Not able to setup custom page inside superset

[maclynnbrandlock]

Bug description

Not able to setup custom page inside superset

when adding

from flask_appbuilder import BaseView, expose
from superset.extensions import appbuilder

class MyCustomView(BaseView):
route_base = "/custom"

@expose("/")
def index(self):
    return "Custom Page Working ✅"

appbuilder.add_view_no_menu(MyCustomView())

/home/ubuntu/
├── superset_env/ # virtualenv
│ └── lib/python3.10/site-packages/superset/
│
├── custom_app/
│ ├── init.py
│ └── custom_view.py
│
└── superset_config.py

superset startup fails

Screenshots/recordings

No response

Superset version

master / latest-dev

Python version

3.9

Node version

16

Browser

Chrome

Additional context

No response

Checklist

• I have searched Superset docs and Slack and didn't find a solution to my problem.
• I have searched the GitHub issue tracker and didn't find a similar bug report.
• I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.

[dosubot[bot]]

The issue is that you're calling appbuilder.add_view_no_menu() at module import time, but the appbuilder object isn't fully initialized yet during import.

The correct approach is to use FLASK_APP_MUTATOR in your superset_config.py:

from flask_appbuilder import BaseView, expose

class MyCustomView(BaseView):
    route_base = "/custom"
    
    @expose("/")
    def index(self):
        return "Custom Page Working ✅"

def mutate_app(app):
    from superset.extensions import appbuilder
    appbuilder.add_view_no_menu(MyCustomView())
    return app

FLASK_APP_MUTATOR = mutate_app

This registers your view during app initialization when appbuilder is ready, rather than at module import time. You can put everything directly in superset_config.py — no need for the separate custom_app/ directory structure.

Note: Only one FLASK_APP_MUTATOR is supported, so if you need multiple customizations, combine them in a single function. See this discussion for more details.

To reply, just mention @dosu.

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