don't clear BadRequestKeyError args

CHANGES.rst

@@ -1,5 +1,15 @@
 .. currentmodule:: flask
 
+Version 1.0.4
+-------------
+
+Unreleased
+
+-   The key information for ``BadRequestKeyError`` is no longer cleared
+    outside debug mode, so error handlers can still access it. This
+    requires upgrading to Werkzeug 0.15.5. :issue:`3249`
+
+
 Version 1.0.3
 -------------
 

flask/__init__.py

@@ -10,7 +10,7 @@
     :license: BSD-3-Clause
 """
 
-__version__ = '1.0.3'
+__version__ = '1.0.4.dev'
 
 # utilities we import from Werkzeug and Jinja2 that are unused
 # in the module but are exported as public interface.

flask/app.py

@@ -1724,14 +1724,14 @@ class Flask(_PackageBoundObject):
 
         if isinstance(e, BadRequestKeyError):
             if self.debug or self.config["TRAP_BAD_REQUEST_ERRORS"]:
+                e.show_exception = True
+
                 # Werkzeug < 0.15 doesn't add the KeyError to the 400
                 # message, add it in manually.
-                description = e.get_description()
+                # TODO: clean up once Werkzeug >= 0.15.5 is required
-
+                if e.args[0] not in e.get_description():
-                if e.args[0] not in description:
                     e.description = "KeyError: '{}'".format(*e.args)
-            else:
+            elif not hasattr(BadRequestKeyError, "show_exception"):
-                # Werkzeug >= 0.15 does add it, remove it in production
                 e.args = ()
 
         if isinstance(e, HTTPException) and not self.trap_http_exception(e):