From 6f5ce21ff5330bec3e1a0099e7de85caf654b8dd Mon Sep 17 00:00:00 2001
From: Aaron Wheeler <aaronwheeler@aaron-wheelers-macbook-pro-15.local>
Date: Wed, 2 Apr 2008 17:25:37 +0900
Subject: [PATCH] Added more robust error message plus additional docs explaining how action-args
 defaults cannot evaluate to nil.

---
 merb-action-args/README                            |   28 +++++++++++++++++++-
 .../lib/merb-action-args/abstract_controller.rb    |    2 +-
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/merb-action-args/README b/merb-action-args/README
index b461e30..83be834 100644
--- a/merb-action-args/README
+++ b/merb-action-args/README
@@ -46,4 +46,30 @@ end
 
 The interesting thing here is that hitting "/foo/bar?one=uno&three=three" will call
 foo("uno", "dos", "three"). In other words, the defaults can be in any order, and 
-merb-action-args will figure out where to fill in the holes.
\ No newline at end of file
+merb-action-args will figure out where to fill in the holes.
+
+There is one important limitation on argument defaults, though: they cannot evaluate
+to false.  So setting a default as nil or false, and then not passing in that
+parameter will raise a BadRequest exception.
+
+{{[
+class Foo < Merb::Controller
+  def bar(id = nil)
+    id || 'there was no id passed in'
+  end
+end
+]}}
+
+Hitting "/bar" will raise a BadRequest.
+
+Hitting "/bar/1" will call bar(1)
+
+A good work-around is to use the empty string as the default.
+
+{{[
+class Foo < Merb::Controller
+  def bar(id = '')
+    id.blank? 'there was no id passed in' : id
+  end
+end
+]}}
diff --git a/merb-action-args/lib/merb-action-args/abstract_controller.rb b/merb-action-args/lib/merb-action-args/abstract_controller.rb
index f941907..8bdbda6 100644
--- a/merb-action-args/lib/merb-action-args/abstract_controller.rb
+++ b/merb-action-args/lib/merb-action-args/abstract_controller.rb
@@ -28,7 +28,7 @@ class Merb::AbstractController
     args = self.class.action_argument_list[action].map do |arg, default|
       arg = arg
       p = params.key?(arg.to_sym)
-      raise BadRequest unless p || default
+      raise(BadRequest, "Expected to find value for arg :#{arg}, or a default value that doesn't evaluate to false") unless p || default
       p ? params[arg.to_sym] : default
     end
     __send__(action, *args)
-- 
1.5.3.1