tap: memoize loading installed taps

This adds a new `Tap.tap_registry` method that will load all
installed and core taps only once instead of doing it every time
on the fly. We only expect this list to change when a tap is
installed or uninstalled in the lifetime of the program. The only
places where that can happen are in the `Tap#install` and
`Tap#uninstall` methods so we make sure to update the tap registry
when those methods are called.

This increase the performance of `Tap#reverse_tap_migrations_renames`
since most of that time was spent in `Tap.each` loading the installed
taps from the tap directory.

On my local computer, the performance goes from 3+ seconds to
around 0.2 when calling `Tap.each(&:to_s)` in a loop 6k times.
6k is around the number of formulae in the core tap so this
is not unheard of.

Other changes:
- Override `Tap#eql?` and `Tap.hash` so we can store them uniquely in sets
- Update tests to check that taps are getting added and removed from the
  registry when they get installed and uninstalled

Library/Homebrew/cmd/tap.rb

@@ -60,7 +60,7 @@ def tap
  tap.fix_remote_configuration
  end
  elsif args.no_named?
- puts Tap.select(&:installed?)
+ puts Tap.select(&:installed?).sort_by(&:name)
  else
  tap = Tap.fetch(args.named.first)
  begin

Library/Homebrew/tap.rb

@@ -5,6 +5,7 @@
 require "completions"
 require "extend/cachable"
 require "description_cache_store"
+require "set"
 require "settings"
 
 # A {Tap} is used to extend the formulae provided by Homebrew core.
@@ -401,6 +402,7 @@ def install(quiet: false, clone_target: nil, force_auto_update: nil,
 
  Commands.rebuild_commands_completion_list
  link_completions_and_manpages
+ Tap.registry << self
 
  formatted_contents = contents.presence&.to_sentence&.dup&.prepend(" ")
  $stderr.puts "Tapped#{formatted_contents} (#{path.abv})." unless quiet
@@ -511,6 +513,7 @@ def uninstall(manual: false)
 
  Commands.rebuild_commands_completion_list
  clear_cache
+ Tap.registry.delete(self)
 
  return if !manual || !official?
 
@@ -880,27 +883,32 @@ def ==(other)
  other = Tap.fetch(other) if other.is_a?(String)
  self.class == other.class && name == other.name
  end
+ alias eql? ==
 
- def self.each(&block)
- return to_enum unless block
+ sig { returns(Integer) }
+ def hash
+ [self.class, name].hash
+ end
 
- installed_taps = if TAP_DIRECTORY.directory?
- TAP_DIRECTORY.subdirs
- .flat_map(&:subdirs)
- .map(&method(:from_path))
- else
- []
- end
+ # A set with all installed and core taps.
+ #
+ # @private
+ sig { returns(T::Set[Tap]) }
+ def self.registry
+ cache[:registry] ||= Set.new.tap do |set|
+ if TAP_DIRECTORY.directory?
+ set.merge TAP_DIRECTORY.subdirs
+ .flat_map(&:subdirs)
+ .map(&method(:from_path))
+ end
 
- available_taps = if Homebrew::EnvConfig.no_install_from_api?
- installed_taps
- else
- default_taps = T.let([CoreTap.instance], T::Array[Tap])
- default_taps << CoreCaskTap.instance if OS.mac? # rubocop:disable Homebrew/MoveToExtendOS
- installed_taps + default_taps
- end.sort_by(&:name).uniq
+ set << CoreTap.instance
+ set << CoreCaskTap.instance if OS.mac? # rubocop:disable Homebrew/MoveToExtendOS
+ end
+ end
 
- available_taps.each(&block)
+ def self.each(&block)
+ registry.each(&block)
  end
 
  # An array of all installed {Tap} names.

Library/Homebrew/test/tap_spec.rb

@@ -140,10 +140,6 @@ def setup_completion(link:)
  end
  end
 
- specify "::names" do
- expect(described_class.names.sort).to eq(["homebrew/core", "homebrew/foo"])
- end
-
  specify "attributes" do
  expect(homebrew_foo_tap.user).to eq("Homebrew")
  expect(homebrew_foo_tap.repo).to eq("foo")
@@ -404,17 +400,20 @@ def setup_completion(link:)
  setup_completion link: true
 
  tap = described_class.new("Homebrew", "bar")
+ expect(described_class.registry).not_to include(tap)
 
  tap.install clone_target: homebrew_foo_tap.path/".git"
 
  expect(tap).to be_installed
+ expect(described_class.registry).to include(tap)
  expect(HOMEBREW_PREFIX/"share/man/man1/brew-tap-cmd.1").to be_a_file
  expect(HOMEBREW_PREFIX/"etc/bash_completion.d/brew-tap-cmd").to be_a_file
  expect(HOMEBREW_PREFIX/"share/zsh/site-functions/_brew-tap-cmd").to be_a_file
  expect(HOMEBREW_PREFIX/"share/fish/vendor_completions.d/brew-tap-cmd.fish").to be_a_file
  tap.uninstall
 
  expect(tap).not_to be_installed
+ expect(described_class.registry).not_to include(tap)
  expect(HOMEBREW_PREFIX/"share/man/man1/brew-tap-cmd.1").not_to exist
  expect(HOMEBREW_PREFIX/"share/man/man1").not_to exist
  expect(HOMEBREW_PREFIX/"etc/bash_completion.d/brew-tap-cmd").not_to exist
@@ -501,6 +500,24 @@ def setup_completion(link:)
  end
  end
 
+ describe ".registry" do
+ it "includes the core and cask taps by default", :needs_macos do
+ expect(described_class.registry).to include(CoreTap.instance, CoreCaskTap.instance)
+ end
+
+ it "includes the core tap and excludes the cask tap by default", :needs_linux do
+ expect(described_class.registry).to include(CoreTap.instance)
+ expect(described_class.registry).not_to include(CoreCaskTap.instance)
+ end
+
+ it "ignores a second instance of the same tap" do
+ expect { described_class.registry << described_class.new("example", "first") }
+ .to change { described_class.registry.size }.by(1)
+ expect { described_class.registry << described_class.new("example", "first") }
+ .not_to(change { described_class.registry.size })
+ end
+ end
+
  describe "Formula Lists" do
  describe "#formula_renames" do
  it "returns the formula_renames hash" do