Why is my Flask app being detected as node.js on Heroku

Question

I recently made some changes to the structure of my Flask app hosted on heroku and now heroku has decided to detect it as a Node.js app intead of a Python app. My applicatio

Answer 1

The problem was introduced when I added a package.json to my root directory when I started using npm. It seems that the build detection script runs the nodejs detection first (here) which leads to this code: if [ -f $1/package.json ]; then echo "Node.js" && exit 0 executing and Heroku thinks it's a nodejs app and exits before the python detection has a chance to run.

To solve this I had to manually tell Heroku that I wanted a python build using this command

heroku config:set BUILDPACK_URL=https://github.com/heroku/heroku-buildpack-python.