Improve performance of brew cask list

lib/cask.rb

@@ -111,6 +111,7 @@ def self.set_up_taps
       ohai 'Adding caskroom Tap'
       Homebrew.install_tap(new_user, repo)
     end
+    Cask.reset_all_tapped_cask_dirs
   end
 
   def self.load(query)

lib/cask/cli/list.rb

@@ -45,9 +45,10 @@ def self.list_files(cask)
   end
 
   def self.list_installed
-    columns = Cask.installed.map(&:to_s)
+    installed_casks = Cask.installed
+    columns = installed_casks.map(&:to_s)
     puts_columns columns
-    columns.empty? ? nil : Cask.installed.length == columns.length
+    columns.empty? ? nil : installed_casks.length == columns.length
   end
 
   def self.help

lib/cask/scopes.rb

@@ -8,8 +8,26 @@ def all
       all_titles.map { |c| self.load c }
     end
 
+    def all_tapped_cask_dirs
+      return @all_tapped_cask_dirs unless @all_tapped_cask_dirs.nil?
+      fq_default_tap = tapspath.join(default_tap, 'Casks')
+      @all_tapped_cask_dirs = Dir.glob(tapspath.join('*', '*', 'Casks')).map { |d| Pathname.new(d) }
+      # optimization: place the default Tap first
+      if @all_tapped_cask_dirs.include? fq_default_tap
+        @all_tapped_cask_dirs = @all_tapped_cask_dirs - [ fq_default_tap ]
+        @all_tapped_cask_dirs.unshift fq_default_tap
+      end
+      @all_tapped_cask_dirs
+    end
+
+    def reset_all_tapped_cask_dirs
+      # The memoized value should be reset when a Tap is added/removed
+      # (which is a rare event in our codebase).
+      @all_tapped_cask_dirs = nil
+    end
+
     def all_titles
-      cask_titles = Dir[tapspath.join('*', '*', 'Casks', '*.rb')]
+      cask_titles = all_tapped_cask_dirs.map { |d| Dir.glob d.join('*.rb') }.flatten
       cask_titles.map { |c|
         # => "/usr/local/Library/Taps/caskroom/example-tap/Casks/example.rb"
         c.sub!(/\.rb$/, '')
@@ -24,8 +42,17 @@ def all_titles
 
     def installed
       installed_cask_dirs = Pathname.glob(caskroom.join("*"))
-      installed_cask_dirs.map do |dir|
-        Cask.load(dir.basename.to_s)
+      # Cask.load has some DWIM which is slow.  Optimize here
+      # by spoon-feeding Cask.load fully-qualified paths.
+      # todo: speed up Cask::Source::Tapped (main perf drag is calling Cask.all_titles repeatedly)
+      # todo: ability to specify expected source when calling Cask.load (minor perf benefit)
+      installed_cask_dirs.map do |install_dir|
+        cask_name = install_dir.basename.to_s
+        path_to_cask = all_tapped_cask_dirs.find do |tap_dir|
+          tap_dir.join("#{cask_name}.rb").exist?
+        end
+        cask_name = path_to_cask.join("#{cask_name}.rb") if path_to_cask
+        Cask.load(cask_name)
       end
     end
   end

lib/cask/source/tapped.rb

@@ -4,6 +4,10 @@ def self.me?(query)
   end
 
   def self.path_for_query(query)
+    # Repeating Cask.all_titles is very slow for operations such as
+    # brew cask list, but memoizing the value might cause breakage
+    # elsewhere, given that installation and tap status is permitted
+    # to change during the course of an invocation.
     cask_with_tap = Cask.all_titles.find { |t| t.split('/').last == query.sub(/\.rb$/i,'') }
     if cask_with_tap
       user, repo, cask = cask_with_tap.split('/')

lib/cask/source/untapped_qualified.rb

@@ -9,6 +9,7 @@ def self.path_for_query(query)
     unless Cask.tapspath.join(tap).exist?
       ohai "Adding new tap '#{tap}'"
       Homebrew.install_tap(user, repo)
+      Cask.reset_all_tapped_cask_dirs
     end
     Cask.tapspath.join(tap, 'Casks', "#{cask}.rb")
   end

lib/cask/source/uri.rb

@@ -1,6 +1,6 @@
 class Cask::Source::URI
   def self.me?(query)
-    !!(query =~ URI.regexp)
+    !!(query.to_s =~ URI.regexp)
   end
 
   attr_reader :uri