Fix awaiting of async view function.

Author: maxrimlinger

flask_parameter_validation/parameter_validation.py

@@ -3,7 +3,7 @@
 import inspect
 import re
 from inspect import signature
-from flask import request
+from flask import request, Response
 from werkzeug.datastructures import ImmutableMultiDict
 from werkzeug.exceptions import BadRequest
 from .exceptions import (InvalidParameterTypeError, MissingInputError,
@@ -40,8 +40,13 @@ def __call__(self, f):
         }
         fn_list[fsig] = fdocs
 
-        @functools.wraps(f)
-        async def nested_func(**kwargs):
+        def nested_func_helper(**kwargs):
+            """
+            Validates the inputs of a Flask route or returns an error. Returns
+            are wrapped in a dictionary with a flag to let nested_func() know 
+            if it should unpack the resulting dictionary of inputs as kwargs,
+            or just return the error message.
+            """
             # Step 1 - Get expected input details as dict
             expected_inputs = signature(f).parameters
 
@@ -54,7 +59,7 @@ async def nested_func(**kwargs):
                     try:
                         json_input = request.json
                     except BadRequest:
-                        return {"error": "Could not parse JSON."}, 400
+                        return {"error": ({"error": "Could not parse JSON."}, 400), "validated": False}
 
             # Step 3 - Extract list of parameters expected to be lists (otherwise all values are converted to lists)
             expected_list_params = []
@@ -79,18 +84,32 @@ async def nested_func(**kwargs):
                     try:
                         new_input = self.validate(expected, request_inputs)
                     except (MissingInputError, ValidationError) as e:
-                        return {"error": str(e)}, 400
+                        return {"error": ({"error": str(e)}, 400), "validated": False}
                 else:
                     try:
                         new_input = self.validate(expected, request_inputs)
                     except Exception as e:
-                        return self.custom_error_handler(e)
+                        return {"error": self.custom_error_handler(e), "validated": False}
                 validated_inputs[expected.name] = new_input
 
-            if asyncio.iscoroutinefunction(f):
-                return await f(**validated_inputs)
-            else:
-                return f(**validated_inputs)
+            return {"inputs": validated_inputs, "validated": True}
+
+        if asyncio.iscoroutinefunction(f):
+            # If the view function is async, return and await a coroutine
+            @functools.wraps(f)
+            async def nested_func(**kwargs):
+                validated_inputs = nested_func_helper(**kwargs)
+                if validated_inputs["validated"]:
+                    return await f(**validated_inputs["inputs"])
+                return validated_inputs["error"]
+        else:
+            # If the view function is not async, return a function
+            @functools.wraps(f)
+            def nested_func(**kwargs):
+                validated_inputs = nested_func_helper(**kwargs)
+                if validated_inputs["validated"]:
+                    return f(**validated_inputs["inputs"])
+                return validated_inputs["error"]
 
         nested_func.__name__ = f.__name__
         return nested_func