View didn't return a response

Question

I am working on a python django web app in which I want to implement internationalization and auto translate the whole app into french or chinese.

I took reference from this site https://www.metod.io/en/blog/2015/05/05/django-i18n-part-1/

But whenever I try to run the app it shows this error:

500: ValueError at /en/get_dashboard_data/ The view dashboard.views.getDashboardData didn't return an HttpResponse object. It returned None instead.

And url get_dashboard_data is fetching data through ajax.

url(r'^get_dashboard_data/$', views.getDashboardData, name='getDashboardData'),

view

@login_required(login_url='/')
def getDashboardData(request):
    dbname = request.user.username
    if request.method == 'POST' and request.is_ajax():
        if request.POST.get('action') == 'sale_chart_data':
            data = DashboardData(dbname).getSaleChartData()
            channel_list = data[0]
            data_list = data[1]
            print 123, data_list, channel_list
            return HttpResponse(json.dumps({'channel_list':channel_list, 'data_list':data_list}), content_type='application/json')

        if request.POST.get('action') == 'get_sale_numbers':
            sale_data = DashboardData(dbname).getSaleNumbers()
            return HttpResponse(json.dumps({'sale_number_data':sale_data}), content_type='application/json')

        if request.POST.get('action') == 'get_inventory_numbers':
            inventory_data = DashboardData(dbname).getInventoryData()
            return HttpResponse(json.dumps({'inventory_data':inventory_data}), content_type='application/json')

        if request.POST.get('action') == 'get_order_numbers':
            order_data = DashboardData(dbname).getOrderData()
            return HttpResponse(json.dumps({'order_data':order_data}), content_type='application/json')

        if request.POST.get('action') == 'get_hourly_data':
            order_data = DashboardData(dbname).getHourlyData()
            sale_data = order_data[1]
            count_data = order_data[0]
            return HttpResponse(json.dumps({'sale_data':sale_data, 'count_data':count_data}), content_type='application/json')

        if request.POST.get('action') == 'top_performers':
            data = DashboardData(dbname).getTopPerformers()
            inventory_count_dict = data[0]
            current_month_dict = data[1]
            last_month_dict = data[2]
            current_quarter_dict = data[3]
            current_year_dict = data[4]
            channel_list = data[5]
            return HttpResponse(json.dumps({'inventory_count_dict':inventory_count_dict,'current_month_dict':current_month_dict,'last_month_dict':last_month_dict,'current_quarter_dict':current_quarter_dict,'current_year_dict':current_year_dict,'channel_list':channel_list}), content_type='application/json')

        if request.POST.get('action') == 'top_products':
            product_data = DashboardData(dbname).getTopProducts()
            return HttpResponse(json.dumps({'product_data':product_data}), content_type='application/json')

javascript

function getSaleChart(){
    $.ajax({
        url : "/get_dashboard_data/",
        type : "POST",
        data : {action:'sale_chart_data'},

        success : function(response) {
            channel_list = response.channel_list;
            data_list = response.data_list;
            c3.generate({
                bindto: '#sale-chart-30-days',
                data:{
                    x: 'dates',
                    xFormat: '%b %d',
                    columns: data_list,
                    colors:{
                        Flipkart: '#1AB394',
                        Paytm: '#BABABA'
                    },
                    type: 'bar',
                    groups: [ channel_list ]
                },
                axis: {
                    x: {
                        type: 'timeseries'
                    }
                }
            });
        },

        error : function(xhr,errmsg,err) {
            toastr["error"]("Something Broke.", "Oops !!!.");
            console.log(xhr.status + ": " + xhr.responseText);
        }
    });
}

Answer 1

My guess would be that your JavaScript does indeed make a POST request to /get_dashboard_data/ but it receives a redirect response (HTTP 301 or 302) to /en/get_dashboard_data/ due to some kind of i18n middleware.

The browser follows the redirect, but the new request to /en/get_dashboard_data/ is a GET request.

Edit:

When following a redirect, the browser will always perform the second request as GET, there is no way to prevent that. You have several options to solve this:

• make the initial request to the right application. This means you have to pass your i18n URL into your JavaScript instead of hardcoding it. You can add something like this to your template:

  <script>var dashBoardDataUrl = "{% url "name-of-dashboard-url" %}"</script>

• as your "actions" just get code, you could just accept a GET request and read the action from query paramters

• Split that view into several smaller views that accept GET request so you have something that resembles a REST API.

Answer 2

This is why you should really practice more defensive programming. Though you insist that the request method is POST and it is ajax and the action is sale_chart_data one of the three isn't what you expect it to be.

Your function really should be like follows. It's plain old good practice.

def getDashboardData(request):
    dbname = request.user.username
    if request.method == 'POST' and request.is_ajax():
        action = request.POST.get('action') 
        if action == 'sale_chart_data':
            data = DashboardData(dbname).getSaleChartData()
            ....
        ... 
        # other if conditions here
        else :
            return HttpResponse(json.dumps({'message':'Unknown action {0}'.format(action)}), content_type='application/json')

    else :
            return HttpResponse(json.dumps({'message':'Only ajax post supported'}), content_type='application/json')

And then you ought to set break points and evaluate the request to figure out what exactly is happening in this particular request.