Merge pull request #971 from penman/follow_alias

Make `brew upgrade` and `brew outdated` follow alias changes

9 files changed, 607 insertions, 111 deletions

diff --git a/Library/Homebrew/cmd/install.rb b/Library/Homebrew/cmd/install.rb
index b2b3eb7c0..50439ccf9 100644
--- a/Library/Homebrew/cmd/install.rb
+++ b/Library/Homebrew/cmd/install.rb
@@ -133,9 +133,14 @@ module Homebrew
           raise "No devel block is defined for #{f.full_name}"
         end
 
-        if f.installed?
-          msg = "#{f.full_name}-#{f.installed_version} already installed"
-          msg << ", it's just not linked" unless f.linked_keg.symlink? || f.keg_only?
+        current = f if f.installed?
+        current ||= f.old_installed_formulae.first
+
+        if current
+          msg = "#{current.full_name}-#{current.installed_version} already installed"
+          unless current.linked_keg.symlink? || current.keg_only?
+            msg << ", it's just not linked"
+          end
           opoo msg
         elsif f.migration_needed? && !ARGV.force?
           # Check if the formula we try to install is the same as installed
diff --git a/Library/Homebrew/cmd/outdated.rb b/Library/Homebrew/cmd/outdated.rb
index 7afa41df4..dfb64a282 100644
--- a/Library/Homebrew/cmd/outdated.rb
+++ b/Library/Homebrew/cmd/outdated.rb
@@ -43,15 +43,28 @@ module Homebrew
 
     outdated_formulae.each do |f|
       if verbose
-        outdated_versions = f.outdated_versions(fetch_head: fetch_head)
-        current_version = if f.head? && outdated_versions.any? { |v| v.to_s == f.pkg_version.to_s }
+        outdated_kegs = f.outdated_kegs(fetch_head: fetch_head)
+
+        current_version = if f.alias_changed?
+          latest = f.latest_formula
+          "#{latest.name} (#{latest.pkg_version})"
+        elsif f.head? && outdated_kegs.any? { |k| k.version.to_s == f.pkg_version.to_s }
+          # There is a newer HEAD but the version number has not changed.
           "latest HEAD"
         else
           f.pkg_version.to_s
         end
-        puts "#{f.full_name} (#{outdated_versions.join(", ")}) < #{current_version}"
+
+        outdated_versions = outdated_kegs.
+          group_by { |keg| Formulary.from_keg(keg) }.
+          sort_by { |formula, kegs| formula.full_name }.
+          map do |formula, kegs|
+            "#{formula.full_name} (#{kegs.map(&:version).join(", ")})"
+          end.join(", ")
+
+        puts "#{outdated_versions} < #{current_version}"
       else
-        puts f.full_name
+        puts f.full_installed_specified_name
       end
     end
   end
@@ -62,7 +75,7 @@ module Homebrew
     outdated_formulae = formulae.select { |f| f.outdated?(fetch_head: fetch_head) }
 
     outdated = outdated_formulae.each do |f|
-      outdated_versions = f.outdated_versions(fetch_head: fetch_head)
+      outdated_versions = f.outdated_kegs(fetch_head: fetch_head).map(&:version)
       current_version = if f.head? && outdated_versions.any? { |v| v.to_s == f.pkg_version.to_s }
         "HEAD"
       else
diff --git a/Library/Homebrew/cmd/upgrade.rb b/Library/Homebrew/cmd/upgrade.rb
index 6968fbda8..c56a73384 100644
--- a/Library/Homebrew/cmd/upgrade.rb
+++ b/Library/Homebrew/cmd/upgrade.rb
@@ -37,10 +37,10 @@ module Homebrew
       (ARGV.resolved_formulae - outdated).each do |f|
         versions = f.installed_kegs.map(&:version)
         if versions.empty?
-          onoe "#{f.full_name} not installed"
+          onoe "#{f.full_specified_name} not installed"
         else
           version = versions.max
-          onoe "#{f.full_name} #{version} already installed"
+          onoe "#{f.full_specified_name} #{version} already installed"
         end
       end
       exit 1 if outdated.empty?
@@ -51,19 +51,21 @@ module Homebrew
       outdated -= pinned
     end
 
-    if outdated.empty?
+    formulae_to_install = outdated.map(&:latest_formula)
+
+    if formulae_to_install.empty?
       oh1 "No packages to upgrade"
     else
-      oh1 "Upgrading #{outdated.length} outdated package#{plural(outdated.length)}, with result:"
-      puts outdated.map { |f| "#{f.full_name} #{f.pkg_version}" } * ", "
+      oh1 "Upgrading #{formulae_to_install.length} outdated package#{plural(formulae_to_install.length)}, with result:"
+      puts formulae_to_install.map { |f| "#{f.full_specified_name} #{f.pkg_version}" } * ", "
     end
 
     unless upgrade_pinned? || pinned.empty?
       oh1 "Not upgrading #{pinned.length} pinned package#{plural(pinned.length)}:"
-      puts pinned.map { |f| "#{f.full_name} #{f.pkg_version}" } * ", "
+      puts pinned.map { |f| "#{f.full_specified_name} #{f.pkg_version}" } * ", "
     end
 
-    outdated.each do |f|
+    formulae_to_install.each do |f|
       upgrade_formula(f)
       next unless ARGV.include?("--cleanup")
       next unless f.installed?
@@ -76,7 +78,11 @@ module Homebrew
   end
 
   def upgrade_formula(f)
-    outdated_keg = Keg.new(f.linked_keg.resolved_path) if f.linked_keg.directory?
+    formulae_maybe_with_kegs = [f] + f.old_installed_formulae
+    outdated_kegs = formulae_maybe_with_kegs.
+      map(&:linked_keg).
+      select(&:directory?).
+      map { |k| Keg.new(k.resolved_path) }
 
     fi = FormulaInstaller.new(f)
     fi.options             = f.build.used_options
@@ -87,12 +93,12 @@ module Homebrew
     fi.debug               = ARGV.debug?
     fi.prelude
 
-    oh1 "Upgrading #{f.full_name}"
+    oh1 "Upgrading #{f.full_specified_name}"
 
     # first we unlink the currently active keg for this formula otherwise it is
     # possible for the existing build to interfere with the build we are about to
     # do! Seriously, it happens!
-    outdated_keg.unlink if outdated_keg
+    outdated_kegs.each(&:unlink)
 
     fi.install
     fi.finish
@@ -117,7 +123,7 @@ module Homebrew
   ensure
     # restore previous installation state if build failed
     begin
-      outdated_keg.link if outdated_keg && !f.installed?
+      outdated_kegs.each(&:link) if !f.installed?
     rescue
       nil
     end
diff --git a/Library/Homebrew/extend/ARGV.rb b/Library/Homebrew/extend/ARGV.rb
index 63e46a1e2..d9f599877 100644
--- a/Library/Homebrew/extend/ARGV.rb
+++ b/Library/Homebrew/extend/ARGV.rb
@@ -37,11 +37,23 @@ module HomebrewArgvExtension
             f.version.update_commit(k.version.version.commit) if k.version.head?
           end
         end
-        f
       else
         rack = Formulary.to_rack(name)
-        Formulary.from_rack(rack, spec(nil))
+        alias_path = Formulary.factory(name).alias_path
+        f = Formulary.from_rack(rack, spec(nil), alias_path: alias_path)
       end
+
+      # If this formula was installed with an alias that has since changed,
+      # then it was specified explicitly in ARGV. (Using the alias would
+      # instead have found the new formula.)
+      #
+      # Because of this, the user is referring to this specific formula,
+      # not any formula targetted by the same alias, so in this context
+      # the formula shouldn't be considered outdated if the alias used to
+      # install it has changed.
+      f.follow_installed_alias = false
+
+      f
     end
   end
 
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index f40f54110..e3a70fc65 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -60,16 +60,24 @@ class Formula
   # e.g. `this-formula`
   attr_reader :name
 
-  # The name specified when installing this {Formula}.
-  # Could be the name of the {Formula}, or an alias.
-  # e.g. `another-name-for-this-formula`
+  # The path to the alias that was used to identify this {Formula}.
+  # e.g. `/usr/local/Library/Taps/homebrew/homebrew-core/Aliases/another-name-for-this-formula`
   attr_reader :alias_path
 
+  # The name of the alias that was used to identify this {Formula}.
+  # e.g. `another-name-for-this-formula`
+  attr_reader :alias_name
+
   # The fully-qualified name of this {Formula}.
   # For core formula it's the same as {#name}.
   # e.g. `homebrew/tap-name/this-formula`
   attr_reader :full_name
 
+  # The fully-qualified alias referring to this {Formula}.
+  # For core formula it's the same as {#alias_name}.
+  # e.g. `homebrew/tap-name/another-name-for-this-formula`
+  attr_reader :full_alias_name
+
   # The full path to this {Formula}.
   # e.g. `/usr/local/Library/Taps/homebrew/homebrew-core/Formula/this-formula.rb`
   attr_reader :path
@@ -149,25 +157,31 @@ class Formula
   # @return [BuildOptions]
   attr_accessor :build
 
+  # A {Boolean} indicating whether this formula should be considered outdated
+  # if the target of the alias it was installed with has since changed.
+  # Defaults to true.
+  # @return [Boolean]
+  attr_accessor :follow_installed_alias
+  alias follow_installed_alias? follow_installed_alias
+
   # @private
   def initialize(name, path, spec, alias_path: nil)
     @name = name
     @path = path
     @alias_path = alias_path
+    @alias_name = File.basename(alias_path) if alias_path
     @revision = self.class.revision || 0
     @version_scheme = self.class.version_scheme || 0
 
-    if path == Formulary.core_path(name)
-      @tap = CoreTap.instance
-      @full_name = name
+    @tap = if path == Formulary.core_path(name)
+      CoreTap.instance
     elsif path.to_s =~ HOMEBREW_TAP_PATH_REGEX
-      @tap = Tap.fetch($1, $2)
-      @full_name = "#{@tap}/#{name}"
-    else
-      @tap = nil
-      @full_name = name
+      Tap.fetch($1, $2)
     end
 
+    @full_name = get_full_name(name)
+    @full_alias_name = get_full_name(@alias_name)
+
     set_spec :stable
     set_spec :devel
     set_spec :head
@@ -183,6 +197,7 @@ class Formula
     validate_attributes!
     @build = active_spec.build
     @pin = FormulaPin.new(self)
+    @follow_installed_alias = true
   end
 
   # @private
@@ -197,6 +212,16 @@ class Formula
 
   private
 
+  # Allow full name logic to be re-used between names, aliases,
+  # and installed aliases.
+  def get_full_name(name)
+    if name.nil? || @tap.nil? || @tap.core_tap?
+      name
+    else
+      "#{@tap}/#{name}"
+    end
+  end
+
   def set_spec(name)
     spec = self.class.send(name)
     if spec.url
@@ -228,11 +253,47 @@ class Formula
 
   public
 
-  # The path that was specified to find/install this formula.
+  # The alias path that was used to install this formula, if present.
+  # Can differ from alias_path, which is the alias used to find the formula,
+  # and is specified to this instance.
+  def installed_alias_path
+    path = build.source["path"] if build.is_a?(Tab)
+    path if path =~ %r{#{HOMEBREW_TAP_DIR_REGEX}/Aliases}
+  end
+
+  def installed_alias_name
+    File.basename(installed_alias_path) if installed_alias_path
+  end
+
+  def full_installed_alias_name
+    get_full_name(installed_alias_name)
+  end
+
+  # The path that was specified to find this formula.
   def specified_path
     alias_path || path
   end
 
+  # The name specified to find this formula.
+  def specified_name
+    alias_name || name
+  end
+
+  # The name (including tap) specified to find this formula.
+  def full_specified_name
+    full_alias_name || full_name
+  end
+
+  # The name specified to install this formula.
+  def installed_specified_name
+    installed_alias_name || name
+  end
+
+  # The name (including tap) specified to install this formula.
+  def full_installed_specified_name
+    full_installed_alias_name || full_name
+  end
+
   # Is the currently active {SoftwareSpec} a {#stable} build?
   # @private
   def stable?
@@ -503,13 +564,13 @@ class Formula
     prefix.parent
   end
 
-  # All of current installed prefix directories.
+  # All currently installed prefix directories.
   # @private
   def installed_prefixes
     rack.directory? ? rack.subdirs : []
   end
 
-  # All of current installed kegs.
+  # All currently installed kegs.
   # @private
   def installed_kegs
     installed_prefixes.map { |dir| Keg.new(dir) }
@@ -1059,39 +1120,88 @@ class Formula
   end
 
   # @private
-  def outdated_versions(options = {})
-    @outdated_versions ||= Hash.new do |cache, key|
+  def outdated_kegs(options = {})
+    @outdated_kegs ||= Hash.new do |cache, key|
       raise Migrator::MigrationNeededError, self if migration_needed?
-      cache[key] = _outdated_versions(key)
+      cache[key] = _outdated_kegs(key)
     end
-    @outdated_versions[options]
+    @outdated_kegs[options]
   end
 
-  def _outdated_versions(options = {})
-    all_versions = []
+  def _outdated_kegs(options = {})
+    all_kegs = []
 
     installed_kegs.each do |keg|
+      all_kegs << keg
       version = keg.version
-      all_versions << version
       next if version.head?
 
       tab = Tab.for_keg(keg)
       next if version_scheme > tab.version_scheme
       next if version_scheme == tab.version_scheme && pkg_version > version
-      return []
+
+      # don't consider this keg current if there's a newer formula available
+      next if follow_installed_alias? && new_formula_available?
+
+      return [] # this keg is the current version of the formula, so it's not outdated
     end
 
+    # Even if this formula hasn't been installed, there may be installations
+    # of other formulae which used to be targets of the alias currently
+    # targetting this formula. These should be counted as outdated versions.
+    all_kegs.concat old_installed_formulae.flat_map(&:installed_kegs)
+
     head_version = latest_head_version
     if head_version && !head_version_outdated?(head_version, options)
       []
     else
-      all_versions.sort
+      all_kegs.sort_by(&:version)
     end
   end
 
+  def new_formula_available?
+    installed_alias_target_changed? && !latest_formula.installed?
+  end
+
+  def current_installed_alias_target
+    Formulary.factory(installed_alias_path) if installed_alias_path
+  end
+
+  # Has the target of the alias used to install this formula changed?
+  # Returns false if the formula wasn't installed with an alias.
+  def installed_alias_target_changed?
+    target = current_installed_alias_target
+    target && target != self
+  end
+
+  # Is this formula the target of an alias used to install an old formula?
+  def supersedes_an_installed_formula?
+    old_installed_formulae.any?
+  end
+
+  # Has the alias used to install the formula changed, or are different
+  # formulae already installed with this alias?
+  def alias_changed?
+    installed_alias_target_changed? || supersedes_an_installed_formula?
+  end
+
+  # If the alias has changed value, return the new formula.
+  # Otherwise, return self.
+  def latest_formula
+    installed_alias_target_changed? ? current_installed_alias_target : self
+  end
+
+  def old_installed_formulae
+    # If this formula isn't the current target of the alias,
+    # it doesn't make sense to say that other formulae are older versions of it
+    # because we don't know which came first.
+    return [] if alias_path.nil? || installed_alias_target_changed?
+    self.class.installed_with_alias_path(alias_path) - [self]
+  end
+
   # @private
   def outdated?(options = {})
-    !outdated_versions(options).empty?
+    !outdated_kegs(options).empty?
   rescue Migrator::MigrationNeededError
     true
   end
@@ -1246,6 +1356,11 @@ class Formula
     end.compact
   end
 
+  def self.installed_with_alias_path(alias_path)
+    return [] if alias_path.nil?
+    installed.select { |f| f.installed_alias_path == alias_path }
+  end
+
   # an array of all alias files of core {Formula}
   # @private
   def self.core_alias_files
diff --git a/Library/Homebrew/formulary.rb b/Library/Homebrew/formulary.rb
index 1cd9dce2a..4c20c2225 100644
--- a/Library/Homebrew/formulary.rb
+++ b/Library/Homebrew/formulary.rb
@@ -77,8 +77,11 @@ class Formulary
     end
 
     # Gets the formula instance.
-    def get_formula(spec)
-      klass.new(name, path, spec, alias_path: alias_path)
+    #
+    # `alias_path` can be overridden here in case an alias was used to refer to
+    # a formula that was loaded in another way.
+    def get_formula(spec, alias_path: nil)
+      klass.new(name, path, spec, alias_path: alias_path || self.alias_path)
     end
 
     def klass
@@ -103,7 +106,7 @@ class Formulary
       super name, Formulary.path(full_name)
     end
 
-    def get_formula(spec)
+    def get_formula(spec, alias_path: nil)
       formula = super
       formula.local_bottle_path = @bottle_filename
       formula_version = formula.pkg_version
@@ -120,7 +123,7 @@ class Formulary
       path = alias_path.resolved_path
       name = path.basename(".rb").to_s
       super name, path
-      @alias_path = alias_path
+      @alias_path = alias_path.to_s
     end
   end
 
@@ -175,7 +178,7 @@ class Formulary
       super name, path
     end
 
-    def get_formula(spec)
+    def get_formula(spec, alias_path: nil)
       super
     rescue FormulaUnavailableError => e
       raise TapFormulaUnavailableError.new(tap, name), "", e.backtrace
@@ -187,7 +190,7 @@ class Formulary
       super name, Formulary.core_path(name)
     end
 
-    def get_formula(_spec)
+    def get_formula(_spec, alias_path: nil)
       raise FormulaUnavailableError, name
     end
   end
@@ -215,38 +218,42 @@ class Formulary
   # * a formula pathname
   # * a formula URL
   # * a local bottle reference
-  def self.factory(ref, spec = :stable)
-    loader_for(ref).get_formula(spec)
+  def self.factory(ref, spec = :stable, alias_path: nil)
+    loader_for(ref).get_formula(spec, alias_path: alias_path)
   end
 
   # Return a Formula instance for the given rack.
   # It will auto resolve formula's spec when requested spec is nil
-  def self.from_rack(rack, spec = nil)
+  #
+  # The :alias_path option will be used if the formula is found not to be
+  # installed, and discarded if it is installed because the alias_path used
+  # to install the formula will be set instead.
+  def self.from_rack(rack, spec = nil, alias_path: nil)
     kegs = rack.directory? ? rack.subdirs.map { |d| Keg.new(d) } : []
     keg = kegs.detect(&:linked?) || kegs.detect(&:optlinked?) || kegs.max_by(&:version)
 
     if keg
-      from_keg(keg, spec)
+      from_keg(keg, spec, :alias_path => alias_path)
     else
-      factory(rack.basename.to_s, spec || :stable)
+      factory(rack.basename.to_s, spec || :stable, :alias_path => alias_path)
     end
   end
 
   # Return a Formula instance for the given keg.
   # It will auto resolve formula's spec when requested spec is nil
-  def self.from_keg(keg, spec = nil)
+  def self.from_keg(keg, spec = nil, alias_path: nil)
     tab = Tab.for_keg(keg)
     tap = tab.tap
     spec ||= tab.spec
 
     f = if tap.nil?
-      factory(keg.rack.basename.to_s, spec)
+      factory(keg.rack.basename.to_s, spec, :alias_path => alias_path)
     else
       begin
-        factory("#{tap}/#{keg.rack.basename}", spec)
+        factory("#{tap}/#{keg.rack.basename}", spec, :alias_path => alias_path)
       rescue FormulaUnavailableError
         # formula may be migrated to different tap. Try to search in core and all taps.
-        factory(keg.rack.basename.to_s, spec)
+        factory(keg.rack.basename.to_s, spec, :alias_path => alias_path)
       end
     end
     f.build = tab
@@ -346,7 +353,7 @@ class Formulary
   end
 
   def self.core_path(name)
-    CoreTap.instance.formula_dir/"#{name.downcase}.rb"
+    CoreTap.instance.formula_dir/"#{name.to_s.downcase}.rb"
   end
 
   def self.tap_paths(name, taps = Dir["#{HOMEBREW_LIBRARY}/Taps/*/*/"])
diff --git a/Library/Homebrew/test/test_formula.rb b/Library/Homebrew/test/test_formula.rb
index 7c09e765f..1da60c214 100644
--- a/Library/Homebrew/test/test_formula.rb
+++ b/Library/Homebrew/test/test_formula.rb
@@ -8,15 +8,153 @@ class FormulaTests < Homebrew::TestCase
     name = "formula_name"
     path = Formulary.core_path(name)
     spec = :stable
-    alias_path = CoreTap.instance.alias_dir/"formula_alias"
+
+    f = klass.new(name, path, spec)
+    assert_equal name, f.name
+    assert_equal name, f.specified_name
+    assert_equal name, f.full_name
+    assert_equal name, f.full_specified_name
+    assert_equal path, f.path
+    assert_nil f.alias_path
+    assert_nil f.alias_name
+    assert_nil f.full_alias_name
+    assert_raises(ArgumentError) { klass.new }
+  end
+
+  def test_formula_instantiation_with_alias
+    klass = Class.new(Formula) { url "http://example.com/foo-1.0.tar.gz" }
+    name = "formula_name"
+    path = Formulary.core_path(name)
+    spec = :stable
+    alias_name = "baz@1"
+    alias_path = CoreTap.instance.alias_dir/alias_name
+
+    f = klass.new(name, path, spec, alias_path: alias_path)
+    assert_equal name, f.name
+    assert_equal name, f.full_name
+    assert_equal path, f.path
+    assert_equal alias_path, f.alias_path
+    assert_equal alias_name, f.alias_name
+    assert_equal alias_name, f.specified_name
+    assert_equal alias_name, f.full_alias_name
+    assert_equal alias_name, f.full_specified_name
+    assert_raises(ArgumentError) { klass.new }
+  end
+
+  def test_tap_formula_instantiation
+    tap = Tap.new("foo", "bar")
+    klass = Class.new(Formula) { url "baz-1.0" }
+    name = "baz"
+    full_name = "#{tap.user}/#{tap.repo}/#{name}"
+    path = tap.path/"Formula/#{name}.rb"
+    spec = :stable
+
+    f = klass.new(name, path, spec)
+    assert_equal name, f.name
+    assert_equal name, f.specified_name
+    assert_equal full_name, f.full_name
+    assert_equal full_name, f.full_specified_name
+    assert_equal path, f.path
+    assert_nil f.alias_path
+    assert_nil f.alias_name
+    assert_nil f.full_alias_name
+    assert_raises(ArgumentError) { klass.new }
+  end
+
+  def test_tap_formula_instantiation_with_alias
+    tap = Tap.new("foo", "bar")
+    klass = Class.new(Formula) { url "baz-1.0" }
+    name = "baz"
+    full_name = "#{tap.user}/#{tap.repo}/#{name}"
+    path = tap.path/"Formula/#{name}.rb"
+    spec = :stable
+    alias_name = "baz@1"
+    full_alias_name = "#{tap.user}/#{tap.repo}/#{alias_name}"
+    alias_path = CoreTap.instance.alias_dir/alias_name
 
     f = klass.new(name, path, spec, alias_path: alias_path)
     assert_equal name, f.name
+    assert_equal full_name, f.full_name
     assert_equal path, f.path
     assert_equal alias_path, f.alias_path
+    assert_equal alias_name, f.alias_name
+    assert_equal alias_name, f.specified_name
+    assert_equal full_alias_name, f.full_alias_name
+    assert_equal full_alias_name, f.full_specified_name
     assert_raises(ArgumentError) { klass.new }
   end
 
+  def test_follow_installed_alias
+    f = formula { url "foo-1.0" }
+    assert_predicate f, :follow_installed_alias?
+
+    f.follow_installed_alias = true
+    assert_predicate f, :follow_installed_alias?
+
+    f.follow_installed_alias = false
+    refute_predicate f, :follow_installed_alias?
+  end
+
+  def test_installed_alias_with_core
+    f = formula { url "foo-1.0" }
+
+    build_values_with_no_installed_alias = [
+      nil,
+      BuildOptions.new({}, {}),
+      Tab.new(source: { "path" => f.path.to_s }),
+    ]
+
+    build_values_with_no_installed_alias.each do |build|
+      f.build = build
+      assert_nil f.installed_alias_path
+      assert_nil f.installed_alias_name
+      assert_nil f.full_installed_alias_name
+      assert_equal f.name, f.installed_specified_name
+      assert_equal f.name, f.full_installed_specified_name
+    end
+
+    alias_name = "bar"
+    alias_path = "#{CoreTap.instance.alias_dir}/#{alias_name}"
+    f.build = Tab.new(source: { "path" => alias_path })
+    assert_equal alias_path, f.installed_alias_path
+    assert_equal alias_name, f.installed_alias_name
+    assert_equal alias_name, f.full_installed_alias_name
+    assert_equal alias_name, f.installed_specified_name
+    assert_equal alias_name, f.full_installed_specified_name
+  end
+
+  def test_installed_alias_with_tap
+    tap = Tap.new("user", "repo")
+    name = "foo"
+    path = "#{tap.path}/Formula/#{name}.rb"
+    f = formula(name, path) { url "foo-1.0" }
+
+    build_values_with_no_installed_alias = [
+      nil,
+      BuildOptions.new({}, {}),
+      Tab.new(source: { "path" => f.path }),
+    ]
+
+    build_values_with_no_installed_alias.each do |build|
+      f.build = build
+      assert_nil f.installed_alias_path
+      assert_nil f.installed_alias_name
+      assert_nil f.full_installed_alias_name
+      assert_equal f.name, f.installed_specified_name
+      assert_equal f.full_name, f.full_installed_specified_name
+    end
+
+    alias_name = "bar"
+    full_alias_name = "#{tap.user}/#{tap.repo}/#{alias_name}"
+    alias_path = "#{tap.alias_dir}/#{alias_name}"
+    f.build = Tab.new(source: { "path" => alias_path })
+    assert_equal alias_path, f.installed_alias_path
+    assert_equal alias_name, f.installed_alias_name
+    assert_equal full_alias_name, f.full_installed_alias_name
+    assert_equal alias_name, f.installed_specified_name
+    assert_equal full_alias_name, f.full_installed_specified_name
+  end
+
   def test_prefix
     f = Testball.new
     assert_equal HOMEBREW_CELLAR/f.name/"0.1", f.prefix
@@ -248,6 +386,62 @@ class FormulaTests < Homebrew::TestCase
     assert_nil Testball.new <=> Object.new
   end
 
+  def test_alias_paths_with_build_options
+    alias_path = CoreTap.instance.alias_dir/"another_name"
+    f = formula(:alias_path => alias_path) { url "foo-1.0" }
+    f.build = BuildOptions.new({}, {})
+    assert_equal alias_path, f.alias_path
+    assert_nil f.installed_alias_path
+  end
+
+  def test_alias_paths_with_tab_with_non_alias_source_path
+    alias_path = CoreTap.instance.alias_dir/"another_name"
+    source_path = CoreTap.instance.formula_dir/"another_other_name"
+    f = formula(:alias_path => alias_path) { url "foo-1.0" }
+    f.build = Tab.new(:source => { "path" => source_path.to_s })
+    assert_equal alias_path, f.alias_path
+    assert_nil f.installed_alias_path
+  end
+
+  def test_alias_paths_with_tab_with_alias_source_path
+    alias_path = CoreTap.instance.alias_dir/"another_name"
+    source_path = CoreTap.instance.alias_dir/"another_other_name"
+    f = formula(:alias_path => alias_path) { url "foo-1.0" }
+    f.build = Tab.new(:source => { "path" => source_path.to_s })
+    assert_equal alias_path, f.alias_path
+    assert_equal source_path.to_s, f.installed_alias_path
+  end
+
+  def test_installed_with_alias_path_with_nil
+    assert_predicate Formula.installed_with_alias_path(nil), :empty?
+  end
+
+  def test_installed_with_alias_path_with_a_path
+    alias_path = "#{CoreTap.instance.alias_dir}/alias"
+    different_alias_path = "#{CoreTap.instance.alias_dir}/another_alias"
+
+    formula_with_alias = formula("foo") { url "foo-1.0" }
+    formula_with_alias.build = Tab.empty
+    formula_with_alias.build.source["path"] = alias_path
+
+    formula_without_alias = formula("bar") { url "bar-1.0" }
+    formula_without_alias.build = Tab.empty
+    formula_without_alias.build.source["path"] = formula_without_alias.path.to_s
+
+    formula_with_different_alias = formula("baz") { url "baz-1.0" }
+    formula_with_different_alias.build = Tab.empty
+    formula_with_different_alias.build.source["path"] = different_alias_path
+
+    formulae = [
+      formula_with_alias,
+      formula_without_alias,
+      formula_with_different_alias,
+    ]
+
+    Formula.stubs(:installed).returns(formulae)
+    assert_equal [formula_with_alias], Formula.installed_with_alias_path(alias_path)
+  end
+
   def test_formula_spec_integration
     f = formula do
       homepage "http://example.com"
@@ -581,29 +775,113 @@ class FormulaTests < Homebrew::TestCase
   end
 end
 
+class AliasChangeTests < Homebrew::TestCase
+  attr_reader :f, :new_formula, :tab, :alias_path
+
+  def make_formula(version)
+    f = formula(alias_path: alias_path) { url "foo-#{version}" }
+    f.build = tab
+    f
+  end
+
+  def setup
+    alias_name = "bar"
+    @alias_path = "#{CoreTap.instance.alias_dir}/#{alias_name}"
+
+    @tab = Tab.empty
+
+    @f = make_formula("1.0")
+    @new_formula = make_formula("1.1")
+
+    Formula.stubs(:installed).returns([f])
+  end
+
+  def test_alias_changes_when_not_installed_with_alias
+    tab.source["path"] = Formulary.core_path(f.name).to_s
+
+    assert_nil f.current_installed_alias_target
+    assert_equal f, f.latest_formula
+    refute_predicate f, :installed_alias_target_changed?
+    refute_predicate f, :supersedes_an_installed_formula?
+    refute_predicate f, :alias_changed?
+    assert_predicate f.old_installed_formulae, :empty?
+  end
+
+  def test_alias_changes_when_not_changed
+    tab.source["path"] = alias_path
+    stub_formula_loader(f, alias_path)
+
+    assert_equal f, f.current_installed_alias_target
+    assert_equal f, f.latest_formula
+    refute_predicate f, :installed_alias_target_changed?
+    refute_predicate f, :supersedes_an_installed_formula?
+    refute_predicate f, :alias_changed?
+    assert_predicate f.old_installed_formulae, :empty?
+  end
+
+  def test_alias_changes_when_new_alias_target
+    tab.source["path"] = alias_path
+    stub_formula_loader(new_formula, alias_path)
+
+    assert_equal new_formula, f.current_installed_alias_target
+    assert_equal new_formula, f.latest_formula
+    assert_predicate f, :installed_alias_target_changed?
+    refute_predicate f, :supersedes_an_installed_formula?
+    assert_predicate f, :alias_changed?
+    assert_predicate f.old_installed_formulae, :empty?
+  end
+
+  def test_alias_changes_when_old_formulae_installed
+    tab.source["path"] = alias_path
+    stub_formula_loader(new_formula, alias_path)
+
+    assert_equal new_formula, new_formula.current_installed_alias_target
+    assert_equal new_formula, new_formula.latest_formula
+    refute_predicate new_formula, :installed_alias_target_changed?
+    assert_predicate new_formula, :supersedes_an_installed_formula?
+    assert_predicate new_formula, :alias_changed?
+    assert_equal [f], new_formula.old_installed_formulae
+  end
+end
+
 class OutdatedVersionsTests < Homebrew::TestCase
-  attr_reader :outdated_prefix, :same_prefix, :greater_prefix, :head_prefix
-  attr_reader :f
+  attr_reader :outdated_prefix,
+              :same_prefix,
+              :greater_prefix,
+              :head_prefix,
+              :old_alias_target_prefix
+  attr_reader :f, :old_formula, :new_formula
 
   def setup
     @f = formula do
       url "foo"
       version "1.20"
     end
+
+    @old_formula = formula("foo@1") { url "foo-1.0" }
+    @new_formula = formula("foo@2") { url "foo-2.0" }
+
     @outdated_prefix = HOMEBREW_CELLAR/"#{f.name}/1.11"
     @same_prefix = HOMEBREW_CELLAR/"#{f.name}/1.20"
     @greater_prefix = HOMEBREW_CELLAR/"#{f.name}/1.21"
     @head_prefix = HOMEBREW_CELLAR/"#{f.name}/HEAD"
+    @old_alias_target_prefix = HOMEBREW_CELLAR/"#{old_formula.name}/1.0"
   end
 
   def teardown
-    @f.rack.rmtree if @f.rack.exist?
+    formulae = [@f, @old_formula, @new_formula]
+    formulae.map(&:rack).select(&:exist?).each(&:rmtree)
+  end
+
+  def alias_path
+    "#{@f.tap.alias_dir}/bar"
   end
 
   def setup_tab_for_prefix(prefix, options = {})
     prefix.mkpath
     tab = Tab.empty
     tab.tabfile = prefix.join("INSTALL_RECEIPT.json")
+    tab.source["path"] = options[:path].to_s if options[:path]
     tab.source["tap"] = options[:tap] if options[:tap]
     tab.source["versions"] = options[:versions] if options[:versions]
     tab.source_modified_time = options[:source_modified_time].to_i
@@ -611,96 +889,148 @@ class OutdatedVersionsTests < Homebrew::TestCase
     tab
   end
 
-  def reset_outdated_versions
-    f.instance_variable_set(:@outdated_versions, nil)
+  def reset_outdated_kegs
+    f.instance_variable_set(:@outdated_kegs, nil)
   end
 
   def test_greater_different_tap_installed
     setup_tab_for_prefix(greater_prefix, tap: "user/repo")
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
   end
 
   def test_greater_same_tap_installed
     f.instance_variable_set(:@tap, CoreTap.instance)
     setup_tab_for_prefix(greater_prefix, tap: "homebrew/core")
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
   end
 
   def test_outdated_different_tap_installed
     setup_tab_for_prefix(outdated_prefix, tap: "user/repo")
-    refute_predicate f.outdated_versions, :empty?
+    refute_predicate f.outdated_kegs, :empty?
   end
 
   def test_outdated_same_tap_installed
     f.instance_variable_set(:@tap, CoreTap.instance)
     setup_tab_for_prefix(outdated_prefix, tap: "homebrew/core")
-    refute_predicate f.outdated_versions, :empty?
+    refute_predicate f.outdated_kegs, :empty?
+  end
+
+  def test_outdated_follow_alias_and_alias_unchanged
+    f.follow_installed_alias = true
+    f.build = setup_tab_for_prefix(same_prefix, path: alias_path)
+    stub_formula_loader(f, alias_path)
+    assert_predicate f.outdated_kegs, :empty?
+  end
+
+  def test_outdated_follow_alias_and_alias_changed_and_new_target_not_installed
+    f.follow_installed_alias = true
+    f.build = setup_tab_for_prefix(same_prefix, path: alias_path)
+    stub_formula_loader(new_formula, alias_path)
+    refute_predicate f.outdated_kegs, :empty?
+  end
+
+  def test_outdated_follow_alias_and_alias_changed_and_new_target_installed
+    f.follow_installed_alias = true
+    f.build = setup_tab_for_prefix(same_prefix, path: alias_path)
+    stub_formula_loader(new_formula, alias_path)
+    setup_tab_for_prefix(new_formula.prefix) # install new_formula
+    assert_predicate f.outdated_kegs, :empty?
+  end
+
+  def test_outdated_no_follow_alias_and_alias_unchanged
+    f.follow_installed_alias = false
+    f.build = setup_tab_for_prefix(same_prefix, path: alias_path)
+    stub_formula_loader(f, alias_path)
+    assert_predicate f.outdated_kegs, :empty?
+  end
+
+  def test_outdated_no_follow_alias_and_alias_changed
+    f.follow_installed_alias = false
+    f.build = setup_tab_for_prefix(same_prefix, path: alias_path)
+    stub_formula_loader(formula("foo@2") { url "foo-2.0" }, alias_path)
+    assert_predicate f.outdated_kegs, :empty?
+  end
+
+  def test_outdated_old_alias_targets_installed
+    @f = formula(alias_path: alias_path) { url "foo-1.0" }
+    tab = setup_tab_for_prefix(old_alias_target_prefix, path: alias_path)
+    old_formula.build = tab
+    Formula.stubs(:installed).returns([old_formula])
+    refute_predicate f.outdated_kegs, :empty?
+  end
+
+  def test_outdated_old_alias_targets_not_installed
+    @f = formula(alias_path: alias_path) { url "foo-1.0" }
+    tab = setup_tab_for_prefix(old_alias_target_prefix, path: old_formula.path)
+    old_formula.build = tab
+    Formula.stubs(:installed).returns([old_formula])
+    assert_predicate f.outdated_kegs, :empty?
   end
 
-  def test_same_head_installed
+  def test_outdated_same_head_installed
     f.instance_variable_set(:@tap, CoreTap.instance)
     setup_tab_for_prefix(head_prefix, tap: "homebrew/core")
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
   end
 
-  def test_different_head_installed
+  def test_outdated_different_head_installed
     f.instance_variable_set(:@tap, CoreTap.instance)
     setup_tab_for_prefix(head_prefix, tap: "user/repo")
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
   end
 
-  def test_mixed_taps_greater_version_installed
+  def test_outdated_mixed_taps_greater_version_installed
     f.instance_variable_set(:@tap, CoreTap.instance)
     setup_tab_for_prefix(outdated_prefix, tap: "homebrew/core")
     setup_tab_for_prefix(greater_prefix, tap: "user/repo")
 
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
 
     setup_tab_for_prefix(greater_prefix, tap: "homebrew/core")
-    reset_outdated_versions
+    reset_outdated_kegs
 
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
   end
 
-  def test_mixed_taps_outdated_version_installed
+  def test_outdated_mixed_taps_outdated_version_installed
     f.instance_variable_set(:@tap, CoreTap.instance)
 
     extra_outdated_prefix = HOMEBREW_CELLAR/"#{f.name}/1.0"
 
     setup_tab_for_prefix(outdated_prefix)
     setup_tab_for_prefix(extra_outdated_prefix, tap: "homebrew/core")
-    reset_outdated_versions
+    reset_outdated_kegs
 
-    refute_predicate f.outdated_versions, :empty?
+    refute_predicate f.outdated_kegs, :empty?
 
     setup_tab_for_prefix(outdated_prefix, tap: "user/repo")
-    reset_outdated_versions
+    reset_outdated_kegs
 
-    refute_predicate f.outdated_versions, :empty?
+    refute_predicate f.outdated_kegs, :empty?
   end
 
-  def test_same_version_tap_installed
+  def test_outdated_same_version_tap_installed
     f.instance_variable_set(:@tap, CoreTap.instance)
     setup_tab_for_prefix(same_prefix, tap: "homebrew/core")
 
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
 
     setup_tab_for_prefix(same_prefix, tap: "user/repo")
-    reset_outdated_versions
+    reset_outdated_kegs
 
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
   end
 
   def test_outdated_installed_head_less_than_stable
     tab = setup_tab_for_prefix(head_prefix, versions: { "stable" => "1.0" })
-    refute_predicate f.outdated_versions, :empty?
+    refute_predicate f.outdated_kegs, :empty?
 
     # Tab.for_keg(head_prefix) will be fetched from CACHE but we write it anyway
     tab.source["versions"] = { "stable" => f.version.to_s }
     tab.write
-    reset_outdated_versions
+    reset_outdated_kegs
 
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
   end
 
   def test_outdated_fetch_head
@@ -738,20 +1068,20 @@ class OutdatedVersionsTests < Homebrew::TestCase
       end
     end
 
-    refute_predicate f.outdated_versions(fetch_head: true), :empty?
+    refute_predicate f.outdated_kegs(fetch_head: true), :empty?
 
     tab_a.source["versions"] = { "stable" => f.version.to_s }
     tab_a.write
-    reset_outdated_versions
-    refute_predicate f.outdated_versions(fetch_head: true), :empty?
+    reset_outdated_kegs
+    refute_predicate f.outdated_kegs(fetch_head: true), :empty?
 
     head_prefix_a.rmtree
-    reset_outdated_versions
-    refute_predicate f.outdated_versions(fetch_head: true), :empty?
+    reset_outdated_kegs
+    refute_predicate f.outdated_kegs(fetch_head: true), :empty?
 
     setup_tab_for_prefix(head_prefix_c, source_modified_time: 1)
-    reset_outdated_versions
-    assert_predicate f.outdated_versions(fetch_head: true), :empty?
+    reset_outdated_kegs
+    assert_predicate f.outdated_kegs(fetch_head: true), :empty?
   ensure
     ENV.replace(initial_env)
     testball_repo.rmtree if testball_repo.exist?
@@ -762,7 +1092,7 @@ class OutdatedVersionsTests < Homebrew::TestCase
     FileUtils.rm_rf HOMEBREW_CELLAR/"testball"
   end
 
-  def test_outdated_versions_version_scheme_changed
+  def test_outdated_kegs_version_scheme_changed
     @f = formula("testball") do
       url "foo"
       version "20141010"
@@ -772,12 +1102,12 @@ class OutdatedVersionsTests < Homebrew::TestCase
     prefix = HOMEBREW_CELLAR.join("testball/0.1")
     setup_tab_for_prefix(prefix, versions: { "stable" => "0.1" })
 
-    refute_predicate f.outdated_versions, :empty?
+    refute_predicate f.outdated_kegs, :empty?
   ensure
     prefix.rmtree
   end
 
-  def test_outdated_versions_mixed_version_schemes
+  def test_outdated_kegs_mixed_version_schemes
     @f = formula("testball") do
       url "foo"
       version "20141010"
@@ -790,23 +1120,23 @@ class OutdatedVersionsTests < Homebrew::TestCase
     prefix_b = HOMEBREW_CELLAR.join("testball/2.14")
     setup_tab_for_prefix(prefix_b, versions: { "stable" => "2.14", "version_scheme" => 2 })
 
-    refute_predicate f.outdated_versions, :empty?
-    reset_outdated_versions
+    refute_predicate f.outdated_kegs, :empty?
+    reset_outdated_kegs
 
     prefix_c = HOMEBREW_CELLAR.join("testball/20141009")
     setup_tab_for_prefix(prefix_c, versions: { "stable" => "20141009", "version_scheme" => 3 })
 
-    refute_predicate f.outdated_versions, :empty?
-    reset_outdated_versions
+    refute_predicate f.outdated_kegs, :empty?
+    reset_outdated_kegs
 
     prefix_d = HOMEBREW_CELLAR.join("testball/20141011")
     setup_tab_for_prefix(prefix_d, versions: { "stable" => "20141009", "version_scheme" => 3 })
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
   ensure
     f.rack.rmtree
   end
 
-  def test_outdated_versions_head_with_version_scheme
+  def test_outdated_kegs_head_with_version_scheme
     @f = formula("testball") do
       url "foo"
       version "1.0"
@@ -816,13 +1146,13 @@ class OutdatedVersionsTests < Homebrew::TestCase
     head_prefix = HOMEBREW_CELLAR.join("testball/HEAD")
 
     setup_tab_for_prefix(head_prefix, versions: { "stable" => "1.0", "version_scheme" => 1 })
-    refute_predicate f.outdated_versions, :empty?
+    refute_predicate f.outdated_kegs, :empty?
 
-    reset_outdated_versions
+    reset_outdated_kegs
     head_prefix.rmtree
 
     setup_tab_for_prefix(head_prefix, versions: { "stable" => "1.0", "version_scheme" => 2 })
-    assert_predicate f.outdated_versions, :empty?
+    assert_predicate f.outdated_kegs, :empty?
   ensure
     head_prefix.rmtree
   end
diff --git a/Library/Homebrew/test/test_formulary.rb b/Library/Homebrew/test/test_formulary.rb
index 8b3417dad..c545ff84d 100644
--- a/Library/Homebrew/test/test_formulary.rb
+++ b/Library/Homebrew/test/test_formulary.rb
@@ -89,7 +89,7 @@ class FormularyFactoryTest < Homebrew::TestCase
     FileUtils.ln_s @path, alias_path
     result = Formulary.factory("foo")
     assert_kind_of Formula, result
-    assert_equal alias_path, result.alias_path
+    assert_equal alias_path.to_s, result.alias_path
   ensure
     alias_dir.rmtree
   end
diff --git a/Library/Homebrew/test/testing_env.rb b/Library/Homebrew/test/testing_env.rb
index cbbc5eff1..aa89ba2bd 100644
--- a/Library/Homebrew/test/testing_env.rb
+++ b/Library/Homebrew/test/testing_env.rb
@@ -121,5 +121,13 @@ module Homebrew
         ENV.replace old
       end
     end
+
+    # Use a stubbed {Formulary::FormulaLoader} to make a given formula be found
+    # when loading from {Formulary} with `ref`.
+    def stub_formula_loader(formula, ref = formula.name)
+      loader = mock
+      loader.stubs(:get_formula).returns(formula)
+      Formulary.stubs(:loader_for).with(ref).returns(loader)
+    end
   end
 end