Django：上下文处理器未在登录页面上运行？

Question

I have created a context processor which aims to pass a certain variable to any template that gets loaded.

This is how I have defined my context processor:

from django.conf import settings

def theme(request):
    return {'custom_theme': getattr(settings, "CUSTOM_THEME", "default")}

This is how I have included my context processor in the settings file:

TEMPLATES = [{
    'BACKEND': 'django.template.backends.django.DjangoTemplates',
    'APP_DIRS': True,
    'DIRS': [
        normpath(join(PROJECT_PATH, 'templates')),
    ],
    'OPTIONS': {
        'context_processors': {
            'django.template.context_processors.request',
            'django.template.context_processors.media',
            'django.contrib.auth.context_processors.auth',
            'myapp.context_processor.theme',
        },
        'debug': False,
    }
}]

However, for some reason, it is not always being executed, mainly in the login page.

This is the view that handles the login URL and return a 'TemplateResponse`:

@never_cache
@sensitive_post_parameters('password')
@csrf_protect
def custom_login(request):

    redirect_field_name = 'next'
    redirect_to = request.POST.get(redirect_field_name,
                                   request.GET.get(redirect_field_name, ''))

    if request.method == "POST":
        form = AuthenticationForm(request, data=request.POST)
        if form.is_valid():

            # Ensure the user-originating redirection url is safe.
            if not is_safe_url(url=redirect_to, host=request.get_host()):
                redirect_to = resolve_url(settings.LOGIN_REDIRECT_URL)

            # Okay, security check complete. Log the user in.
            auth_login(request, form.get_user())

            if getattr(settings, 'CHECK_PERMISSIONS_ON_CMDB', False):
                logger.info('Checking permissions on CMDB.')
                auth_cmdb_user_realms(form.get_user())

            return HttpResponseRedirect(redirect_to)
    else:
        form = AuthenticationForm(request)

    context = {
        'form': form,
        'version': get_project_version(),
        redirect_field_name: redirect_to,
    }

    if hasattr(settings, "CUSTOM_THEME"):
        login_template = 'custom_auth/themes/{}/login.html'.\
             format(settings.CUSTOM_THEME)
    else:
        login_template = 'custom_auth/themes/default/login.html'

    return TemplateResponse(request, login_template, context)

Since the context processor is not being run, the variable ustom_theme` is not being inserted in the context and I get the following error:

VariableDoesNotExist: Failed lookup for key [custom_theme] in u"[{'False': False, 'None': None, 'True': True, 'compressed': {'name': None}}]"

The strange thing is that sometimes the context processor is being executed.

Does anybody have any idea why te context processor is not being run when trying to load the login page?

Answer 1

Context processors is not used if you doesn't call it.

The long path:

return render_to_response("my_app/my_template.html", {'some_var': 'foo'},
                           context_instance=RequestContext(request))

The short path:

from django.shortcuts import render

def some_view(request):
   ...Do something....
   return render(request, "MyTemplate.html",{})