Allow graphql schema export to use a canonical representation

docs/introspection.rst

@@ -11,7 +11,7 @@ data to ``schema.json`` that is compatible with babel-relay-plugin.
 Usage
 -----
 
-Include ``graphene_django`` to ``INSTALLED_APPS`` in you project
+Include ``graphene_django`` to ``INSTALLED_APPS`` in your project
 settings:
 
 .. code:: python
@@ -29,6 +29,8 @@ It dumps your full introspection schema to ``schema.json`` inside your
 project root directory. Point ``babel-relay-plugin`` to this file and
 you're ready to use Relay with Graphene GraphQL implementation.
 
+The schema file is sorted to create a reproducible canonical representation.
+
 Advanced Usage
 --------------
 

graphene_django/management/commands/graphql_schema.py

@@ -39,7 +39,7 @@ class Command(CommandArguments):
 
     def save_file(self, out, schema_dict, indent):
         with open(out, "w") as outfile:
-            json.dump(schema_dict, outfile, indent=indent)
+            json.dump(schema_dict, outfile, indent=indent, sort_keys=True)
 
     def handle(self, *args, **options):
         options_schema = options.get("schema")
@@ -65,7 +65,7 @@ class Command(CommandArguments):
         indent = options.get("indent")
         schema_dict = {"data": schema.introspect()}
         if out == '-':
-            self.stdout.write(json.dumps(schema_dict, indent=indent))
+            self.stdout.write(json.dumps(schema_dict, indent=indent, sort_keys=True))
         else:
             self.save_file(out, schema_dict, indent)
 

graphene_django/tests/test_command.py

@@ -1,5 +1,5 @@
 from django.core import management
-from mock import patch
+from mock import patch, mock_open
 from six import StringIO
 
 
@@ -8,3 +8,15 @@ def test_generate_file_on_call_graphql_schema(savefile_mock, settings):
     out = StringIO()
     management.call_command("graphql_schema", schema="", stdout=out)
     assert "Successfully dumped GraphQL schema to schema.json" in out.getvalue()
+
+
+@patch('json.dump')
+def test_files_are_sorted(dump_mock):
+    open_mock = mock_open()
+    with patch('graphene_django.management.commands.graphql_schema.open', open_mock):
+        management.call_command('graphql_schema', schema='')
+
+    open_mock.assert_called_once()
+
+    dump_mock.assert_called_once()
+    assert dump_mock.call_args[1]["sort_keys"], "json.mock() should be used to sort the output"