Source code for falcon.routing.util

# Copyright 2013 by Rackspace Hosting, Inc.
# 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
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.

"""Routing utilities."""

import re

import six

from falcon import HTTP_METHODS, responders

# NOTE(kgriffs): Published method; take care to avoid breaking changes.
[docs]def compile_uri_template(template): """Compile the given URI template string into a pattern matcher. This function can be used to construct custom routing engines that iterate through a list of possible routes, attempting to match an incoming request against each route's compiled regular expression. Each field is converted to a named group, so that when a match is found, the fields can be easily extracted using :py:meth:`re.MatchObject.groupdict`. This function does not support the more flexible templating syntax used in the default router. Only simple paths with bracketed field expressions are recognized. For example:: / /books /books/{isbn} /books/{isbn}/characters /books/{isbn}/characters/{name} Also, note that if the template contains a trailing slash character, it will be stripped in order to normalize the routing logic. Args: template(str): The template to compile. Note that field names are restricted to ASCII a-z, A-Z, and the underscore character. Returns: tuple: (template_field_names, template_regex) """ if not isinstance(template, six.string_types): raise TypeError('uri_template is not a string') if not template.startswith('/'): raise ValueError("uri_template must start with '/'") if '//' in template: raise ValueError("uri_template may not contain '//'") if template != '/' and template.endswith('/'): template = template[:-1] # template names should be able to start with A-Za-z # but also contain 0-9_ in the remaining portion expression_pattern = r'{([a-zA-Z]\w*)}' # Get a list of field names fields = set(re.findall(expression_pattern, template)) # Convert Level 1 var patterns to equivalent named regex groups escaped = re.sub(r'[\.\(\)\[\]\?\*\+\^\|]', r'\\\g<0>', template) pattern = re.sub(expression_pattern, r'(?P<\1>[^/]+)', escaped) pattern = r'\A' + pattern + r'\Z' return fields, re.compile(pattern, re.IGNORECASE)
[docs]def create_http_method_map(resource): """Maps HTTP methods (e.g., 'GET', 'POST') to methods of a resource object. Args: resource: An object with *responder* methods, following the naming convention *on_\**, that correspond to each method the resource supports. For example, if a resource supports GET and POST, it should define ``on_get(self, req, resp)`` and ``on_post(self, req, resp)``. Returns: dict: A mapping of HTTP methods to responders. """ method_map = {} for method in HTTP_METHODS: try: responder = getattr(resource, 'on_' + method.lower()) except AttributeError: # resource does not implement this method pass else: # Usually expect a method, but any callable will do if callable(responder): method_map[method] = responder # Attach a resource for unsupported HTTP methods allowed_methods = sorted(list(method_map.keys())) if 'OPTIONS' not in method_map: # OPTIONS itself is intentionally excluded from the Allow header opt_responder = responders.create_default_options(allowed_methods) method_map['OPTIONS'] = opt_responder allowed_methods.append('OPTIONS') na_responder = responders.create_method_not_allowed(allowed_methods) for method in HTTP_METHODS: if method not in allowed_methods: method_map[method] = na_responder return method_map