Prevent repeated lookups of nil-valued keys

Library/Homebrew/macos.rb

@@ -20,8 +20,8 @@ module MacOS extend self
     # Don't call tools (cc, make, strip, etc.) directly!
     # Give the name of the binary you look for as a string to this method
     # in order to get the full path back as a Pathname.
-    @locate ||= {}
-    @locate[tool.to_s] ||= if File.executable? "/usr/bin/#{tool}"
+    (@locate ||= {}).fetch(tool.to_s) do
+      @locate[tool.to_s] = if File.executable? "/usr/bin/#{tool}"
         Pathname.new "/usr/bin/#{tool}"
       else
         # If the tool isn't in /usr/bin, then we first try to use xcrun to find
@@ -38,6 +38,7 @@ module MacOS extend self
         paths.map { |p| Pathname.new(p) }.find { |p| p.executable? }
       end
     end
+  end
 
   def dev_tools_path
     @dev_tools_path ||= if File.exist? "/usr/bin/cc" and File.exist? "/usr/bin/make"
@@ -64,8 +65,8 @@ module MacOS extend self
   end
 
   def sdk_path(v = version)
-    @sdk_path ||= {}
-    @sdk_path[v.to_s] ||= begin
+    (@sdk_path ||= {}).fetch(v.to_s) do
+      @sdk_path[v.to_s] = begin
         opts = []
         # First query Xcode itself
         opts << `#{locate('xcodebuild')} -version -sdk macosx#{v} Path 2>/dev/null`.chomp unless Xcode.bad_xcode_select_path?
@@ -76,6 +77,7 @@ module MacOS extend self
         opts.map{|a| Pathname.new(a) }.detect { |p| p.directory? }
       end
     end
+  end
 
   def default_cc
     cc = locate 'cc'