From c3076f0b6923f595f3d70eb849eeb8b0b204da3b Mon Sep 17 00:00:00 2001
From: Martin Afanasjew <martin@afanasjew.de>
Date: Sat, 16 Apr 2016 20:58:20 +0200
Subject: [PATCH] formulary: use FormulaClassUnavailableError

Present a more helpful error message if a formula file was loaded, but
the class(es) therein didn't match the expected formula class name.
---
 Library/Homebrew/formulary.rb | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Library/Homebrew/formulary.rb b/Library/Homebrew/formulary.rb
index 79e4c946bd..28e79c68f8 100644
--- a/Library/Homebrew/formulary.rb
+++ b/Library/Homebrew/formulary.rb
@@ -23,8 +23,12 @@ class Formulary
 
     begin
       mod.const_get(class_name)
-    rescue NameError => e
-      raise FormulaUnavailableError, name, e.backtrace
+    rescue NameError => original_exception
+      class_list = mod.constants.
+        map { |const_name| mod.const_get(const_name) }.
+        select { |const| const.is_a?(Class) }
+      e = FormulaClassUnavailableError.new(name, path, class_name, class_list)
+      raise e, "", original_exception.backtrace
     end
   end