cls
 
+        if isinstance(patch, (str, bytes, Mapping)):
+            raise InvalidJsonPatch("Document is expected to be sequence of operations")
+        try:
+            patch_iter = iter(patch)
+        except TypeError:
+            raise InvalidJsonPatch("Document is expected to be sequence of operations")
+
         # Verify that the structure of the patch document
         # is correct by retrieving each patch element.
         # Much of the validation is done in the initializer
         # though some is delayed until the patch is applied.
-        for op in self.patch:
+        for op in patch_iter:
             # We're only checking for strings in the following check
             # for two reasons:
             #

property_tests.py

@@ -324,6 +324,15 @@ def test_result_shares_nothing_with_dst(self, docs):
 
 class ApplyPatchProperties(unittest.TestCase):
 
+    @given(st.one_of(json_scalars, st.dictionaries(json_keys, json_docs)))
+    @example(patch={})
+    @example(patch='')
+    def test_non_array_patch_documents_are_rejected(self, patch):
+        with self.assertRaises(jsonpatch.InvalidJsonPatch):
+            jsonpatch.JsonPatch(patch)
+        with self.assertRaises(jsonpatch.InvalidJsonPatch):
+            jsonpatch.JsonPatch.from_string(json.dumps(patch))
+
     @given(docs_with_patches())
     def test_does_not_modify_document(self, case):
         doc, patch = case

tests.py

@@ -1533,6 +1533,35 @@ def test_copy_from_pointer(self):
 
 class JsonPatchCreationTest(unittest.TestCase):
 
+    def test_creation_rejects_non_sequence_documents(self):
+        for patch in ({}, {'op': 'add', 'path': '/a', 'value': 1},
+                      MappingProxyType({}), '', b'', None, True, False,
+                      0, 1, 1.5):
+            with self.subTest(patch=patch):
+                with self.assertRaises(jsonpatch.InvalidJsonPatch):
+                    jsonpatch.JsonPatch(patch)
+
+    def test_serialized_patch_rejects_non_array_documents(self):
+        for patch in ({}, {'op': 'add', 'path': '/a', 'value': 1},
+                      '', 'text', None, True, False, 0, 1, 1.5):
+            for serialized in (json.dumps(patch), json.dumps(patch).encode()):
+                with self.subTest(patch=serialized):
+                    with self.assertRaises(jsonpatch.InvalidJsonPatch):
+                        jsonpatch.JsonPatch.from_string(serialized)
+                    doc = {'a': 'unchanged'}
+                    with self.assertRaises(jsonpatch.InvalidJsonPatch):
+                        jsonpatch.apply_patch(doc, serialized, in_place=True)
+                    self.assertEqual(doc, {'a': 'unchanged'})
+
+    def test_creation_preserves_operation_sequences(self):
+        for operations in ([], (),
+                           [{'op': 'add', 'path': '/a', 'value': 1}],
+                           ({'op': 'add', 'path': '/a', 'value': 1},)):
+            with self.subTest(operations=operations):
+                patch = jsonpatch.JsonPatch(operations)
+                self.assertIs(patch.patch, operations)
+                self.assertEqual(patch.apply({}), {'a': 1} if operations else {})
+
     def test_creation_fails_with_invalid_patch(self):
         invalid_patches = [
             {             'path': '/foo', 'value': 'bar'},