Managing Django Rest Framework 500 Internal Server Error in React when creating user - reactjs

Question

I am attempting my first React + DRF project. Here is my difficulty. When I try to create a user with an existing username I get a 500 internal server error and I can't seem to catch it or do anything with it in React. It otherwise works perfectly well and I can display errors when retrieving user info (such as: "sure does not exist").
The full traceback of the IntegrityError error I get from the backend is:
Traceback (most recent call last):
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/backends/utils.py", line 89, in _execute
return self.cursor.execute(sql, params)
psycopg2.errors.UniqueViolation: duplicate key value violates unique constraint "users_customuser_username_key"
DETAIL: Key (username)=(kenshiro) already exists.
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/core/handlers/exception.py", line 55, in inner
response = get_response(request)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/core/handlers/base.py", line 197, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
return view_func(*args, **kwargs)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/views/generic/base.py", line 84, in view
return self.dispatch(request, *args, **kwargs)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/rest_framework/views.py", line 509, in dispatch
response = self.handle_exception(exc)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/rest_framework/views.py", line 469, in handle_exception
self.raise_uncaught_exception(exc)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
raise exc
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/rest_framework/views.py", line 506, in dispatch
response = handler(request, *args, **kwargs)
File "/Users/bernardino/Desktop/boombust/users/views.py", line 33, in post
user = serializer.save()
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/rest_framework/serializers.py", line 212, in save
self.instance = self.create(validated_data)
File "/Users/bernardino/Desktop/boombust/users/serializers.py", line 59, in create
instance.save()
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/contrib/auth/base_user.py", line 68, in save
super().save(*args, **kwargs)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/models/base.py", line 806, in save
self.save_base(
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/models/base.py", line 857, in save_base
updated = self._save_table(
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/models/base.py", line 1000, in _save_table
results = self._do_insert(
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/models/base.py", line 1041, in _do_insert
return manager._insert(
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/models/manager.py", line 85, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/models/query.py", line 1434, in _insert
return query.get_compiler(using=using).execute_sql(returning_fields)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/models/sql/compiler.py", line 1621, in execute_sql
cursor.execute(sql, params)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/backends/utils.py", line 103, in execute
return super().execute(sql, params)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/backends/utils.py", line 67, in execute
return self._execute_with_wrappers(
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/backends/utils.py", line 80, in _execute_with_wrappers
return executor(sql, params, many, context)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/backends/utils.py", line 89, in _execute
return self.cursor.execute(sql, params)
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/utils.py", line 91, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/Users/bernardino/Desktop/boombust/.env/lib/python3.8/site-packages/django/db/backends/utils.py", line 89, in _execute
return self.cursor.execute(sql, params)
django.db.utils.IntegrityError: duplicate key value violates unique constraint "users_customuser_username_key"
DETAIL: Key (username)=(kenshiro) already exists.
The view in views.py is:
class CustomUserCreate(APIView):
permission_classes = (permissions.AllowAny,)
def post(self, request, format='json'):
serializer = CustomUserSerializer(data=request.data)
if serializer.is_valid(raise_exception=True):
try:
user = serializer.save()
if user:
json = serializer.data
return Response(json, status=status.HTTP_201_CREATED)
except IntegrityError:
return Response({"error": "This username is already taken."}, status=status.HTTP_406_NOT_ACCEPTABLE)
return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
And this is the React logic:
const onSubmit = async (values) => {
const user = {
first_name: values.firstName,
last_name: values.lastName,
username: values.username,
email: values.email,
password: values.password,
};
const response = await fetch(`users/user/create/`, {
method: "POST",
headers: {
Accept: "application/json",
"Content-Type": "application/json",
},
body: JSON.stringify({...user}),
}).catch(err => err);
const text = await response.text();
console.log(response.status);
if (response.status === 201) {
console.log("success", JSON.parse(text));
} else {
console.log("failed", text);
}
};
This is the serializer from serializers.py:
class CustomUserSerializer(serializers.ModelSerializer):
token = serializers.SerializerMethodField()
password = serializers.CharField(write_only=True)
email = serializers.EmailField(
required=True
)
username = serializers.CharField(required=True)
first_name = serializers.CharField(required=True)
last_name = serializers.CharField(required=True)
password = serializers.CharField(
min_length=8, write_only=True, required=True)
class Meta:
model = CustomUser
fields = ('email', 'username', 'password', 'token', 'first_name', 'last_name')
extra_kwargs = {'password': {'write_only': True}}
def get_token(self, user):
refresh = RefreshToken.for_user(user)
return {
'refresh': str(refresh),
'access': str(refresh.access_token),
}
I do have a username = CICharField(unique=True) in the CustomUser class in models.py if it helps.

Answer 1

You need to check before you save the model.
class CustomUserCreate(APIView):
permission_classes = (permissions.AllowAny,)
def post(self, request, format='json'):
serializer = CustomUserSerializer(data=request.data)
if serializer.is_valid(raise_exception=True):
# here you can check if the username already exists or not
username = serializer.validated_data.get('username')
if CustomUser.objects.filter(username = username).count() > 0:
return Response({"error": "This username is already taken."}, status=status.HTTP_406_NOT_ACCEPTABLE)
# if username is new
user = serializer.save()
if user:
json = serializer.data
return Response(json, status=status.HTTP_201_CREATED)
return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)