Raise ArgumentError when a symbol can't be mapped to a version

The fact that this is implemented as a hash lookup is an implementation
detail, so don't let the KeyError bubble up.

2 files changed, 9 insertions, 1 deletions

diff --git a/Library/Homebrew/os/mac/version.rb b/Library/Homebrew/os/mac/version.rb
index ed05ac553..06901b642 100644
--- a/Library/Homebrew/os/mac/version.rb
+++ b/Library/Homebrew/os/mac/version.rb
@@ -14,7 +14,10 @@ module OS
       }
 
       def self.from_symbol(sym)
-        new(SYMBOLS.fetch(sym))
+        str = SYMBOLS.fetch(sym) do
+          raise ArgumentError, "unknown version #{sym.inspect}"
+        end
+        new(str)
       end
 
       def initialize(*args)
diff --git a/Library/Homebrew/test/test_version_subclasses.rb b/Library/Homebrew/test/test_version_subclasses.rb
index 1dbaae47a..9261a7251 100644
--- a/Library/Homebrew/test/test_version_subclasses.rb
+++ b/Library/Homebrew/test/test_version_subclasses.rb
@@ -39,4 +39,9 @@ class MacOSVersionTests < Homebrew::TestCase
     assert_operator @v, :===, Version.new("10.7")
     assert_operator @v, :<, Version.new("10.8")
   end
+
+  def test_from_symbol
+    assert_equal @v, MacOS::Version.from_symbol(:lion)
+    assert_raises(ArgumentError) { MacOS::Version.from_symbol(:foo) }
+  end
 end