from urllib.parse import quote
from django.http import (
HttpResponseBadRequest, HttpResponseForbidden, HttpResponseNotFound,
HttpResponseServerError,
)
from django.template import Context, Engine, TemplateDoesNotExist, loader
from django.views.decorators.csrf import requires_csrf_token
ERROR_404_TEMPLATE_NAME = '404.html'
ERROR_403_TEMPLATE_NAME = '403.html'
ERROR_400_TEMPLATE_NAME = '400.html'
ERROR_500_TEMPLATE_NAME = '500.html'
ERROR_PAGE_TEMPLATE = """
<!doctype html>
<html lang="en">
<head>
<title>%(title)s</title>
</head>
<body>
<h1>%(title)s</h1><p>%(details)s</p>
</body>
</html>
"""
# This can be called when CsrfViewMiddleware.process_view has not run,
# therefore need @requires_csrf_token in case the template needs
# {% csrf_token %}.
@requires_csrf_token
def page_not_found(request, exception, template_name=ERROR_404_TEMPLATE_NAME):
"""
Default 404 handler.
Templates: :template:`404.html`
Context:
request_path
The path of the requested URL (e.g., '/app/pages/bad_page/'). It's
quoted to prevent a content injection attack.
exception
The message from the exception which triggered the 404 (if one was
supplied), or the exception class name
"""
exception_repr = exception.__class__.__name__
# Try to get an "interesting" exception message, if any (and not the ugly
# Resolver404 dictionary)
try:
message = exception.args[0]
except (AttributeError, IndexError):
pass
else:
if isinstance(message, str):
exception_repr = message
context = {
'request_path': quote(request.path),
'exception': exception_repr,
}
try:
template = loader.get_template(template_name)
body = template.render(context, request)
content_type = None # Django will use 'text/html'.
except TemplateDoesNotExist:
if template_name != ERROR_404_TEMPLATE_NAME:
# Reraise if it's a missing custom template.
raise
# Render template (even though there are no substitutions) to allow
# inspecting the context in tests.
template = Engine().from_string(
ERROR_PAGE_TEMPLATE % {
'title': 'Not Found',
'details': 'The requested resource was not found on this server.',
},
)
body = template.render(Context(context))
content_type = 'text/html'
return HttpResponseNotFound(body, content_type=content_type)
@requires_csrf_token
def server_error(request, template_name=ERROR_500_TEMPLATE_NAME):
"""
500 error handler.
Templates: :template:`500.html`
Context: None
"""
try:
template = loader.get_template(template_name)
except TemplateDoesNotExist:
if template_name != ERROR_500_TEMPLATE_NAME:
# Reraise if it's a missing custom template.
raise
return HttpResponseServerError(
ERROR_PAGE_TEMPLATE % {'title': 'Server Error (500)', 'details': ''},
content_type='text/html',
)
return HttpResponseServerError(template.render())
@requires_csrf_token
def bad_request(request, exception, template_name=ERROR_400_TEMPLATE_NAME):
"""
400 error handler.
Templates: :template:`400.html`
Context: None
"""
try:
template = loader.get_template(template_name)
except TemplateDoesNotExist:
if template_name != ERROR_400_TEMPLATE_NAME:
# Reraise if it's a missing custom template.
raise
return HttpResponseBadRequest(
ERROR_PAGE_TEMPLATE % {'title': 'Bad Request (400)', 'details': ''},
content_type='text/html',
)
# No exception content is passed to the template, to not disclose any sensitive information.
return HttpResponseBadRequest(template.render())
# This can be called when CsrfViewMiddleware.process_view has not run,
# therefore need @requires_csrf_token in case the template needs
# {% csrf_token %}.
@requires_csrf_token
def permission_denied(request, exception, template_name=ERROR_403_TEMPLATE_NAME):
"""
Permission denied (403) handler.
Templates: :template:`403.html`
Context: None
If the template does not exist, an Http403 response containing the text
"403 Forbidden" (as per RFC 7231) will be returned.
"""
try:
template = loader.get_template(template_name)
except TemplateDoesNotExist:
if template_name != ERROR_403_TEMPLATE_NAME:
# Reraise if it's a missing custom template.
raise
return HttpResponseForbidden(
ERROR_PAGE_TEMPLATE % {'title': '403 Forbidden', 'details': ''},
content_type='text/html',
)
return HttpResponseForbidden(
template.render(request=request, context={'exception': str(exception)})
)