Add a hook to the error middleware to ignore (re-raise) exceptions in env[paste.expected_exceptions]; also made httpexceptions put this in. This way if httpexceptions wraps error middleware, it'll still work

2 files changed, 15 insertions, 1 deletions

diff --git a/paste/exceptions/errormiddleware.py b/paste/exceptions/errormiddleware.py
index 781efe5..cc4bd57 100644
--- a/paste/exceptions/errormiddleware.py
+++ b/paste/exceptions/errormiddleware.py
@@ -57,6 +57,13 @@ class ErrorMiddleware(object):
 
     ``error_message``:
         When debug mode is off, the error message to show to users.
+
+    This also looks for a special key ``'paste.expected_exceptions``,
+    which should be a list of exception classes.  When an exception is
+    raised, if it is found in this list then it will be re-raised
+    instead of being caught.  This should generally be set by
+    middleware that may (but probably shouldn't be) installed above
+    this middleware, and wants to get certain exceptions.
     """
 
     def __init__(self, application, global_conf=None,
@@ -118,6 +125,9 @@ class ErrorMiddleware(object):
             return self.catching_iter(app_iter, environ)
         except:
             exc_info = sys.exc_info()
+            for expected in environ.get('paste.expected_exceptions', []):
+                if issubclass(exc_info[0], expected):
+                    raise
             if not started:
                 start_response('500 Internal Server Error',
                                [('content-type', 'text/html')],
diff --git a/paste/httpexceptions.py b/paste/httpexceptions.py
index ce3ab79..b01be07 100644
--- a/paste/httpexceptions.py
+++ b/paste/httpexceptions.py
@@ -225,13 +225,17 @@ def middleware(application, global_conf=None):
     """
 
     def start_application(environ, start_response):
+        environ.setdefault('paste.expected_exceptions', []).append(
+            HTTPException)
         app_started = []
         def checked_start_response(status, headers, exc_info=None):
             app_started.append(None)
             return start_response(status, headers, exc_info)
         
         try:
-            return application(environ, checked_start_response)
+            v = application(environ, checked_start_response)
+            environ['paste.expected_exceptions'].remove(HTTPException)
+            return v
         except HTTPException, e:
             if environ.get('paste.debug_suppress_httpexceptions'):
                 raise