Add a colander body validator ?

[leplatrem]

With the new validation API in #376, it is now possible to have schemas that validate things accross different parts of the request (e.g. querystring/headers/body). This is very convenient and powerful but can be tedious if you only need to validate body payloads because you have to define schemas like this:

    from cornice.validators import colander_validator

    class Payload(colander.MappingSchema):
        username = colander.SchemaNode(colander.String())

    class SignupSchema(colander.MappingSchema):
        body = Payload()

    signup = cornice.Service()

    @signup.get(schema=SignupSchema, validators=(colander_validator,))
    def signup_get(request):
        username = request.validated['body']['username']
        return {'success': True}

We could have a colander_body_validator that validates the body only, which would prevent having to define a upper level schema:

    from cornice.validators import colander_body_validator

    class SignupSchema(colander.MappingSchema):
        username = colander.SchemaNode(colander.String())

    signup = cornice.Service()

    @signup.get(schema=SignupSchema, validators=(colander_body_validator,))
    def signup_get(request):
        username = request.validated['username']  # no ['body']
        return {'success': True}

The code is short and would look like this:

diff --git a/cornice/validators/_colander.py b/cornice/validators/_colander.py
index 5136dca..ba83424 100644
--- a/cornice/validators/_colander.py
+++ b/cornice/validators/_colander.py
@@ -1,12 +1,28 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this file,
 # You can obtain one at http://mozilla.org/MPL/2.0/.
-from colander import Invalid
+import colander
+
+from cornice.validators import extract_cstruct
+
+
+def _body_deserializer(request):
+    request_data = extract_cstruct(request)
+    return request_data['body']
+
+
+def body_validator(request, **kwargs):
+    schema = kwargs.get('schema')
+    if schema is not None:
+        request_schema = colander.MappingSchema()
+        request_schema.add('body', schema())
+        kwargs['schema'] = request_schema
+        kwargs['deserializer'] = _body_deserializer
+    return validator(request, **kwargs)


 def validator(request, deserializer=None, **kw):
     if deserializer is None:
-        from cornice.validators import extract_cstruct
         deserializer = extract_cstruct

     schema = kw.get('schema')
@@ -19,7 +35,7 @@ def validator(request, deserializer=None, **kw):
     try:
         deserialized = schema.deserialize(cstruct)
         request.validated.update(deserialized)
-    except Invalid as e:
+    except colander.Invalid as e:
         translate = request.localizer.translate
         error_dict = e.asdict(translate=translate)
         for name, msg in error_dict.items():

[tarekziade]

+1