Heroku NameError: uninitialized constant MongoMapper::Railtie::YAML

[Deekor]

I am trying to push a Rails 4 app using MongoMapper to Heroku for the first time.

I am getting the error:

remote:        Running: rake assets:precompile
remote:        rake aborted!
remote:        NameError: uninitialized constant MongoMapper::Railtie::YAML

What am I doing wrong?

[kg1990]

you can try

require 'yaml' 

in you Gemfile

[djroze]

I encountered this issue as well when executing in production mode a Rails app that uses MongoMapper v.0.13.1. The problem did not arise when running in development mode. I added a require 'yaml' to my config/application.rb, as follows (this seemed to me like a more suitable place than Gemfile):

require "rails"
require "yaml"
# Pick the frameworks you want:

Would be curious to know if this is a bug in the library or if there's a change that needs to be made to some environment-specific initializer in the Rails app (e.g. something getting loaded/required in development mode that shouldn't be restricted to that mode only).