Address problems with autoloading by searching for constants in instance

Author: myxoh

lib/grape/api.rb

@@ -6,7 +6,7 @@ module Grape
   # should subclass this class in order to build an API.
   class API
     # Class methods that we want to call on the API rather than on the API object
-    NON_OVERRIDABLE = %I[define_singleton_method instance_variable_set inspect class is_a? ! kind_of? respond_to?].freeze
+    NON_OVERRIDABLE = %I[define_singleton_method instance_variable_set inspect class is_a? ! kind_of? respond_to? const_defined? const_missing].freeze
 
     class << self
       attr_accessor :base_instance, :instances
@@ -45,6 +45,15 @@ def api.inherited(child_api)
         end
       end
 
+      # Alleviates problems with autoloading by tring to search for the constant
+      def const_missing(*args)
+        if base_instance.const_defined?(*args)
+          base_instance.const_missing(*args)
+        else
+          super
+        end
+      end
+
       # The remountable class can have a configuration hash to provide some dynamic class-level variables.
       # For instance, a descripcion could be done using: `desc configuration[:description]` if it may vary
       # depending on where the endpoint is mounted. Use with care, if you find yourself using configuration