Merge pull request #2986 from taion/do-not-handle-routing-exception

Do not handle RoutingExceptions with app error handlers

CHANGES.rst

@@ -19,11 +19,16 @@ Unreleased
     Python version. (`#2825`_)
 -   :func:`send_file` handles an ``attachment_filename`` that is a
     native Python 2 string (bytes) with UTF-8 coded bytes. (`#2933`_)
+-   A catch-all error handler registered for ``HTTPException`` will not
+    handle ``RoutingExcpetion``, which is used internally during
+    routing. This fixes the unexpected behavior that had been introduced
+    in 1.0. (`#2986`_)
 
 .. _#2766: https://github.com/pallets/flask/issues/2766
 .. _#2765: https://github.com/pallets/flask/pull/2765
 .. _#2825: https://github.com/pallets/flask/pull/2825
 .. _#2933: https://github.com/pallets/flask/issues/2933
+.. _#2986: https://github.com/pallets/flask/pull/2986
 
 
 Version 1.0.2

flask/app.py

@@ -20,7 +20,8 @@ from threading import Lock
 from werkzeug.datastructures import Headers, ImmutableDict
 from werkzeug.exceptions import BadRequest, BadRequestKeyError, HTTPException, \
     InternalServerError, MethodNotAllowed, default_exceptions
-from werkzeug.routing import BuildError, Map, RequestRedirect, Rule
+from werkzeug.routing import BuildError, Map, RequestRedirect, \
+    RoutingException, Rule
 
 from . import cli, json
 from ._compat import integer_types, reraise, string_types, text_type
@@ -1631,6 +1632,16 @@ class Flask(_PackageBoundObject):
         registered error handlers and fall back to returning the
         exception as response.
 
+        .. versionchanged:: 1.0.3
+            ``RoutingException``, used internally for actions such as
+             slash redirects during routing, is not passed to error
+             handlers.
+
+        .. versionchanged:: 1.0
+            Exceptions are looked up by code *and* by MRO, so
+            ``HTTPExcpetion`` subclasses can be handled with a catch-all
+            handler for the base ``HTTPException``.
+
         .. versionadded:: 0.3
         """
         # Proxy exceptions don't have error codes.  We want to always return
@@ -1638,6 +1649,12 @@ class Flask(_PackageBoundObject):
         if e.code is None:
             return e
 
+        # RoutingExceptions are used internally to trigger routing
+        # actions, such as slash redirects raising RequestRedirect. They
+        # are not raised or handled in user code.
+        if isinstance(e, RoutingException):
+            return e
+
         handler = self._find_error_handler(e)
         if handler is None:
             return e

tests/test_user_error_handler.py

@@ -184,6 +184,10 @@ def test_default_error_handler():
     def forbidden():
         raise Forbidden()
 
+    @app.route("/slash/")
+    def slash():
+        return "slash"
+
     app.register_blueprint(bp, url_prefix='/bp')
 
     c = app.test_client()
@@ -191,5 +195,5 @@ def test_default_error_handler():
     assert c.get('/bp/forbidden').data == b'bp-forbidden'
     assert c.get('/undefined').data == b'default'
     assert c.get('/forbidden').data == b'forbidden'
-
-
+    # Don't handle RequestRedirect raised when adding slash.
+    assert c.get("/slash", follow_redirects=True).data == b"slash"