Don't know how to build task 'default' (even though it exists)

[Morred]

I have several Rack apps I'm deploying on Heroku, and when using this buildpack as described in the readme, deployments started failing with

...
rake aborted!
Don't know how to build task 'default'
...

In my Rakefile I have

begin
  require 'rspec/core/rake_task'
  RSpec::Core::RakeTask.new(:spec)
  task default: :spec
rescue LoadError
end

and when I run bundle exec rake or bundle exec rake default, it works locally (obviously not using the buildpack).

Could this be an issue with the buildpack, or am I just doing it wrong?

[wrozka]

Probably require 'rspec/core/rake_task' raises LoadError which prevents the default task from being defined, and then because the error is ignored in the rescue block you just get the Don't know how to build task 'default'. Please make sure that your code works fine without the rescue LoadError.