Could not detect rake tasks

Question

   ensure you can run `$ bundle exec rake -P` against your app with no environment variables present
   and using the production group of your Gemfile.
   This may b         


        

Answer 1

I started getting this strange error all of a sudden yesterday. Heroku confirmed making an update to the Ruby buildpack...

It has to do with the Rakefile. Does your Rakefile require any files? Does it require your app files? If so, then the app should not raise exceptions when it is loaded without any config vars set.

It's counter-intuitive because the app never runs without the config vars set.

In my case, the Sinatra app was looking for database urls in the init file:

uri = URI.parse( ENV[ "REDISTOGO_URL" ])

This will raise an exception if there are no env vars set.

You may have the same issue with other database URL's, such as Mongo or Postgres.

So, protect against missing env vars:

if  ENV[ "REDISTOGO_URL" ]
  uri = URI.parse( ENV[ "REDISTOGO_URL" ])
  ...

You can check if it will work before pushing to Heroku by running bundle exec rake -P

Also, make sure all your tests pass after updating your init. Remove any cached init state by restarting Spork or similar.

Reference: Show Rakefile errors in Ruby deploys