Optimization: minimize instantiations of Schema in use_args

If a dict is passed as the argmap, we only need to
generate and instantiate a Schema once

Also, add a test for aiohttpparser's use_args with schema factory

Author: sloria

tests/test_aiohttp/test_aiohttpparser.py

@@ -124,6 +124,26 @@ def echo_use_args(request, args):
     assert res.json == {'name': 'Joe'}
 
 
+def test_use_args_with_callable(app, client):
+
+    class MySchema(Schema):
+        foo = fields.Field(missing=42)
+
+    def make_schema(req):
+        return MySchema(context={'request': req})
+
+    @asyncio.coroutine
+    @use_args(make_schema)
+    def echo_use_args(request, args):
+        return jsonify(args)
+
+    app.router.add_route('GET', '/use_args', echo_use_args)
+
+    res = client.get('/use_args')
+    assert res.status_code == 200
+    assert res.json == {'foo': 42}
+
+
 def test_use_kwargs_on_method(app, client):
     class Handler:
 

webargs/async.py

@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 """Asynchronous request parser. Compatible with Python>=3.4."""
 import asyncio
+import collections
 import inspect
 import functools
 
@@ -62,6 +63,10 @@ def use_args(self, argmap, req=None, locations=None, as_kwargs=False, validate=N
         """
         locations = locations or self.locations
         request_obj = req
+        # Optimization: If argmap is passed as a dictionary, we only need
+        # to generate a Schema once
+        if isinstance(argmap, collections.Mapping):
+            argmap = core.argmap2schema(argmap)()
 
         def decorator(func):
             req_ = request_obj

webargs/core.py

@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
+import collections
 import functools
 import inspect
 import logging
@@ -282,8 +283,9 @@ def _get_schema(self, argmap, req):
     def parse(self, argmap, req=None, locations=None, validate=None, force_all=False):
         """Main request parsing method.
 
-        :param dict argmap: Either a `marshmallow.Schema` or a `dict`
-            of argname -> `marshmallow.fields.Field` pairs.
+        :param argmap: Either a `marshmallow.Schema`, `dict`
+            of argname -> `marshmallow.fields.Field` pairs, or a callable that returns
+            a `marshmallow.Schema` instance.
         :param req: The request object to parse.
         :param tuple locations: Where on the request to search for values.
             Can include one or more of ``('json', 'querystring', 'form',
@@ -359,6 +361,10 @@ def greet(args):
         """
         locations = locations or self.locations
         request_obj = req
+        # Optimization: If argmap is passed as a dictionary, we only need
+        # to generate a Schema once
+        if isinstance(argmap, collections.Mapping):
+            argmap = argmap2schema(argmap)()
 
         def decorator(func):
             req_ = request_obj