Django NoReverseMatch and wrong URL Pattern matching attempt

Question

I am new to Django and trying to learn by creating a Blog App.

Now I ran into an error I am not able to solve. I tried everything and compared it to the tutorial I am following but it seems to be the same but for me it is not working.

So I have some posts which are listed on my feed page and when I want to click on the post title to get to the 'post-detail' page I am getting a NoReverseMatch Error because Django somehow tries to match with a wrong URL pattern, which is 'user-feed' but instead I am expecting to match with 'post-detail' .

Error Message:

Reverse for 'user-feed' with arguments '('',)' not found. 2 pattern(s) tried: ['feed/user/(?P<username>[^/]+)/$', 'user/(?P<username>[^/]+)/$']

Feed.html:

{% for post in posts %}
        <article class="media content-section">
            <img class="rounded-circle article-img" src="{{ post.author.profile.image.url }}">
            <div class="media-body">
            <div class="article-metadata">
                <a class="mr-2" href="{% url 'user-feed' post.author.username %}">{{ post.author }}</a>
                <small class="text-muted">{{ post.date_posted|date:"d. F Y" }}</small>
            </div>
            <h2><a class="article-title" href="{% url 'post-detail' post.id %}">{{ post.title }}</a></h2>
            <p class="article-content">{{ post.content }}</p>
            </div>
        </article>
{% endfor %} 

My urls.py for my feed app looks as follows:

urlpatterns = [
    path('', login_required(PostListView.as_view()), name='feed-home'),
    path('user/<str:username>/', login_required(UserPostListView.as_view()), name='user-feed'),
    path('post/<int:pk>/', login_required(PostDetailView.as_view()), name='post-detail'),
    path('post/new/', login_required(PostCreateView.as_view()), name='post-create'),
    path('post/<int:pk>/update', login_required(PostUpdateView.as_view()), name='post-update'),
    path('post/<int:pk>/delete', login_required(PostDeleteView.as_view()), name='post-delete'),
    path('about/', views.about, name='feed-about'),
]

My views.py looks like this:

class PostListView(ListView):
    model = Post
    template_name = 'feed/feed.html' # Replaces the original template src which is <app>/<model>_<viewtype>.html
    context_object_name = 'posts'
    ordering = ['-date_posted']
    paginate_by = 10

class UserPostListView(ListView):
    model = Post
    template_name = 'feed/user_feed.html' # Replaces the original template src which is <app>/<model>_<viewtype>.html
    context_object_name = 'posts'
    ordering = ['-date_posted']
    paginate_by = 10

    def get_queryset(self):
        user = get_object_or_404(User, username=self.kwargs.get('username'))
        return Post.objects.filter(author=user).order_by('-date_posted')


class PostDetailView(DetailView):
    model = Post

class PostCreateView(CreateView):
    model = Post
    fields = ['title', 'content']

    def form_valid(self, form):
        form.instance.author = self.request.user
        return super().form_valid(form)

class PostUpdateView(UserPassesTestMixin, UpdateView):
    model = Post
    fields = ['title', 'content']

    def form_valid(self, form):
        form.instance.author = self.request.user
        return super().form_valid(form)

    # Function to test whether the current user is the author of the post he wants to edit
    def test_func(self):
        post = self.get_object()
        if self.request.user == post.author:
            return True
        return False

class PostDeleteView(UserPassesTestMixin, DeleteView):
    model = Post
    success_url = '/'

    # Function to test whether the current user is the author of the post he wants to delete
    def test_func(self):
        post = self.get_object()
        if self.request.user == post.author:
            return True
        return False

My models.py looks as follows:

class Post(models.Model):
    title = models.CharField(max_length=100)
    content = models.TextField()
    date_posted = models.DateTimeField(default=timezone.now)
    author = models.ForeignKey(User, on_delete=models.CASCADE)

    def __str__(self):
        return self.title

    def get_absolute_url(self):
        return reverse('post-detail', kwargs={'pk': self.pk})

Before this error occurred I deleted some old posts using the django admin page.

Answer 1

I suspect it has a problem with this line:

<a class="mr-2" href="{% url 'user-feed' post.author.username %}">{{ post.author }}</a>

Most likely the post.author.username is not checking out, is it trying to access the author of one of the posts you deleted?