cache taps

There are plenty of IO operations inside Tap object, and it will be more
when implementing formula alias reverse look up(e.g. list all of alias
names for a formula). So let's cache them.

Some benchmark:

$ time brew info $(brew ruby -e 'puts Formula.tap_names') > /dev/null
Before: 6.40s user 2.42s system 96% cpu 9.134 total
After: 4.75s user 0.77s system 97% cpu 5.637 total

Closes Homebrew/homebrew#44377.

Signed-off-by: Xu Cheng <xucheng@me.com>

1 files changed, 25 insertions, 9 deletions

diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index 6efcc3af3..0313de8e8 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -9,6 +9,17 @@ require "utils/json"
 class Tap
   TAP_DIRECTORY = HOMEBREW_LIBRARY/"Taps"
 
+  CACHE = {}
+
+  def self.clear_cache
+    CACHE.clear
+  end
+
+  def self.fetch(user, repo)
+    cache_key = "#{user}/#{repo}".downcase
+    CACHE.fetch(cache_key) { |key| CACHE[key] = Tap.new(user, repo) }
+  end
+
   extend Enumerable
 
   # The user name of this {Tap}. Usually, it's the Github username of
@@ -86,31 +97,33 @@ class Tap
 
   # an array of all {Formula} files of this {Tap}.
   def formula_files
-    dir = [@path/"Formula", @path/"HomebrewFormula", @path].detect(&:directory?)
-    return [] unless dir
-    dir.children.select { |p| p.extname == ".rb" }
+    @formula_files ||= if dir = [@path/"Formula", @path/"HomebrewFormula", @path].detect(&:directory?)
+      dir.children.select { |p| p.extname == ".rb" }
+    else
+      []
+    end
   end
 
   # an array of all {Formula} names of this {Tap}.
   def formula_names
-    formula_files.map { |f| "#{name}/#{f.basename(".rb")}" }
+    @formula_names ||= formula_files.map { |f| "#{name}/#{f.basename(".rb")}" }
   end
 
   # an array of all alias files of this {Tap}.
   # @private
   def alias_files
-    Pathname.glob("#{path}/Aliases/*").select(&:file?)
+    @alias_files ||= Pathname.glob("#{path}/Aliases/*").select(&:file?)
   end
 
   # an array of all aliases of this {Tap}.
   # @private
   def aliases
-    alias_files.map { |f| "#{name}/#{f.basename}" }
+    @aliases ||= alias_files.map { |f| "#{name}/#{f.basename}" }
   end
 
   # an array of all commands files of this {Tap}.
   def command_files
-    Pathname.glob("#{path}/cmd/brew-*").select(&:executable?)
+    @command_files ||= Pathname.glob("#{path}/cmd/brew-*").select(&:executable?)
   end
 
   def pinned_symlink_path
@@ -118,13 +131,15 @@ class Tap
   end
 
   def pinned?
-    @pinned ||= pinned_symlink_path.directory?
+    return @pinned if instance_variable_defined?(:@pinned)
+    @pinned = pinned_symlink_path.directory?
   end
 
   def pin
     raise TapUnavailableError, name unless installed?
     raise TapPinStatusError.new(name, true) if pinned?
     pinned_symlink_path.make_relative_symlink(@path)
+    @pinned = true
   end
 
   def unpin
@@ -132,6 +147,7 @@ class Tap
     raise TapPinStatusError.new(name, false) unless pinned?
     pinned_symlink_path.delete
     pinned_symlink_path.dirname.rmdir_if_possible
+    @pinned = false
   end
 
   def to_hash
@@ -170,7 +186,7 @@ class Tap
 
     TAP_DIRECTORY.subdirs.each do |user|
       user.subdirs.each do |repo|
-        yield new(user.basename.to_s, repo.basename.to_s.sub("homebrew-", ""))
+        yield fetch(user.basename.to_s, repo.basename.to_s.sub("homebrew-", ""))
       end
     end
   end