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>

12 files changed, 40 insertions, 22 deletions

diff --git a/Library/Homebrew/cmd/info.rb b/Library/Homebrew/cmd/info.rb
index a2b491e05..52d39ca15 100644
--- a/Library/Homebrew/cmd/info.rb
+++ b/Library/Homebrew/cmd/info.rb
@@ -69,7 +69,7 @@ module Homebrew
   def github_info(f)
     if f.tap?
       user, repo = f.tap.split("/", 2)
-      tap = Tap.new user, repo.gsub(/^homebrew-/, "")
+      tap = Tap.fetch user, repo.gsub(/^homebrew-/, "")
       if remote = tap.remote
         path = f.path.relative_path_from(tap.path)
         github_remote_path(remote, path)
diff --git a/Library/Homebrew/cmd/readall.rb b/Library/Homebrew/cmd/readall.rb
index 81eaba37d..5e87fcbdb 100644
--- a/Library/Homebrew/cmd/readall.rb
+++ b/Library/Homebrew/cmd/readall.rb
@@ -46,7 +46,7 @@ module Homebrew
     if ARGV.named.empty?
       formulae = Formula.files
     else
-      tap = Tap.new(*tap_args)
+      tap = Tap.fetch(*tap_args)
       raise TapUnavailableError, tap.name unless tap.installed?
       formulae = tap.formula_files
     end
diff --git a/Library/Homebrew/cmd/tap-info.rb b/Library/Homebrew/cmd/tap-info.rb
index 1354264df..dc979af7e 100644
--- a/Library/Homebrew/cmd/tap-info.rb
+++ b/Library/Homebrew/cmd/tap-info.rb
@@ -6,7 +6,7 @@ module Homebrew
       taps = Tap
     else
       taps = ARGV.named.map do |name|
-        Tap.new(*tap_args(name))
+        Tap.fetch(*tap_args(name))
       end
     end
 
diff --git a/Library/Homebrew/cmd/tap-pin.rb b/Library/Homebrew/cmd/tap-pin.rb
index 40888428a..80f1f762a 100644
--- a/Library/Homebrew/cmd/tap-pin.rb
+++ b/Library/Homebrew/cmd/tap-pin.rb
@@ -3,7 +3,7 @@ require "cmd/tap"
 module Homebrew
   def tap_pin
     ARGV.named.each do |name|
-      tap = Tap.new(*tap_args(name))
+      tap = Tap.fetch(*tap_args(name))
       tap.pin
       ohai "Pinned #{tap.name}"
     end
diff --git a/Library/Homebrew/cmd/tap-unpin.rb b/Library/Homebrew/cmd/tap-unpin.rb
index 4462ce68d..641b7c945 100644
--- a/Library/Homebrew/cmd/tap-unpin.rb
+++ b/Library/Homebrew/cmd/tap-unpin.rb
@@ -3,7 +3,7 @@ require "cmd/tap"
 module Homebrew
   def tap_unpin
     ARGV.named.each do |name|
-      tap = Tap.new(*tap_args(name))
+      tap = Tap.fetch(*tap_args(name))
       tap.unpin
       ohai "Unpinned #{tap.name}"
     end
diff --git a/Library/Homebrew/cmd/tap.rb b/Library/Homebrew/cmd/tap.rb
index 291407aff..294106b3c 100644
--- a/Library/Homebrew/cmd/tap.rb
+++ b/Library/Homebrew/cmd/tap.rb
@@ -23,7 +23,7 @@ module Homebrew
     # ensure git is installed
     Utils.ensure_git_installed!
 
-    tap = Tap.new user, repo
+    tap = Tap.fetch user, repo
     return false if tap.installed?
     ohai "Tapping #{tap}"
     remote = clone_target || "https://github.com/#{tap.user}/homebrew-#{tap.repo}"
diff --git a/Library/Homebrew/cmd/test-bot.rb b/Library/Homebrew/cmd/test-bot.rb
index 66f23d873..658f042f9 100644
--- a/Library/Homebrew/cmd/test-bot.rb
+++ b/Library/Homebrew/cmd/test-bot.rb
@@ -39,20 +39,20 @@ module Homebrew
 
   def resolve_test_tap
     tap = ARGV.value("tap")
-    return Tap.new(*tap_args(tap)) if tap
+    return Tap.fetch(*tap_args(tap)) if tap
 
     if ENV["UPSTREAM_BOT_PARAMS"]
       bot_argv = ENV["UPSTREAM_BOT_PARAMS"].split " "
       bot_argv.extend HomebrewArgvExtension
       tap = bot_argv.value("tap")
-      return Tap.new(*tap_args(tap)) if tap
+      return Tap.fetch(*tap_args(tap)) if tap
     end
 
     if git_url = ENV["UPSTREAM_GIT_URL"] || ENV["GIT_URL"]
       # Also can get tap from Jenkins GIT_URL.
       url_path = git_url.sub(%r{^https?://github\.com/}, "").chomp("/")
       HOMEBREW_TAP_ARGS_REGEX =~ url_path
-      return Tap.new($1, $3) if $1 && $3 && $3 != "homebrew"
+      return Tap.fetch($1, $3) if $1 && $3 && $3 != "homebrew"
     end
 
     # return nil means we are testing core repo.
diff --git a/Library/Homebrew/cmd/untap.rb b/Library/Homebrew/cmd/untap.rb
index 22dab7383..c70a0d007 100644
--- a/Library/Homebrew/cmd/untap.rb
+++ b/Library/Homebrew/cmd/untap.rb
@@ -6,7 +6,7 @@ module Homebrew
     raise "Usage is `brew untap <tap-name>`" if ARGV.empty?
 
     ARGV.named.each do |tapname|
-      tap = Tap.new(*tap_args(tapname))
+      tap = Tap.fetch(*tap_args(tapname))
 
       raise TapUnavailableError, tap.name unless tap.installed?
       puts "Untapping #{tap}... (#{tap.path.abv})"
diff --git a/Library/Homebrew/cmd/update.rb b/Library/Homebrew/cmd/update.rb
index 917244a8d..b50348bcf 100644
--- a/Library/Homebrew/cmd/update.rb
+++ b/Library/Homebrew/cmd/update.rb
@@ -63,6 +63,8 @@ module Homebrew
       end
     end
 
+    Tap.clear_cache
+
     # automatically tap any migrated formulae's new tap
     report.select_formula(:D).each do |f|
       next unless (dir = HOMEBREW_CELLAR/f).exist?
@@ -372,7 +374,7 @@ class Report
         user = $1
         repo = $2.sub("homebrew-", "")
         oldname = path.basename(".rb").to_s
-        next unless newname = Tap.new(user, repo).formula_renames[oldname]
+        next unless newname = Tap.fetch(user, repo).formula_renames[oldname]
       else
         oldname = path.basename(".rb").to_s
         next unless newname = FORMULA_RENAMES[oldname]
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index d6ed61183..5af681f98 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -273,7 +273,7 @@ class Formula
       end
     elsif tap?
       user, repo = tap.split("/")
-      formula_renames = Tap.new(user, repo.sub("homebrew-", "")).formula_renames
+      formula_renames = Tap.fetch(user, repo.sub("homebrew-", "")).formula_renames
       if formula_renames.value?(name)
         formula_renames.to_a.rassoc(name).first
       end
diff --git a/Library/Homebrew/formulary.rb b/Library/Homebrew/formulary.rb
index a21d6e731..2bdaca752 100644
--- a/Library/Homebrew/formulary.rb
+++ b/Library/Homebrew/formulary.rb
@@ -145,7 +145,7 @@ class Formulary
 
     def initialize(tapped_name)
       user, repo, name = tapped_name.split("/", 3).map(&:downcase)
-      @tap = Tap.new user, repo.sub(/^homebrew-/, "")
+      @tap = Tap.fetch user, repo.sub(/^homebrew-/, "")
       name = @tap.formula_renames.fetch(name, name)
       path = @tap.formula_files.detect { |file| file.basename(".rb").to_s == name }
 
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