Incubator-superset: flask.cli.NoAppException when building superset from master source

[farzad2004]

Make sure these boxes are checked before submitting your issue - thank you!

• [x] I have checked the superset logs for python stacktraces and included it here as text if there are any.
• [x] I have reproduced the issue with at least the latest released version of superset.
• [x] I have checked the issue tracker for the same issue and I haven't found one similar.

I have tried to build superset from master branch to have the filter-box disappear issue sorted. In doing so, I have carefully followed the CONTRIBUTING.MD. All the installation steps were executed successfully. Now, when I start the development server using the "flask run 8080 --with-threads --reload --debugger" command, it starts up successfully. However, the below error is shown on the browser while launching http://127.0.0.1:8080

flask.cli.NoAppException

flask.cli.NoAppException: Failed to find Flask application or factory in module "superset.app". Use "FLASK_APP=superset.app:name to specify one

I have attached the python stack-trace as well as a screenshot showing the error at the browser. I would appreciate if you could help me to resolve this issue. Thanks.
python-stacktrace.txt

[mistercrunch]

Did you skip pip install -r requirements-dev.txt ? Maybe you're missing python-dotenv. Otherwise maybe you are running the flask run command from outside the repo?

[mistercrunch]

Also you might want to try the latest release candidate. https://pypi.org/project/superset/0.29.0rc7/

[farzad2004]

@mistercrunch Thanks a tonne dear Maxime. It finally worked. I did install the requirements-dev.txt. However, the python-dotenv module was not existing in that requirement file. I separately installed python-dotenv through "pip install python-dotenv" and the issue was fixed. The https://pypi.org/project/superset/0.29.0rc7/ has the same python-dotenv module missing in its requirements files. Again, thank you.

[MarcusSorealheis]

only pointing out that @farzad2004 suggested a step that also worked for me: pip install python-dotenv

[MarcusSorealheis]

@farzad2004 @mistercrunch this one line PR should solve the problem for all users going forward. I put it together because there were a lot grumblings: (https://github.com/apache/incubator-superset/pull/6547/commits/465e490a654d6e01838100994951925a29888f0a)

[krdeepak]

I am using docker for installation and getting the same error. How do I fix this error?

[bharath0208]

I am using docker for installation and getting the same error. How do I fix this error?

@krdeepak Any luck with this thing. I am getting the same error now.

assword:
Repeat for confirmation:
Usage: flask fab create-admin [OPTIONS]

Error: A valid Flask application was not obtained from "superset:app".

[gamebusterz]

@bharath0208 I was getting the same error because an earlier version of Superset's docker container was existing (although it was stopped). Deleting the image fixed it for me.