Added support for "hooks" which are like a simpler form of middleware.

pecan/hooks.py

@@ -0,0 +1,44 @@
+class PecanHook(object):
+    def before(self, state):
+        pass
+    
+    def after(self, state):
+        pass
+    
+    def on_error(self, state):
+        pass
+
+
+class TransactionHook(PecanHook):
+    def __init__(self, start, start_ro, commit, rollback, clear):
+        self.start    = start
+        self.start_ro = start_ro
+        self.commit   = commit
+        self.rollback = rollback
+        self.clear    = clear
+    
+    def is_transactional(self, state):
+        if state.request.method not in ('GET', 'HEAD'):
+            return True
+        return False
+    
+    def before(self, state):
+        state.request.error = False
+        if self.is_transactional(state):
+            state.request.transactional = True
+            self.start()
+        else:
+            state.request.transactional = False
+            self.start_ro()
+    
+    def on_error(self, state):
+        state.request.error = True
+        self.rollback()
+    
+    def after(self, state):
+        if state.request.transactional:
+            if state.request.error:
+                self.rollback()
+            else:
+                self.commit()
+        self.clear()

pecan/pecan.py

@@ -23,10 +23,11 @@ def override_template(template):
 
 
 class Pecan(object):
-    def __init__(self, root, renderers=renderers, default_renderer='genshi'):
+    def __init__(self, root, renderers=renderers, default_renderer='genshi', hooks=[]):
         self.root             = root
         self.renderers        = renderers
         self.default_renderer = default_renderer
+        self.hooks            = hooks
         self.translate        = string.maketrans(
             string.punctuation, 
             '_' * len(string.punctuation)
@@ -109,7 +110,12 @@ class Pecan(object):
             response.status = 404
             return response(environ, start_response)
         
-        # get the result from the controller
+        # handle "before" hooks
+        for hook in self.hooks:
+            hook.before(state)
+        
+        # get the result from the controller, properly handling wrap hooks
+        try:
             result = controller(**dict(state.request.str_params))
                 
             # pull the template out based upon content type
@@ -131,7 +137,16 @@ class Pecan(object):
             response = Response(result)
             if content_type:
                 response.content_type = content_type
-        
-        del state.request
+        except Exception, e:
+            # handle "error" hooks
+            for hook in self.hooks:
+                hook.on_error(state, e)
+            raise
+        else:
+            # handle "after" hooks
+            for hook in self.hooks:
+                hook.after(state)
             
             return response(environ, start_response)
+        finally:
+            del state.request