Opened 6 years ago

Closed 5 years ago

#29008 closed Bug (fixed)

When DEBUG is True, raising Http404 in a path converter's to_python method does not result in a technical response

Reported by: Antoine Humeau Owned by: Ngalim Siregar
Component: Core (URLs) Version: dev
Severity: Normal Keywords:
Cc: Herbert Fortes Triage Stage: Ready for checkin
Has patch: yes Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description

This is the response I get (plain text):

A server error occurred.  Please contact the administrator.

I understand a ValueError should be raised which tells the URL resolver "this path does not match, try next one" but Http404 is what came to my mind intuitively and the error message was not very helpful.

One could also make a point that raising a Http404 should be valid way to tell the resolver "this is indeed the right path but the current parameter value does not match anything so stop what you are doing and let the handler return the 404 page (including a helpful error message when DEBUG is True instead of the default 'Django tried these URL patterns')".

This would prove useful for example to implement a path converter that uses get_object_or_404.

Change History (12)

comment:1 by Tim Graham, 6 years ago

Triage Stage: UnreviewedAccepted

It seems that other exceptions correctly result in a technical 500 response.

comment:2 by Antoine Humeau, 6 years ago

The technical_404_response view performs a new URL resolving (cf https://github.com/django/django/blob/a8e492bc81fca829f5d270e2d57703c02e58701e/django/views/debug.py#L482) which will obviously raise a new Http404 which won't be caught as only Resolver404 is checked. That means the WSGI handler fails and the WSGI server returns the previously described default error message (indeed the error message is the default one from wsgiref.handlers.BaseHandler https://docs.python.org/3.6/library/wsgiref.html#wsgiref.handlers.BaseHandler.error_body).

The solution seems to be to catch Http404 instead of Resolver404 in technical_404_response. This will result in a technical 404 page with the Http404's message displayed and will match the behaviour of when DEBUG is False.

Last edited 6 years ago by Antoine Humeau (previous) (diff)

comment:3 by Herbert Fortes, 6 years ago

Cc: Herbert Fortes added

comment:4 by Ngalim Siregar, 5 years ago

Owner: changed from nobody to Ngalim Siregar
Status: newassigned

comment:5 by Ngalim Siregar, 5 years ago

Has patch: set

Created PR , but I am not sure how to write the tests.

I've looking about the response before and after catch Http404 instead of Resolver404, and there is no difference. Should I also change the technical_404.html for response?

Last edited 5 years ago by Ngalim Siregar (previous) (diff)

comment:6 by Claude Paroz, 5 years ago

Needs tests: set

comment:7 by Ngalim Siregar, 5 years ago

Needs tests: unset

I've added test to the patch, but not sure if it is correct.

comment:8 by Mariusz Felisiak, 5 years ago

Needs tests: set
Patch needs improvement: set

comment:9 by Ngalim Siregar, 5 years ago

Needs tests: unset
Patch needs improvement: unset

I have made the requested changes; please review again

comment:10 by Mariusz Felisiak, 5 years ago

Needs tests: set
Patch needs improvement: set
Version: 2.0master

comment:11 by Mariusz Felisiak, 5 years ago

Needs tests: unset
Patch needs improvement: unset
Triage Stage: AcceptedReady for checkin

comment:12 by Mariusz Felisiak <felisiak.mariusz@…>, 5 years ago

Resolution: fixed
Status: assignedclosed

In 503f60ff:

Fixed #29008 -- Fixed crash of 404 debug page when URL path converter raises Http404.

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