Do not raise an exception if an invalid route was generated automatically.

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -1286,7 +1286,7 @@ def add_route(action, options) # :nodoc:
             action = nil
           end
 
-          if !options.fetch(:as) { true }
+          if !options.fetch(:as, true)
             options.delete(:as)
           else
             options[:as] = name_for_action(options[:as], action)
@@ -1472,8 +1472,16 @@ def name_for_action(as, action) #:nodoc:
               [name_prefix, member_name, prefix]
             end
 
-            candidate = name.select(&:present?).join("_").presence
-            candidate unless as.nil? && @set.routes.find { |r| r.name == candidate }
+            if candidate = name.select(&:present?).join("_").presence
+              # If a name was not explicitly given, we check if it is valid
+              # and return nil in case it isn't. Otherwise, we pass the invalid name
+              # forward so the underlying router engine treats it and raises an exception.
+              if as.nil?
+                candidate unless @set.routes.find { |r| r.name == candidate } || candidate !~ /\A[_a-z]/i
+              else
+                candidate
+              end
+            end
           end
       end
 

actionpack/test/dispatch/routing_test.rb

@@ -91,6 +91,7 @@ def self.call(params, request)
       match "/local/:action", :controller => "local"
 
       match "/projects/status(.:format)"
+      match "/404", :to => lambda { |env| [404, {"Content-Type" => "text/plain"}, ["NOT FOUND"]] }
 
       constraints(:ip => /192\.168\.1\.\d\d\d/) do
         get 'admin' => "queenbee#index"

activerecord/lib/active_record/relation/delegation.rb

@@ -8,7 +8,7 @@ module Delegation
              :connection, :columns_hash, :auto_explain_threshold_in_seconds, :to => :klass
 
     def self.delegate_to_scoped_klass(method)
-      if method.to_s =~ /[a-z]\w*!?/
+      if method.to_s =~ /\A[a-zA-Z_]\w*[!?]?\z/
         module_eval <<-RUBY, __FILE__, __LINE__ + 1
           def #{method}(*args, &block)
             scoping { @klass.#{method}(*args, &block) }