Fix nesteddict2yaml not to fumble empty dict values

aiohttp_swagger/helpers/builders.py

@@ -94,7 +94,7 @@ def generate_doc_from_each_end_point(
     def nesteddict2yaml(d, indent=10, result=""):
         for key, value in d.items():
             result += " " * indent + str(key) + ':'
-            if isinstance(value, dict):
+            if isinstance(value, dict) and value:
                 result = nesteddict2yaml(value, indent + 2, result + "\n")
             elif isinstance(value, str):
                 result += " \"" + str(value) + "\"\n"

tests/data/example_data_definitions.json

@@ -37,6 +37,11 @@
         "type": "string",
         "description": "User's permission parameter",
         "default": "some_perm"
+      },
+      "permission_param_3": {
+        "type": "object",
+        "description": "User's permission parameter",
+        "default": {}
       }
     },
     "required": [

tests/test_openapi.py

@@ -309,6 +309,7 @@ async def test_data_defs(aiohttp_client, loop):
     assert 'User' in result['components']['schemas']
     assert 'Permission' in result['components']['schemas']
     assert result['components']['schemas']['User']['properties']['permissions']['items']['$ref'] is not None
+    assert result['components']['schemas']['Permission']['properties']['permission_param_3']['default'] is not None
 
 
 async def test_sub_app(aiohttp_client, loop):

tests/test_swagger.py

@@ -356,6 +356,7 @@ async def test_data_defs(aiohttp_client, loop):
     assert 'User' in result['definitions']
     assert 'Permission' in result['definitions']
     assert result['definitions']['User']['properties']['permissions']['items']['$ref'] is not None
+    assert result['definitions']['Permission']['properties']['permission_param_3']['default'] is not None
 
 
 async def test_sub_app(aiohttp_client, loop):