Correct way to use a custom 404 view

[Benjamin Sims]

Hi,

I'm trying to generate a custom 404 view for my application. I've read:

https://pylonsproject.org/projects/pyramid/dev/narr/hooks.html#changing-the-notfound-view

However, I want to be able to have the 404 use a Chameleon template with macros and so forth in order to fit in with the overall look and feel.

I have:

config.add_view(notfound_view, renderer = 'templates/view_not_found.pt', context=HTTPNotFound)

in the __init__, and:

def notfound_view(request):
    master = get_renderer('templates/macros_template.pt').implementation()
    return dict(master = master)

as the relevant view. However, while it will correctly give me the 404 page I want to see, the HTTP header will be a 200 OK.

I'm aware that I can do:

def notfound_view(request):
    return HTTPNotFound()

however I then of course do not see my templated view.

Could somebody please expand on the documentation example and tell me what calls I need to achieve this?

Thanks,
Ben

[Chris McDonough]

On Tue, 2011-09-13 at 15:05 +0100, Benjamin Sims wrote:
> Hi,
>
> I'm trying to generate a custom 404 view for my application. I've
> read:
>
> https://pylonsproject.org/projects/pyramid/dev/narr/hooks.html#changing-the-notfound-view
>
> However, I want to be able to have the 404 use a Chameleon template
> with macros and so forth in order to fit in with the overall look and
> feel.
>
> I have:
>
> config.add_view(notfound_view, renderer =
> 'templates/view_not_found.pt', context=HTTPNotFound)
>
> in the __init__, and:
>
> def notfound_view(request):
> master =
> get_renderer('templates/macros_template.pt').implementation()
> return dict(master = master)

def notfound_view(request):
request.response.status_int = 404
master get_renderer('templates/macros_template.pt').implementation()
return dict(master = master)

It's slightly different in 1.0, but the above works in 1.1 and 1.2.

- C

[Benjamin Sims]

Thanks Chris, that works great.

Sorry for the follow on question, but is there a similar way to handle Python errors/500?

I have set up pyramid_exclog to send any errors to me by email. I also have the following lines in my ini:


[pipeline:main]
pipeline =
    tm
    myapp

[filter:weberror]
use = egg:WebError#error_catcher
debug = false

I now get a correct 500 error and a message saying 'Internal Server Error'. However, I would like to customise that error so that it works in a similar way to the 404.

I tried adding this to the __init__:

from pyramid.httpexceptions import HTTPInternalServerError
from myapp.system import internal_error_view
    config.add_view(internal_error_view, renderer = 'templates/internal_error.pt',
            context=HTTPInternalServerError)

However, this does not work (which as I understand it makes sense, since the above indicates that the error has already gone out to paster).

Is there a catch-all way to catch the errors in Pyramid and use a fancy error page?

Thanks,
Ben

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[Michael Merickel]

The way to think about this is that Pyramid is at the end of a WSGI pipeline. It supports a way for catching and handling any exceptions that occur within Pyramid itself via exception views. You have seen one exception view already via the HTTPNotFound exception. You may add an exception view for anything raised within Pyramid, including HTTPForbidden, HTTPInternalServerError or even *Exception*. An exception view is invoked if an exception of that type is *raised*. Thus for your HTTPInternalServerError exception view to be invoked you'd need to "raise HTTPInternalServerError" somewhere in your code. Obviously the general way to add a view for all exceptions is to add a view for Exception, which uses your internal_error template and sets the response's status to 500. You can then further add more specific instances of Exception, like HTTPNotFound if you wanted a different error template (or status code) for that exception.

Note that exception views only work for exceptions, if you *return* HTTPNotFound, the exception view will not be invoked and the returned value will be expected to be a conforming Response object (which it happens to be).

Now, if an exception is not handled by Pyramid because you didn't add a view for it, then it will simply propagate up the WSGI stack until something else handled it. WebError is one such option. If left unhandled, the WSGI server will catch it and return a default 500 page (which is what you're seeing).

Your INI setup is actually incorrect, because you didn't actually add the filter to the pipeline. Configuring a filter is only one step, you also must add it:

[pipeline:main]

pipeline =

  weberror

  tm

  myapp

--

Michael

[Benjamin Sims]

Thanks Michael, adding a view for the Exception context worked perfectly. So, I did this in __init__.py:

from myapp.system import error_view
config.add_view(error_view, renderer = 'templates/error_template.pt', context=Exception)

Ben

--