App crashes on Heroku :-(

[carlesjove]

Working as expected on development. Tests passing.

Running `rails c` attached to terminal... up, run.7511
/app/app/serializers/bill_serializer.rb:6:in `block in <class:BillSerializer>': undefined method `bills_url' for #<Module:0x007f3a1eab8d58> (NoMethodError)
    from /app/vendor/bundle/ruby/2.1.0/gems/collection_json_serializer-0.3.2/lib/collection_json_serializer/serializer.rb:42:in `instance_eval'
    from /app/vendor/bundle/ruby/2.1.0/gems/collection_json_serializer-0.3.2/lib/collection_json_serializer/serializer.rb:42:in `items'
    from /app/app/serializers/bill_serializer.rb:2:in `<class:BillSerializer>'
    from /app/app/serializers/bill_serializer.rb:1:in `<top (required)>'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `block in require'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:240:in `load_dependency'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:360:in `require_or_load'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:317:in `depend_on'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:233:in `require_dependency'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/engine.rb:472:in `block (2 levels) in eager_load!'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/engine.rb:471:in `each'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/engine.rb:471:in `block in eager_load!'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/engine.rb:469:in `each'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/engine.rb:469:in `eager_load!'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/engine.rb:346:in `eager_load!'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/application/finisher.rb:56:in `each'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/application/finisher.rb:56:in `block in <module:Finisher>'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/initializable.rb:30:in `instance_exec'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/initializable.rb:30:in `run'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/initializable.rb:55:in `block in run_initializers'
    from /app/vendor/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:226:in `block in tsort_each'
    from /app/vendor/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:348:in `block (2 levels) in each_strongly_connected_component'
    from /app/vendor/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:427:in `each_strongly_connected_component_from'
    from /app/vendor/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:347:in `block in each_strongly_connected_component'
    from /app/vendor/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:345:in `each'
    from /app/vendor/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:345:in `call'
    from /app/vendor/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:345:in `each_strongly_connected_component'
    from /app/vendor/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:224:in `tsort_each'
    from /app/vendor/ruby-2.1.3/lib/ruby/2.1.0/tsort.rb:205:in `tsort_each'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/initializable.rb:54:in `run_initializers'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/application.rb:352:in `initialize!'
    from /app/config/environment.rb:5:in `<top (required)>'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `block in require'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:240:in `load_dependency'
    from /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/application.rb:328:in `require_environment!'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:142:in `require_application_and_environment!'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:67:in `console'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
    from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.2.0/lib/rails/commands.rb:17:in `<top (required)>'
    from /app/bin/rails:8:in `require'
    from /app/bin/rails:8:in `<main>'

Here's the serializer:

class BillSerializer < CollectionJson::Serializer
  items do
    attributes :id, :description, :subtotal, :total, :vat_amount, :taxes_amount,
               :applicable_vat, :applicable_taxes

    href Rails.application.routes.url_helpers.bills_url << "/{id}"

    links pdf: {
            href: Rails.application.routes.url_helpers.pdf_index_url << "/{id}.pdf"
          }
  end

  template :identifier, :description, :amount, :amount_is, :vat, :taxes

  links create: {
          href: Rails.application.routes.url_helpers.bills_url,
          prompt: "Add a New Bill"
        }
end

[carlesjove]

This are the methods available for Rails.[...].url_helpers on Heroku:

["url_for", "optimize_routes_generation?", "_routes", "url_options",
  "append_features", "included", "class_methods", "freeze", "===", "==",
  "\u003c=\u003e", "\u003c", "\u003c=", "\u003e", "\u003e=", "to_s", "inspect",
  "included_modules", "include?", "name", "ancestors", "instance_methods",
  "public_instance_methods", "protected_instance_methods",
  "private_instance_methods", "constants", "const_get", "const_set",
  "const_defined?", "class_variables", "remove_class_variable",
  "class_variable_get", "class_variable_set", "class_variable_defined?",
  "public_constant", "private_constant", "singleton_class?", "include",
  "prepend", "module_exec", "class_exec", "module_eval", "class_eval",
  "method_defined?", "public_method_defined?", "private_method_defined?",
  "protected_method_defined?", "public_class_method", "private_class_method",
  "autoload", "autoload?", "instance_method", "public_instance_method",
  "mattr_reader", "cattr_reader", "mattr_writer", "cattr_writer",
  "mattr_accessor", "cattr_accessor", "remove_possible_method",
  "redefine_method", "delegate", "alias_method_chain", "alias_attribute",
  "deprecate", "parent_name", "parent", "parents", "local_constants",
  "attr_internal_reader", "attr_internal_writer", "attr_internal_accessor",
  "attr_internal", "anonymous?", "reachable?", "psych_yaml_as", "yaml_as",
  "qualified_const_defined?", "qualified_const_get", "qualified_const_set",
  "methods_transplantable?", "const_missing", "guess_for_anonymous",
  "unloadable", "concerning", "concern", "blank?", "present?", "presence",
  "acts_like?", "duplicable?", "deep_dup", "itself", "try", "try!", "in?",
  "presence_in", "to_param", "to_query", "instance_values",
  "instance_variable_names", "to_json_with_active_support_encoder",
  "to_json_without_active_support_encoder", "to_json", "as_json",
  "with_options", "html_safe?", "psych_to_yaml", "to_yaml",
  "to_yaml_properties", "`", "require_or_load", "require_dependency",
  "load_dependency", "nil?", "=~", "!~", "eql?", "hash", "class",
  "singleton_class", "clone", "dup", "taint", "tainted?", "untaint", "untrust",
  "untrusted?", "trust", "frozen?", "methods", "singleton_methods",
  "protected_methods", "private_methods", "public_methods",
  "instance_variables", "instance_variable_get", "instance_variable_set",
  "instance_variable_defined?", "remove_instance_variable", "instance_of?",
  "kind_of?", "is_a?", "tap", "send", "public_send", "respond_to?", "extend",
  "display", "method", "public_method", "singleton_method",
  "define_singleton_method", "object_id", "to_enum", "enum_for", "gem",
  "silence_warnings", "enable_warnings", "with_warnings", "silence_stderr",
  "silence_stream", "suppress", "capture", "silence", "quietly",
  "suppress_warnings", "equal?", "!", "!=", "instance_eval", "instance_exec",
  "__send__", "__id__"
]

This is the list of methods on development:

["url_for", "optimize_routes_generation?", "_routes", "url_options",
  "pdf_index_path", "pdf_path", "users_path", "user_path", "login_path",
  "expenses_path", "expense_path", "bills_path", "bill_path",
  "rails_info_properties_path", "rails_info_routes_path", "rails_info_path",
  "rails_mailers_path", "pdf_index_url", "pdf_url", "users_url", "user_url",
  "login_url", "expenses_url", "expense_url", "bills_url", "bill_url",
  "rails_info_properties_url", "rails_info_routes_url", "rails_info_url",
  "rails_mailers_url", "append_features", "included", "class_methods", "freeze",
  "===", "==", "\u003c=\u003e", "\u003c", "\u003c=", "\u003e", "\u003e=",
  "to_s", "inspect", "included_modules", "include?", "name", "ancestors",
  "instance_methods", "public_instance_methods", "protected_instance_methods",
  "private_instance_methods", "constants", "const_get", "const_set",
  "const_defined?", "class_variables", "remove_class_variable",
  "class_variable_get", "class_variable_set", "class_variable_defined?",
  "public_constant", "private_constant", "singleton_class?", "include",
  "prepend", "module_exec", "class_exec", "module_eval", "class_eval",
  "method_defined?", "public_method_defined?", "private_method_defined?",
  "protected_method_defined?", "public_class_method", "private_class_method",
  "autoload", "autoload?", "instance_method", "public_instance_method",
  "mattr_reader", "cattr_reader", "mattr_writer", "cattr_writer",
  "mattr_accessor", "cattr_accessor", "remove_possible_method",
  "redefine_method", "delegate", "alias_method_chain", "alias_attribute",
  "deprecate", "parent_name", "parent", "parents", "local_constants",
  "attr_internal_reader", "attr_internal_writer", "attr_internal_accessor",
  "attr_internal", "anonymous?", "reachable?", "psych_yaml_as", "yaml_as",
  "qualified_const_defined?", "qualified_const_get", "qualified_const_set",
  "example_group", "describe", "context", "xdescribe", "xcontext", "fdescribe",
  "fcontext", "shared_examples", "shared_context", "shared_examples_for",
  "methods_transplantable?", "const_missing", "guess_for_anonymous",
  "unloadable", "concerning", "concern", "blank?", "present?", "presence",
  "acts_like?", "duplicable?", "deep_dup", "itself", "try", "try!", "in?",
  "presence_in", "to_param", "to_query", "instance_values",
  "instance_variable_names", "to_json_with_active_support_encoder",
  "to_json_without_active_support_encoder", "to_json", "as_json",
  "with_options", "html_safe?", "psych_to_yaml", "to_yaml",
  "to_yaml_properties", "`", "require_or_load", "require_dependency",
  "load_dependency", "nil?", "=~", "!~", "eql?", "hash", "class",
  "singleton_class", "clone", "dup", "taint", "tainted?", "untaint", "untrust",
  "untrusted?", "trust", "frozen?", "methods", "singleton_methods",
  "protected_methods", "private_methods", "public_methods",
  "instance_variables", "instance_variable_get", "instance_variable_set",
  "instance_variable_defined?", "remove_instance_variable", "instance_of?",
  "kind_of?", "is_a?", "tap", "send", "public_send", "respond_to?", "extend",
  "display", "method", "public_method", "singleton_method",
  "define_singleton_method", "object_id", "to_enum", "enum_for", "gem",
  "silence_warnings", "enable_warnings", "with_warnings", "silence_stderr",
  "silence_stream", "suppress", "capture", "silence", "quietly",
  "suppress_warnings", "equal?", "!", "!=", "instance_eval", "instance_exec",
  "__send__", "__id__"
]

As seen, any of the actual routes is present in production.

[carlesjove]

Open question on Stack Overflow: http://stackoverflow.com/questions/28135924/rails-application-routes-url-helpers-crashing-heroku-app