Adjust _prepare_body interface to simplify improving _serialize_data

Rename _jsonify_data to _serialize_data to make its purpose easier to
understand (this was also known as _cast_body in aiohttp_api).

In exploring how to harmonize json serialization between aiothttp and
flask, we needed to be able to adjust the mimetype from within
_serialize_data. Harmonizing the actual serialization has to wait until
backwards incompatible changes can be made, but we can keep the new
interface, as these functions were introduced in this PR (#849).

connexion/apis/abstract.py

@@ -401,7 +401,7 @@ def _prepare_body_and_status_code(cls, data, mimetype, status_code=None, extra_c
             status_code = status_code.value
 
         if data is not None:
-            body = cls._jsonify_data(data, mimetype)
+            body, mimetype = cls._serialize_data(data, mimetype)
         else:
             body = data
 
@@ -414,10 +414,11 @@ def _prepare_body_and_status_code(cls, data, mimetype, status_code=None, extra_c
                          **extra_context
                      })
 
-        return body, status_code
+        return body, status_code, mimetype
 
     @classmethod
-    def _jsonify_data(cls, data, mimetype):
+    def _serialize_data(cls, data, mimetype):
+        # TODO: Harmonize with flask_api. Currently this is the backwards compatible with aiohttp_api._cast_body.
         if not isinstance(data, bytes):
             if isinstance(mimetype, str) and is_json_mimetype(mimetype):
                 body = cls.jsonifier.dumps(data)
@@ -427,7 +428,7 @@ def _jsonify_data(cls, data, mimetype):
                 body = str(data)
         else:
             body = data
-        return body
+        return body, mimetype
 
     def json_loads(self, data):
         return self.jsonifier.loads(data)

connexion/apis/aiohttp_api.py

@@ -346,7 +346,7 @@ def _build_response(cls, data, mimetype, content_type=None, headers=None, status
         if cls._is_framework_response(data):
             raise TypeError("Cannot return web.StreamResponse in tuple. Only raw data can be returned in tuple.")
 
-        data, status_code = cls._prepare_body_and_status_code(data=data, mimetype=mimetype, status_code=status_code, extra_context=extra_context)
+        data, status_code, serialized_mimetype = cls._prepare_body_and_status_code(data=data, mimetype=mimetype, status_code=status_code, extra_context=extra_context)
 
         if isinstance(data, str):
             text = data
@@ -355,7 +355,7 @@ def _build_response(cls, data, mimetype, content_type=None, headers=None, status
             text = None
             body = data
 
-        content_type = content_type or mimetype
+        content_type = content_type or mimetype or serialized_mimetype
         return web.Response(body=body, text=text, headers=headers, status=status_code, content_type=content_type)
 
     @classmethod

connexion/apis/flask_api.py

@@ -172,10 +172,10 @@ def _build_response(cls, mimetype, content_type=None, headers=None, status_code=
         if cls._is_framework_response(data):
             return flask.current_app.make_response((data, status_code, headers))
 
-        data, status_code = cls._prepare_body_and_status_code(data=data, mimetype=mimetype, status_code=status_code, extra_context=extra_context)
+        data, status_code, serialized_mimetype = cls._prepare_body_and_status_code(data=data, mimetype=mimetype, status_code=status_code, extra_context=extra_context)
 
         kwargs = {
-            'mimetype': mimetype,
+            'mimetype': mimetype or serialized_mimetype,
             'content_type': content_type,
             'headers': headers,
             'response': data,
@@ -185,13 +185,14 @@ def _build_response(cls, mimetype, content_type=None, headers=None, status_code=
         return flask.current_app.response_class(**kwargs)  # type: flask.Response
 
     @classmethod
-    def _jsonify_data(cls, data, mimetype):
-        # TODO: to discuss: Using jsonifier for all type of data, even when mimetype is not json is strange. Why ?
+    def _serialize_data(cls, data, mimetype):
+        # TODO: harmonize flask and aiohttp serialization when mimetype=None or mimetype is not JSON
+        #       (cases where it might not make sense to jsonify the data)
         if (isinstance(mimetype, str) and is_json_mimetype(mimetype)) \
                 or not (isinstance(data, bytes) or isinstance(data, str)):
-            return cls.jsonifier.dumps(data)
+            return cls.jsonifier.dumps(data), mimetype
 
-        return data
+        return data, mimetype
 
     @classmethod
     def get_request(cls, *args, **params):