ValidationMixin for Tornado

ValidationMixin

#!/usr/bin/env python
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.

"""A mixin for validating form submissions in Tornado"""

import re
import logging

class ValidationMixin:
    
    MSG_DEFAULT = u"is not valid"
    MSG_REQUIRED = u"is required"
    MSG_MUST_MATCH = u" doesn't match"
    
    ALPHA = r"^\D+$"
    NUMERIC = r"^\d+$"
    EMAIL = r"^[a-zA-Z0-9._%-+]+\@[a-zA-Z0-9._%-]+\.[a-zA-Z]{2,}$"
    USERNAME = r"^[a-z0-9._]{3,}$"
    
    def _help(self, specified, name, type):
        if specified is not None:
            self.errors[name] = specified
        else:
            self.errors[name] = name + " " + type
    
    def valid(self, arg_name, validator = None, help = None, name = None, required = True):
        """
        Tornado mixin for validating POST arguments
        Alternative to self.get_argument, but validates first
        Returns the argument after validating it
        Any validation errors will be in self.errors as a dict in the form:
            { field_name: help_message }
        
        Parameters:
        @arg_name: name of the argument to check
        @required: validate for filled-in first (default is True)
        @help: help message to display if argument doesn't validate
        @name: argument title, default is replacing _ with " " and capitalizing the arg name.
               this is how the field name appears in generated error messages
        @validator: can be either:
            - not specified
            - a validation function returning True or False
            - a string containing another argument name: the two must match
            - a string containing a regular expression: must match (case-insensitive)
            - a python type (int, float, bool)
        """
        value = self.get_argument(arg_name, None)
        value2 = self.get_argument(validator, None)
        
        if not hasattr(self, "errors"):
            self.errors = {}
        if not required and not validator:
            # nothing to validate
            return value
        if arg_name in self.errors:
            return value # already validated
        if not name:
            name = arg_name.replace("_", " ").capitalize()
        # not filled in ?
        if required and (value is None or len(value) == 0):
            self._help(help, name, ValidationMixin.MSG_REQUIRED)
        # doesn't match custom function ?
        elif type(validator) == type(self.valid):
            if not validator(value):
                self._help(help, name, ValidationMixin.MSG_DEFAULT)
        # doesn't match type ?
        elif type(validator) == type:
            if type == int:
                try:
                    value = int(value)
                except ValueError:
                    self._help(help, name, ValidationMixin.MSG_DEFAULT)
            elif type == float:
                try:
                    value = float(value)
                except ValueError:
                    self._help(help, name, ValidationMixin.MSG_DEFAULT)
            elif type == bool:
                if value.lower() not in [ "1", "true", "yes", "on" ]:
                    self._help(help, name, ValidationMixin.MSG_DEFAULT)
        # doesn't match another argument ?
        elif value2 is not None:
            if value != value2:
                self._help(help, name, ValidationMixin.MSG_MUST_MATCH)
        # doesn't match regex format ?
        elif type(validator) == str:
            if re.match(validator, value, re.IGNORECASE) is None:
                self._help(help, name, ValidationMixin.MSG_DEFAULT)
        return value