Added special handling for mapped paths with trailing slashes

src/milla/dispatch/routing.py

@@ -11,12 +11,6 @@
 # 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.
-from milla.dispatch import UnresolvedPath
-import functools
-import re
-import sys
-import urllib
-import urlparse
 '''URL router
 
 :Created: Mar 13, 2011
@@ -25,6 +19,13 @@ import urlparse
 :Updater: $Author$
 '''
 
+from milla.dispatch import UnresolvedPath
+import functools
+import milla
+import re
+import sys
+import urllib
+import urlparse
 
 class Router(object):
     '''A dispatcher that maps arbitrary paths to controller callables
@@ -34,14 +35,43 @@ class Router(object):
         router = Router()
         router.add_route('/foo/{bar}/{baz:\d+}', some_func)
         app = milla.Application(dispatcher=router)
+    
+    In many cases, paths with trailing slashes need special handling.
+    The ``Router`` has two ways of dealing with requests that should
+    have a trailing slash but do not. The default is to send the client
+    an HTTP 301 Moved Permanently response, and the other is to
+    simply treat the request as if it had the necessary trailing slash.
+    A third option is to disable special handling entirely and simply
+    return HTTP 404 Not Found for requests with missing trailing
+    slashes. To change the behavior, pass a different value to the
+    constructor's ``trailing_slash`` keyword.
+    
+    Redirect the client to the proper path (the default)::
+    
+        router = Router(trailing_slash=Router.REDIRECT)
+        router.add_route('/my_collection/', some_func)
+    
+    Pretend the request had a trailing slash, even if it didn't::
+    
+        router = Router(trailing_slash=Router.SILENT)
+        router.add_route('/my_collection/', some_func)
+    
+    Do nothing, let the client get a 404 error::
+    
+       router = Router(trailing_slash=None)
+       router.add_route('/my_collection/', some_func)
     '''
 
+    class REDIRECT(object): pass
+    class SILENT(object): pass
+    
     #: Compiled regular expression for variable segments
     template_re = re.compile(r'\{(\w+)(?::([^}]+))?\}')
 
-    def __init__(self):
+    def __init__(self, trailing_slash=REDIRECT):
         self.routes = []
         self._cache = {}
+        self.trailing_slash=trailing_slash
 
     def resolve(self, path_info):
         '''Find a controller for a given path
@@ -56,9 +86,8 @@ class Router(object):
         matches the given path. Variable segments are added as keywords
         to the controller function.
         '''
-        try:
-            return self._cache[path_info]
-        except KeyError:
+
+        def lookup(path_info):
             for regex, controller, vars in self.routes:
                 match = regex.match(path_info)
                 if match:
@@ -71,6 +100,27 @@ class Router(object):
                         func.__doc__ = controller.__doc__
                     self._cache[path_info] = func
                     return func
+
+        try:
+            return self._cache[path_info]
+        except KeyError:
+            func = lookup(path_info)
+            if func:
+                return func
+            elif self.trailing_slash and not path_info.endswith('/'):
+                # Try to resolve the path with a trailing slash
+                new_path_info = path_info + '/'
+                func = lookup(new_path_info)
+                if func and self.trailing_slash is Router.REDIRECT:
+                    # Return a dummy function that just raises
+                    # HTTPMovedPermanently to redirect the client to
+                    # the canonical URL
+                    def redir(*args, **kwargs):
+                        raise milla.HTTPMovedPermanently(location=new_path_info)
+                    return redir
+                elif func and self.trailing_slash is Router.SILENT:
+                    # Return the function found at the alternate path
+                    return func
         raise UnresolvedPath
 
     def _compile_template(self, template):