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Reverse for 'book-detail' with arguments '('',)' not found. 1 pattern(s) tried: ['catalog/book/(?P<pk>[0-9]+)$']

My website is working well on my local environment, as well as it has been working well on heroku env until my recent deployment. Code is same on both environments and I referred to all 11 posts related to similar issue,example Reverse for 'todo-user' with arguments '('',)' not found. 1 pattern(s) tried

My issue looks different than what I have seen in other posts here, I think it is related to environment settings/variables, which I am not able to identify it yet. But the solutions provided on stack overflow, makes me think like the real problem of this issue is something else.

When I try to click on http://127.0.0.1:8000/catalog/mybooks/ link, local website works fine, however, production (heroku), same code throws following exception

NoReverseMatch at /catalog/mybooks/
Reverse for 'book-detail' with arguments '('',)' not found. 1 pattern(s) tried: ['catalog/book/(?P<pk>[0-9]+)$']
Request Method: GET
Request URL:    https://<myapp>.herokuapp.com/catalog/mybooks/
Django Version: 2.2.5
Exception Type: NoReverseMatch
Exception Value:    
 Reverse for 'book-detail' with arguments '('',)' not found. 1 pattern(s) tried: ['catalog/book/(?P<pk>[0-9]+)$']
 Exception Location:    /app/.heroku/python/lib/python3.7/site-packages/django/urls/resolvers.py in _reverse_with_prefix, line 673
 Python Executable: /app/.heroku/python/bin/python
 Python Version:    3.7.3
 Python Path:   
['/app/.heroku/python/bin',
 '/app',
 '/app/.heroku/python/lib/python37.zip',
 '/app/.heroku/python/lib/python3.7',
 '/app/.heroku/python/lib/python3.7/lib-dynload',
 '/app/.heroku/python/lib/python3.7/site-packages']
 Server time:   Wed, 9 Oct 2019 04:52:47 +0000
 Error during template rendering
 In template /app/catalog/templates/base_generic.html, error at line 7
 Reverse for 'book-detail' with arguments '('',)' not found. 1 pattern(s) tried: ['catalog/book/(?P<pk>[0-9]+)$']

This looks like a misleading error to me.

Also, because the code is working as expected on my local (ie, showing me all the data), so it doesn't look like a coding issue and so I am not able to understand real problem here (and provided solutions for other similar issues)

I have applied all migrations, so environment looks okay: 

$ heroku run python manage.py migrate --remote heroku-prod
 Running python manage.py migrate on <my app>... starting, run.5216 (Free)
 Running python manage.py migrate on <my app>... connecting, run.5216 (Free)
 Running python manage.py migrate on <my app>... up, run.5216 (Free)
 Operations to perform:
  Apply all migrations: admin, auth, catalog, contenttypes, sessions, social_django
 Running migrations:
  No migrations to apply.

HP@HP-PC MINGW64 ~/git_projects/prod/django_local_library (master)

Code on DEV/staging, that is also same.

Code: urls.py for links related to book

urlpatterns = [
    path('books/', views.BookListView.as_view(), name='books'),
    path('book/<int:pk>', views.BookDetailView.as_view(), name='book-detail'),
    path('mybooks/', views.LoanedBooksByUserListView.as_view(), name='my-borrowed'),
]

views.py

class BookDetailView(LoginRequiredMixin, generic.DetailView):
    model = Book

    def get_context_data(self, **kwargs):
        context = super(BookDetailView, self).get_context_data(**kwargs)
        process_data(self.request)
        return context

class LoanedBooksByUserListView(LoginRequiredMixin, generic.ListView):
    """Generic class-based view listing books on loan to current user. """
    model = BookInstance
    template_name = 'catalog/bookinstance_list_borrowed_user.html'

    def get_queryset(self):
        return BookInstance.objects.filter(borrower=self.request.user).filter(status__exact='o').order_by('due_back')

    def get_context_data(self, **kwargs):
        context = super(LoanedBooksByUserListView, self).get_context_data(**kwargs)
        process_data(self.request)
        return context

Template

{% for bookinst in bookinstance_list %}
      <li class="{% if bookinst.is_overdue %}text-danger{% endif %}">
        <a href="{% url 'book-detail' bookinst.book.pk %}">{{bookinst.book.title}}</a> ({{ bookinst.due_back }})
      </li>
      {% endfor %}

Yesterday night, after this post, I turned off DEBUG for security purpose, ie set DEBUG=False for staging env, as well as for local and added host on ALLOWED_HOSTS, local and staging work fine, however prod is throwing 500 error:

FYI: staging and prod have same configurations, except host name

Ref Setting DEBUG = False causes 500 Error

If I rollback to previous committed code, it starts throwing error highighted in this ques

And if I verify directly on heroku

HP@HP-PC MINGW64 ~/git_projects/prod/django_local_library (master) $ heroku run python manage.py runserver --remote heroku-prod

It doesn't throw any exception:

Performing system checks...
System check identified no issues (0 silenced).
October 09, 2019 - 21:18:54
Django version 2.2.5, using settings 'locallibrary.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

Even the staging logs have no error.

Please help me if someone has ever faced any such issue.

Solution

  • Solution to my problem was fixed when I followed What is a NoReverseMatch error, and how do I fix it? and NoReverseMatch django - not a valid view function or pattern

    And I think all such/similar issues should point to the above link.

    Root cause: Data was corrupted, I deleted corrupted data, and the issue was fixed without any change in the code.

    Steps: I faced similar issue for another new page that I added recently, but the root cause was different (it was due to url formed was incorrect), and the above link helped me identifying the real cause of this issue. I carefully looked into details, including url formed and the page from where url was being referred and finally the data. And the website currently looks like this https://www.realityseekers.com/