diff --git a/Library/Homebrew/.rubocop_todo.yml b/Library/Homebrew/.rubocop_todo.yml
index 4c6a4bbc55..6a31cdecd1 100644
--- a/Library/Homebrew/.rubocop_todo.yml
+++ b/Library/Homebrew/.rubocop_todo.yml
@@ -66,7 +66,7 @@ Metrics/BlockNesting:
 # Offense count: 19
 # Configuration parameters: CountComments.
 Metrics/ModuleLength:
-  Max: 366
+  Max: 400
 
 # Offense count: 2
 # Configuration parameters: CountKeywordArgs.
diff --git a/Library/Homebrew/build_environment.rb b/Library/Homebrew/build_environment.rb
index b66aafcdf7..e3299fb943 100644
--- a/Library/Homebrew/build_environment.rb
+++ b/Library/Homebrew/build_environment.rb
@@ -32,6 +32,8 @@ module BuildEnvironmentDSL
 end
 
 module Homebrew
+  module_function
+
   def build_env_keys(env)
     %w[
       CC CXX LD OBJC OBJCXX
diff --git a/Library/Homebrew/cmd/--cache.rb b/Library/Homebrew/cmd/--cache.rb
index d73d0cce10..2c407cefe0 100644
--- a/Library/Homebrew/cmd/--cache.rb
+++ b/Library/Homebrew/cmd/--cache.rb
@@ -7,6 +7,8 @@
 require "cmd/fetch"
 
 module Homebrew
+  module_function
+
   def __cache
     if ARGV.named.empty?
       puts HOMEBREW_CACHE
diff --git a/Library/Homebrew/cmd/--cellar.rb b/Library/Homebrew/cmd/--cellar.rb
index e1c641ce1b..f35847ead6 100644
--- a/Library/Homebrew/cmd/--cellar.rb
+++ b/Library/Homebrew/cmd/--cellar.rb
@@ -7,6 +7,8 @@
 #:    without any sort of versioned directory as the last path.
 
 module Homebrew
+  module_function
+
   def __cellar
     if ARGV.named.empty?
       puts HOMEBREW_CELLAR
diff --git a/Library/Homebrew/cmd/--env.rb b/Library/Homebrew/cmd/--env.rb
index 0feb338dc8..323964dad0 100644
--- a/Library/Homebrew/cmd/--env.rb
+++ b/Library/Homebrew/cmd/--env.rb
@@ -6,6 +6,8 @@ require "build_environment"
 require "utils/shell"
 
 module Homebrew
+  module_function
+
   def __env
     ENV.activate_extensions!
     ENV.deps = ARGV.formulae if superenv?
diff --git a/Library/Homebrew/cmd/--prefix.rb b/Library/Homebrew/cmd/--prefix.rb
index 07b43693c6..c59830833b 100644
--- a/Library/Homebrew/cmd/--prefix.rb
+++ b/Library/Homebrew/cmd/--prefix.rb
@@ -5,6 +5,8 @@
 #:    Display the location in the cellar where <formula> is or would be installed.
 
 module Homebrew
+  module_function
+
   def __prefix
     if ARGV.named.empty?
       puts HOMEBREW_PREFIX
diff --git a/Library/Homebrew/cmd/--repository.rb b/Library/Homebrew/cmd/--repository.rb
index b3ad8367a4..7a25aba1c1 100644
--- a/Library/Homebrew/cmd/--repository.rb
+++ b/Library/Homebrew/cmd/--repository.rb
@@ -8,6 +8,8 @@
 require "tap"
 
 module Homebrew
+  module_function
+
   def __repository
     if ARGV.named.empty?
       puts HOMEBREW_REPOSITORY
diff --git a/Library/Homebrew/cmd/--version.rb b/Library/Homebrew/cmd/--version.rb
index 9a571abe17..736048341c 100644
--- a/Library/Homebrew/cmd/--version.rb
+++ b/Library/Homebrew/cmd/--version.rb
@@ -2,6 +2,8 @@
 #:    Print the version number of Homebrew to standard output and exit.
 
 module Homebrew
+  module_function
+
   def __version
     # As a special case, `--version` is implemented directly in `brew.rb`. This
     # file merely serves as a container for the documentation. It also catches
diff --git a/Library/Homebrew/cmd/analytics.rb b/Library/Homebrew/cmd/analytics.rb
index 649c537107..2efa5a2d23 100644
--- a/Library/Homebrew/cmd/analytics.rb
+++ b/Library/Homebrew/cmd/analytics.rb
@@ -9,6 +9,8 @@
 #:    Regenerate UUID used in Homebrew's analytics.
 
 module Homebrew
+  module_function
+
   def analytics
     config_file = HOMEBREW_REPOSITORY/".git/config"
 
diff --git a/Library/Homebrew/cmd/cat.rb b/Library/Homebrew/cmd/cat.rb
index a2fbd2f00e..7439869d30 100644
--- a/Library/Homebrew/cmd/cat.rb
+++ b/Library/Homebrew/cmd/cat.rb
@@ -2,6 +2,8 @@
 #:    Display the source to <formula>.
 
 module Homebrew
+  module_function
+
   def cat
     # do not "fix" this to support multiple arguments, the output would be
     # unparsable, if the user wants to cat multiple formula they can call
diff --git a/Library/Homebrew/cmd/cleanup.rb b/Library/Homebrew/cmd/cleanup.rb
index 6e0915c9a8..5b46e08724 100644
--- a/Library/Homebrew/cmd/cleanup.rb
+++ b/Library/Homebrew/cmd/cleanup.rb
@@ -15,6 +15,8 @@ require "cleanup"
 require "utils"
 
 module Homebrew
+  module_function
+
   def cleanup
     if ARGV.named.empty?
       Cleanup.cleanup
diff --git a/Library/Homebrew/cmd/command.rb b/Library/Homebrew/cmd/command.rb
index b76468f621..39e8ba6fc4 100644
--- a/Library/Homebrew/cmd/command.rb
+++ b/Library/Homebrew/cmd/command.rb
@@ -4,6 +4,8 @@
 require "commands"
 
 module Homebrew
+  module_function
+
   def command
     abort "This command requires a command argument" if ARGV.empty?
     cmd = ARGV.first
diff --git a/Library/Homebrew/cmd/commands.rb b/Library/Homebrew/cmd/commands.rb
index 4fad764ca6..f6445d560c 100644
--- a/Library/Homebrew/cmd/commands.rb
+++ b/Library/Homebrew/cmd/commands.rb
@@ -5,6 +5,8 @@
 #:    With `--include-aliases`, the aliases of internal commands will be included.
 
 module Homebrew
+  module_function
+
   def commands
     if ARGV.include? "--quiet"
       cmds = internal_commands + external_commands
@@ -48,8 +50,6 @@ module Homebrew
     end.sort
   end
 
-  private
-
   def find_internal_commands(directory)
     directory.children.each_with_object([]) do |f, cmds|
       cmds << f.basename.to_s.sub(/\.(?:rb|sh)$/, "") if f.file?
diff --git a/Library/Homebrew/cmd/config.rb b/Library/Homebrew/cmd/config.rb
index b5f2502b03..daaa51f32b 100644
--- a/Library/Homebrew/cmd/config.rb
+++ b/Library/Homebrew/cmd/config.rb
@@ -6,6 +6,8 @@
 require "system_config"
 
 module Homebrew
+  module_function
+
   def config
     SystemConfig.dump_verbose_config
   end
diff --git a/Library/Homebrew/cmd/deps.rb b/Library/Homebrew/cmd/deps.rb
index acaf922d7b..a5089392fc 100644
--- a/Library/Homebrew/cmd/deps.rb
+++ b/Library/Homebrew/cmd/deps.rb
@@ -42,6 +42,8 @@ require "formula"
 require "ostruct"
 
 module Homebrew
+  module_function
+
   def deps
     mode = OpenStruct.new(
       installed?: ARGV.include?("--installed"),
diff --git a/Library/Homebrew/cmd/desc.rb b/Library/Homebrew/cmd/desc.rb
index 9bb737e40a..3ef02288bd 100644
--- a/Library/Homebrew/cmd/desc.rb
+++ b/Library/Homebrew/cmd/desc.rb
@@ -12,6 +12,8 @@ require "descriptions"
 require "cmd/search"
 
 module Homebrew
+  module_function
+
   def desc
     search_type = []
     search_type << :either if ARGV.flag? "--search"
diff --git a/Library/Homebrew/cmd/diy.rb b/Library/Homebrew/cmd/diy.rb
index 95ec7fe35b..a8f6440df6 100644
--- a/Library/Homebrew/cmd/diy.rb
+++ b/Library/Homebrew/cmd/diy.rb
@@ -11,6 +11,8 @@
 require "formula"
 
 module Homebrew
+  module_function
+
   def diy
     path = Pathname.getwd
 
diff --git a/Library/Homebrew/cmd/doctor.rb b/Library/Homebrew/cmd/doctor.rb
index 0fcd3a74df..cca2dca032 100644
--- a/Library/Homebrew/cmd/doctor.rb
+++ b/Library/Homebrew/cmd/doctor.rb
@@ -8,6 +8,8 @@
 require "diagnostic"
 
 module Homebrew
+  module_function
+
   def doctor
     inject_dump_stats!(Diagnostic::Checks, /^check_*/) if ARGV.switch? "D"
 
diff --git a/Library/Homebrew/cmd/fetch.rb b/Library/Homebrew/cmd/fetch.rb
index 9c42eda236..f92ef03b23 100644
--- a/Library/Homebrew/cmd/fetch.rb
+++ b/Library/Homebrew/cmd/fetch.rb
@@ -24,6 +24,8 @@
 require "formula"
 
 module Homebrew
+  module_function
+
   def fetch
     raise FormulaUnspecifiedError if ARGV.named.empty?
 
@@ -93,8 +95,6 @@ module Homebrew
     opoo "Patch reports different #{e.hash_type}: #{e.expected}"
   end
 
-  private
-
   def retry_fetch?(f)
     @fetch_failed ||= Set.new
     if ARGV.include?("--retry") && @fetch_failed.add?(f)
diff --git a/Library/Homebrew/cmd/gist-logs.rb b/Library/Homebrew/cmd/gist-logs.rb
index 200ad9fb5e..e55eefc170 100644
--- a/Library/Homebrew/cmd/gist-logs.rb
+++ b/Library/Homebrew/cmd/gist-logs.rb
@@ -15,6 +15,8 @@ require "stringio"
 require "socket"
 
 module Homebrew
+  module_function
+
   def gistify_logs(f)
     files = load_logs(f.logs)
     build_time = f.logs.ctime
diff --git a/Library/Homebrew/cmd/help.rb b/Library/Homebrew/cmd/help.rb
index bfcb6838d7..982e249655 100644
--- a/Library/Homebrew/cmd/help.rb
+++ b/Library/Homebrew/cmd/help.rb
@@ -34,6 +34,8 @@ EOS
 require "commands"
 
 module Homebrew
+  module_function
+
   def help(cmd = nil, flags = {})
     # Resolve command aliases and find file containing the implementation.
     if cmd
@@ -71,8 +73,6 @@ module Homebrew
     exit 0
   end
 
-  private
-
   def command_help(path)
     help_lines = path.read.lines.grep(/^#:/)
     if help_lines.empty?
diff --git a/Library/Homebrew/cmd/home.rb b/Library/Homebrew/cmd/home.rb
index 0c3009545c..50f3936e8c 100644
--- a/Library/Homebrew/cmd/home.rb
+++ b/Library/Homebrew/cmd/home.rb
@@ -5,6 +5,8 @@
 #:    Open <formula>'s homepage in a browser.
 
 module Homebrew
+  module_function
+
   def home
     if ARGV.named.empty?
       exec_browser HOMEBREW_WWW
diff --git a/Library/Homebrew/cmd/info.rb b/Library/Homebrew/cmd/info.rb
index 2cfb89ea55..fefabf85f4 100644
--- a/Library/Homebrew/cmd/info.rb
+++ b/Library/Homebrew/cmd/info.rb
@@ -25,6 +25,8 @@ require "tab"
 require "utils/json"
 
 module Homebrew
+  module_function
+
   def info
     # eventually we'll solidify an API, but we'll keep old versions
     # awhile around for compatibility
diff --git a/Library/Homebrew/cmd/install.rb b/Library/Homebrew/cmd/install.rb
index 402a159db1..ffb7eeab3d 100644
--- a/Library/Homebrew/cmd/install.rb
+++ b/Library/Homebrew/cmd/install.rb
@@ -64,6 +64,8 @@ require "hardware"
 require "development_tools"
 
 module Homebrew
+  module_function
+
   def install
     raise FormulaUnspecifiedError if ARGV.named.empty?
 
diff --git a/Library/Homebrew/cmd/irb.rb b/Library/Homebrew/cmd/irb.rb
index 1db0855bbf..d162e3f4a5 100644
--- a/Library/Homebrew/cmd/irb.rb
+++ b/Library/Homebrew/cmd/irb.rb
@@ -19,6 +19,8 @@ class String
 end
 
 module Homebrew
+  module_function
+
   def irb
     if ARGV.include? "--examples"
       puts "'v8'.f # => instance of the v8 formula"
diff --git a/Library/Homebrew/cmd/leaves.rb b/Library/Homebrew/cmd/leaves.rb
index 37e379d49e..4038aee4c3 100644
--- a/Library/Homebrew/cmd/leaves.rb
+++ b/Library/Homebrew/cmd/leaves.rb
@@ -6,6 +6,8 @@ require "tab"
 require "set"
 
 module Homebrew
+  module_function
+
   def leaves
     installed = Formula.installed
     deps_of_installed = Set.new
diff --git a/Library/Homebrew/cmd/link.rb b/Library/Homebrew/cmd/link.rb
index 6486e6f185..98cf98bf77 100644
--- a/Library/Homebrew/cmd/link.rb
+++ b/Library/Homebrew/cmd/link.rb
@@ -15,6 +15,8 @@
 require "ostruct"
 
 module Homebrew
+  module_function
+
   def link
     raise KegUnspecifiedError if ARGV.named.empty?
 
@@ -71,8 +73,6 @@ module Homebrew
     end
   end
 
-  private
-
   def keg_only?(rack)
     Formulary.from_rack(rack).keg_only?
   rescue FormulaUnavailableError, TapFormulaAmbiguityError, TapFormulaWithOldnameAmbiguityError
diff --git a/Library/Homebrew/cmd/linkapps.rb b/Library/Homebrew/cmd/linkapps.rb
index c7685855f3..bd88409aaa 100644
--- a/Library/Homebrew/cmd/linkapps.rb
+++ b/Library/Homebrew/cmd/linkapps.rb
@@ -11,6 +11,8 @@ require "keg"
 require "formula"
 
 module Homebrew
+  module_function
+
   def linkapps
     target_dir = linkapps_target(local: ARGV.include?("--local"))
 
@@ -55,8 +57,6 @@ module Homebrew
     end
   end
 
-  private
-
   def linkapps_target(opts = {})
     local = opts.fetch(:local, false)
     Pathname.new(local ? "~/Applications" : "/Applications").expand_path
diff --git a/Library/Homebrew/cmd/list.rb b/Library/Homebrew/cmd/list.rb
index 43a03829e0..01af678a71 100644
--- a/Library/Homebrew/cmd/list.rb
+++ b/Library/Homebrew/cmd/list.rb
@@ -22,6 +22,8 @@ require "metafiles"
 require "formula"
 
 module Homebrew
+  module_function
+
   def list
     # Use of exec means we don't explicitly exit
     list_unbrewed if ARGV.flag? "--unbrewed"
@@ -58,8 +60,6 @@ module Homebrew
     end
   end
 
-  private
-
   UNBREWED_EXCLUDE_FILES = %w[.DS_Store].freeze
   UNBREWED_EXCLUDE_PATHS = %w[
     .github/*
diff --git a/Library/Homebrew/cmd/log.rb b/Library/Homebrew/cmd/log.rb
index 9492c1e1ed..81f972b028 100644
--- a/Library/Homebrew/cmd/log.rb
+++ b/Library/Homebrew/cmd/log.rb
@@ -5,6 +5,8 @@
 require "formula"
 
 module Homebrew
+  module_function
+
   def log
     if ARGV.named.empty?
       cd HOMEBREW_REPOSITORY
@@ -16,8 +18,6 @@ module Homebrew
     end
   end
 
-  private
-
   def git_log(path = nil)
     if File.exist? "#{`git rev-parse --show-toplevel`.chomp}/.git/shallow"
       opoo <<-EOS.undent
diff --git a/Library/Homebrew/cmd/migrate.rb b/Library/Homebrew/cmd/migrate.rb
index 27ca5261f9..2726b14800 100644
--- a/Library/Homebrew/cmd/migrate.rb
+++ b/Library/Homebrew/cmd/migrate.rb
@@ -8,6 +8,8 @@
 require "migrator"
 
 module Homebrew
+  module_function
+
   def migrate
     raise FormulaUnspecifiedError if ARGV.named.empty?
 
diff --git a/Library/Homebrew/cmd/missing.rb b/Library/Homebrew/cmd/missing.rb
index bbd514223f..525461108b 100644
--- a/Library/Homebrew/cmd/missing.rb
+++ b/Library/Homebrew/cmd/missing.rb
@@ -7,6 +7,8 @@ require "tab"
 require "diagnostic"
 
 module Homebrew
+  module_function
+
   def missing
     return unless HOMEBREW_CELLAR.exist?
 
diff --git a/Library/Homebrew/cmd/options.rb b/Library/Homebrew/cmd/options.rb
index 690acd0169..843d3a1ee8 100644
--- a/Library/Homebrew/cmd/options.rb
+++ b/Library/Homebrew/cmd/options.rb
@@ -12,6 +12,8 @@ require "formula"
 require "options"
 
 module Homebrew
+  module_function
+
   def options
     if ARGV.include? "--all"
       puts_options Formula.to_a
diff --git a/Library/Homebrew/cmd/outdated.rb b/Library/Homebrew/cmd/outdated.rb
index a6fa1f0036..5dc77857ea 100644
--- a/Library/Homebrew/cmd/outdated.rb
+++ b/Library/Homebrew/cmd/outdated.rb
@@ -21,6 +21,8 @@ require "formula"
 require "keg"
 
 module Homebrew
+  module_function
+
   def outdated
     formulae = if ARGV.resolved_formulae.empty?
       Formula.installed
diff --git a/Library/Homebrew/cmd/pin.rb b/Library/Homebrew/cmd/pin.rb
index a54ef6e7bf..c5087f6d4c 100644
--- a/Library/Homebrew/cmd/pin.rb
+++ b/Library/Homebrew/cmd/pin.rb
@@ -5,6 +5,8 @@
 require "formula"
 
 module Homebrew
+  module_function
+
   def pin
     raise FormulaUnspecifiedError if ARGV.named.empty?
 
diff --git a/Library/Homebrew/cmd/postinstall.rb b/Library/Homebrew/cmd/postinstall.rb
index e0bd8e31b1..1e205e65de 100644
--- a/Library/Homebrew/cmd/postinstall.rb
+++ b/Library/Homebrew/cmd/postinstall.rb
@@ -4,6 +4,8 @@
 require "sandbox"
 
 module Homebrew
+  module_function
+
   def postinstall
     ARGV.resolved_formulae.each { |f| run_post_install(f) if f.post_install_defined? }
   end
diff --git a/Library/Homebrew/cmd/prune.rb b/Library/Homebrew/cmd/prune.rb
index 83979064a1..e2e6d77b8e 100644
--- a/Library/Homebrew/cmd/prune.rb
+++ b/Library/Homebrew/cmd/prune.rb
@@ -12,6 +12,8 @@ require "cmd/tap"
 require "cmd/unlinkapps"
 
 module Homebrew
+  module_function
+
   def prune
     ObserverPathnameExtension.reset_counts!
 
diff --git a/Library/Homebrew/cmd/readall.rb b/Library/Homebrew/cmd/readall.rb
index e77e688652..7c1a085c9b 100644
--- a/Library/Homebrew/cmd/readall.rb
+++ b/Library/Homebrew/cmd/readall.rb
@@ -9,6 +9,8 @@
 require "readall"
 
 module Homebrew
+  module_function
+
   def readall
     if ARGV.include?("--syntax")
       ruby_files = []
diff --git a/Library/Homebrew/cmd/reinstall.rb b/Library/Homebrew/cmd/reinstall.rb
index bda6022bfd..618835d744 100644
--- a/Library/Homebrew/cmd/reinstall.rb
+++ b/Library/Homebrew/cmd/reinstall.rb
@@ -5,6 +5,8 @@ require "formula_installer"
 require "development_tools"
 
 module Homebrew
+  module_function
+
   def reinstall
     FormulaInstaller.prevent_build_flags unless DevelopmentTools.installed?
 
diff --git a/Library/Homebrew/cmd/search.rb b/Library/Homebrew/cmd/search.rb
index 5342b23b6e..8d6e5ad7c3 100644
--- a/Library/Homebrew/cmd/search.rb
+++ b/Library/Homebrew/cmd/search.rb
@@ -21,6 +21,8 @@ require "official_taps"
 require "descriptions"
 
 module Homebrew
+  module_function
+
   SEARCH_ERROR_QUEUE = Queue.new
 
   def search
diff --git a/Library/Homebrew/cmd/sh.rb b/Library/Homebrew/cmd/sh.rb
index 11f57b6601..09e7f435e5 100644
--- a/Library/Homebrew/cmd/sh.rb
+++ b/Library/Homebrew/cmd/sh.rb
@@ -9,6 +9,8 @@ require "extend/ENV"
 require "formula"
 
 module Homebrew
+  module_function
+
   def sh
     ENV.activate_extensions!
 
diff --git a/Library/Homebrew/cmd/style.rb b/Library/Homebrew/cmd/style.rb
index e666eb2007..9538b890a9 100644
--- a/Library/Homebrew/cmd/style.rb
+++ b/Library/Homebrew/cmd/style.rb
@@ -17,6 +17,8 @@ require "utils"
 require "utils/json"
 
 module Homebrew
+  module_function
+
   def style
     target = if ARGV.named.empty?
       nil
diff --git a/Library/Homebrew/cmd/switch.rb b/Library/Homebrew/cmd/switch.rb
index a44514880a..6eed1fd966 100644
--- a/Library/Homebrew/cmd/switch.rb
+++ b/Library/Homebrew/cmd/switch.rb
@@ -6,6 +6,8 @@ require "keg"
 require "cmd/link"
 
 module Homebrew
+  module_function
+
   def switch
     if ARGV.named.length != 2
       onoe "Usage: brew switch <name> <version>"
diff --git a/Library/Homebrew/cmd/tap-info.rb b/Library/Homebrew/cmd/tap-info.rb
index 432d512873..f31bf480c8 100644
--- a/Library/Homebrew/cmd/tap-info.rb
+++ b/Library/Homebrew/cmd/tap-info.rb
@@ -18,6 +18,8 @@
 require "tap"
 
 module Homebrew
+  module_function
+
   def tap_info
     if ARGV.include? "--installed"
       taps = Tap
@@ -34,8 +36,6 @@ module Homebrew
     end
   end
 
-  private
-
   def print_tap_info(taps)
     if taps.none?
       tap_count = 0
diff --git a/Library/Homebrew/cmd/tap-pin.rb b/Library/Homebrew/cmd/tap-pin.rb
index 74e9fae3f3..41957f2652 100644
--- a/Library/Homebrew/cmd/tap-pin.rb
+++ b/Library/Homebrew/cmd/tap-pin.rb
@@ -5,6 +5,8 @@
 require "tap"
 
 module Homebrew
+  module_function
+
   def tap_pin
     ARGV.named.each do |name|
       tap = Tap.fetch(name)
diff --git a/Library/Homebrew/cmd/tap-unpin.rb b/Library/Homebrew/cmd/tap-unpin.rb
index 7ea2831f29..05bfc7c8b9 100644
--- a/Library/Homebrew/cmd/tap-unpin.rb
+++ b/Library/Homebrew/cmd/tap-unpin.rb
@@ -4,6 +4,8 @@
 require "tap"
 
 module Homebrew
+  module_function
+
   def tap_unpin
     ARGV.named.each do |name|
       tap = Tap.fetch(name)
diff --git a/Library/Homebrew/cmd/tap.rb b/Library/Homebrew/cmd/tap.rb
index 8ad63e4ba8..5b4ed24759 100644
--- a/Library/Homebrew/cmd/tap.rb
+++ b/Library/Homebrew/cmd/tap.rb
@@ -34,6 +34,8 @@
 require "tap"
 
 module Homebrew
+  module_function
+
   def tap
     if ARGV.include? "--repair"
       Tap.each(&:link_manpages)
diff --git a/Library/Homebrew/cmd/uninstall.rb b/Library/Homebrew/cmd/uninstall.rb
index f4ca8ff87f..8bcfc31fbb 100644
--- a/Library/Homebrew/cmd/uninstall.rb
+++ b/Library/Homebrew/cmd/uninstall.rb
@@ -9,6 +9,8 @@ require "formula"
 require "migrator"
 
 module Homebrew
+  module_function
+
   def uninstall
     raise KegUnspecifiedError if ARGV.named.empty?
 
diff --git a/Library/Homebrew/cmd/unlink.rb b/Library/Homebrew/cmd/unlink.rb
index adf0917094..a105f9c56e 100644
--- a/Library/Homebrew/cmd/unlink.rb
+++ b/Library/Homebrew/cmd/unlink.rb
@@ -9,6 +9,8 @@
 require "ostruct"
 
 module Homebrew
+  module_function
+
   def unlink
     raise KegUnspecifiedError if ARGV.named.empty?
 
diff --git a/Library/Homebrew/cmd/unlinkapps.rb b/Library/Homebrew/cmd/unlinkapps.rb
index fc53470ec7..d04ef9ee40 100644
--- a/Library/Homebrew/cmd/unlinkapps.rb
+++ b/Library/Homebrew/cmd/unlinkapps.rb
@@ -12,14 +12,14 @@
 require "cmd/linkapps"
 
 module Homebrew
+  module_function
+
   def unlinkapps
     target_dir = linkapps_target(local: ARGV.include?("--local"))
 
     unlinkapps_from_dir(target_dir, dry_run: ARGV.dry_run?)
   end
 
-  private
-
   def unlinkapps_prune(opts = {})
     opts = opts.merge(prune: true)
     unlinkapps_from_dir(linkapps_target(local: false), opts)
diff --git a/Library/Homebrew/cmd/unpack.rb b/Library/Homebrew/cmd/unpack.rb
index 1a3044c2e6..6f4caea189 100644
--- a/Library/Homebrew/cmd/unpack.rb
+++ b/Library/Homebrew/cmd/unpack.rb
@@ -13,6 +13,8 @@ require "stringio"
 require "formula"
 
 module Homebrew
+  module_function
+
   def unpack
     formulae = ARGV.formulae
     raise FormulaUnspecifiedError if formulae.empty?
diff --git a/Library/Homebrew/cmd/unpin.rb b/Library/Homebrew/cmd/unpin.rb
index 4eb476bdf6..a669df1ec4 100644
--- a/Library/Homebrew/cmd/unpin.rb
+++ b/Library/Homebrew/cmd/unpin.rb
@@ -5,6 +5,8 @@
 require "formula"
 
 module Homebrew
+  module_function
+
   def unpin
     raise FormulaUnspecifiedError if ARGV.named.empty?
 
diff --git a/Library/Homebrew/cmd/untap.rb b/Library/Homebrew/cmd/untap.rb
index be91191b50..0d363b7b58 100644
--- a/Library/Homebrew/cmd/untap.rb
+++ b/Library/Homebrew/cmd/untap.rb
@@ -4,6 +4,8 @@
 require "tap"
 
 module Homebrew
+  module_function
+
   def untap
     raise "Usage is `brew untap <tap-name>`" if ARGV.empty?
 
diff --git a/Library/Homebrew/cmd/update-report.rb b/Library/Homebrew/cmd/update-report.rb
index 357bc3fc15..a76167feb5 100644
--- a/Library/Homebrew/cmd/update-report.rb
+++ b/Library/Homebrew/cmd/update-report.rb
@@ -10,6 +10,8 @@ require "cleanup"
 require "utils"
 
 module Homebrew
+  module_function
+
   def update_preinstall_header
     @header_already_printed ||= begin
       ohai "Auto-updated Homebrew!" if ARGV.include?("--preinstall")
@@ -106,8 +108,6 @@ module Homebrew
     end
   end
 
-  private
-
   def shorten_revision(revision)
     Utils.popen_read("git", "-C", HOMEBREW_REPOSITORY, "rev-parse", "--short", revision).chomp
   end
diff --git a/Library/Homebrew/cmd/upgrade.rb b/Library/Homebrew/cmd/upgrade.rb
index f2c3799aba..40805b4ca6 100644
--- a/Library/Homebrew/cmd/upgrade.rb
+++ b/Library/Homebrew/cmd/upgrade.rb
@@ -18,6 +18,8 @@ require "cleanup"
 require "development_tools"
 
 module Homebrew
+  module_function
+
   def upgrade
     FormulaInstaller.prevent_build_flags unless DevelopmentTools.installed?
 
diff --git a/Library/Homebrew/cmd/uses.rb b/Library/Homebrew/cmd/uses.rb
index 79b57eb235..4acf1b9f1f 100644
--- a/Library/Homebrew/cmd/uses.rb
+++ b/Library/Homebrew/cmd/uses.rb
@@ -23,6 +23,8 @@ require "formula"
 # The intersection is harder to achieve with shell tools.
 
 module Homebrew
+  module_function
+
   def uses
     raise FormulaUnspecifiedError if ARGV.named.empty?
 
diff --git a/Library/Homebrew/compat.rb b/Library/Homebrew/compat.rb
index 98624aebd7..69b45683a0 100644
--- a/Library/Homebrew/compat.rb
+++ b/Library/Homebrew/compat.rb
@@ -2,6 +2,7 @@ require "compat/fails_with_llvm"
 require "compat/tap"
 require "compat/formula"
 require "compat/formula_specialties"
+require "compat/global"
 require "compat/hardware"
 require "compat/macos"
 require "compat/md5"
diff --git a/Library/Homebrew/compat/global.rb b/Library/Homebrew/compat/global.rb
new file mode 100644
index 0000000000..797e9ffe51
--- /dev/null
+++ b/Library/Homebrew/compat/global.rb
@@ -0,0 +1,16 @@
+module Homebrew
+  module_function
+
+  def method_missing(method, *args, &block)
+    if instance_methods.include?(method)
+      # odeprecated "#{self}##{method}", "'module_function' or 'def self.#{method}' to convert it to a class method"
+      return instance_method(method).bind(self).call(*args, &block)
+    end
+    super
+  end
+
+  def respond_to_missing?(method, include_private = false)
+    return true if method_defined?(method)
+    super(method, include_private)
+  end
+end
diff --git a/Library/Homebrew/dev-cmd/aspell-dictionaries.rb b/Library/Homebrew/dev-cmd/aspell-dictionaries.rb
index cbb88ffe56..86ad037ce6 100644
--- a/Library/Homebrew/dev-cmd/aspell-dictionaries.rb
+++ b/Library/Homebrew/dev-cmd/aspell-dictionaries.rb
@@ -7,6 +7,8 @@ require "resource"
 require "formula"
 
 module Homebrew
+  module_function
+
   def aspell_dictionaries
     dict_url    = "http://ftpmirror.gnu.org/aspell/dict"
     dict_mirror = "https://ftp.gnu.org/gnu/aspell/dict"
diff --git a/Library/Homebrew/dev-cmd/audit.rb b/Library/Homebrew/dev-cmd/audit.rb
index 9d7a3ba923..4a86f4c045 100644
--- a/Library/Homebrew/dev-cmd/audit.rb
+++ b/Library/Homebrew/dev-cmd/audit.rb
@@ -37,6 +37,8 @@ require "cmd/style"
 require "date"
 
 module Homebrew
+  module_function
+
   def audit
     Homebrew.inject_dump_stats!(FormulaAuditor, /^audit_/) if ARGV.switch? "D"
 
diff --git a/Library/Homebrew/dev-cmd/boneyard-formula-pr.rb b/Library/Homebrew/dev-cmd/boneyard-formula-pr.rb
index 890c9c4a08..a0739dbe93 100644
--- a/Library/Homebrew/dev-cmd/boneyard-formula-pr.rb
+++ b/Library/Homebrew/dev-cmd/boneyard-formula-pr.rb
@@ -19,6 +19,8 @@ rescue LoadError
 end
 
 module Homebrew
+  module_function
+
   def boneyard_formula_pr
     local_only = ARGV.include?("--local")
     formula = ARGV.formulae.first
diff --git a/Library/Homebrew/dev-cmd/bottle.rb b/Library/Homebrew/dev-cmd/bottle.rb
index b62af1044a..c6a8503b74 100644
--- a/Library/Homebrew/dev-cmd/bottle.rb
+++ b/Library/Homebrew/dev-cmd/bottle.rb
@@ -41,6 +41,8 @@ EOS
 MAXIMUM_STRING_MATCHES = 100
 
 module Homebrew
+  module_function
+
   def keg_contain?(string, keg, ignores)
     @put_string_exists_header, @put_filenames = nil
 
diff --git a/Library/Homebrew/dev-cmd/bump-formula-pr.rb b/Library/Homebrew/dev-cmd/bump-formula-pr.rb
index 31e9cd2c11..32e4b52a2b 100644
--- a/Library/Homebrew/dev-cmd/bump-formula-pr.rb
+++ b/Library/Homebrew/dev-cmd/bump-formula-pr.rb
@@ -35,6 +35,8 @@
 require "formula"
 
 module Homebrew
+  module_function
+
   def inreplace_pairs(path, replacement_pairs)
     if ARGV.dry_run?
       contents = path.open("r") { |f| Formulary.ensure_utf8_encoding(f).read }
diff --git a/Library/Homebrew/dev-cmd/create.rb b/Library/Homebrew/dev-cmd/create.rb
index 19fd251b70..11544dbefe 100644
--- a/Library/Homebrew/dev-cmd/create.rb
+++ b/Library/Homebrew/dev-cmd/create.rb
@@ -24,6 +24,8 @@ require "digest"
 require "erb"
 
 module Homebrew
+  module_function
+
   # Create a formula from a tarball URL
   def create
     # Allow searching MacPorts or Fink.
diff --git a/Library/Homebrew/dev-cmd/edit.rb b/Library/Homebrew/dev-cmd/edit.rb
index 2d2a5ec082..df5bc06058 100644
--- a/Library/Homebrew/dev-cmd/edit.rb
+++ b/Library/Homebrew/dev-cmd/edit.rb
@@ -7,6 +7,8 @@
 require "formula"
 
 module Homebrew
+  module_function
+
   def edit
     unless (HOMEBREW_REPOSITORY/".git").directory?
       raise <<-EOS.undent
diff --git a/Library/Homebrew/dev-cmd/linkage.rb b/Library/Homebrew/dev-cmd/linkage.rb
index 993420c024..44e0f224ee 100644
--- a/Library/Homebrew/dev-cmd/linkage.rb
+++ b/Library/Homebrew/dev-cmd/linkage.rb
@@ -13,6 +13,8 @@
 require "os/mac/linkage_checker"
 
 module Homebrew
+  module_function
+
   def linkage
     ARGV.kegs.each do |keg|
       ohai "Checking #{keg.name} linkage" if ARGV.kegs.size > 1
diff --git a/Library/Homebrew/dev-cmd/man.rb b/Library/Homebrew/dev-cmd/man.rb
index d34d559f76..3395fa673d 100644
--- a/Library/Homebrew/dev-cmd/man.rb
+++ b/Library/Homebrew/dev-cmd/man.rb
@@ -12,6 +12,8 @@ require "erb"
 require "ostruct"
 
 module Homebrew
+  module_function
+
   SOURCE_PATH = HOMEBREW_LIBRARY_PATH/"manpages"
   TARGET_MAN_PATH = HOMEBREW_REPOSITORY/"manpages"
   TARGET_DOC_PATH = HOMEBREW_REPOSITORY/"docs"
@@ -32,8 +34,6 @@ module Homebrew
     end
   end
 
-  private
-
   def regenerate_man_pages
     Homebrew.install_gem_setup_path! "ronn"
 
diff --git a/Library/Homebrew/dev-cmd/mirror.rb b/Library/Homebrew/dev-cmd/mirror.rb
index 9966163f8f..bd5868726f 100644
--- a/Library/Homebrew/dev-cmd/mirror.rb
+++ b/Library/Homebrew/dev-cmd/mirror.rb
@@ -3,6 +3,8 @@
 #:    Reuploads the stable URL for a formula to Bintray to use it as a mirror.
 
 module Homebrew
+  module_function
+
   def mirror
     odie "This command requires at least formula argument!" if ARGV.named.empty?
 
diff --git a/Library/Homebrew/dev-cmd/pull.rb b/Library/Homebrew/dev-cmd/pull.rb
index 857c55993d..7e6e86a850 100644
--- a/Library/Homebrew/dev-cmd/pull.rb
+++ b/Library/Homebrew/dev-cmd/pull.rb
@@ -40,6 +40,8 @@ require "version"
 require "pkg_version"
 
 module Homebrew
+  module_function
+
   def pull
     odie "You meant `git pull --rebase`." if ARGV[0] == "--rebase"
 
@@ -235,8 +237,6 @@ module Homebrew
     str.force_encoding("UTF-8") if str.respond_to?(:force_encoding)
   end
 
-  private
-
   def publish_changed_formula_bottles(_tap, changed_formulae_names)
     if ENV["HOMEBREW_DISABLE_LOAD_FORMULA"]
       raise "Need to load formulae to publish them!"
diff --git a/Library/Homebrew/dev-cmd/tap-readme.rb b/Library/Homebrew/dev-cmd/tap-readme.rb
index e1a3e0eb46..cf5af85ebc 100644
--- a/Library/Homebrew/dev-cmd/tap-readme.rb
+++ b/Library/Homebrew/dev-cmd/tap-readme.rb
@@ -2,6 +2,8 @@
 #:    Generate the README.md file for a new tap.
 
 module Homebrew
+  module_function
+
   def tap_readme
     name = ARGV.first
     raise "A name is required" if name.nil?
diff --git a/Library/Homebrew/dev-cmd/test.rb b/Library/Homebrew/dev-cmd/test.rb
index c20edf804b..4898629b01 100644
--- a/Library/Homebrew/dev-cmd/test.rb
+++ b/Library/Homebrew/dev-cmd/test.rb
@@ -21,6 +21,8 @@ require "sandbox"
 require "timeout"
 
 module Homebrew
+  module_function
+
   def test
     raise FormulaUnspecifiedError if ARGV.named.empty?
 
diff --git a/Library/Homebrew/dev-cmd/tests.rb b/Library/Homebrew/dev-cmd/tests.rb
index 4e2d3b2db8..72f8e0375f 100644
--- a/Library/Homebrew/dev-cmd/tests.rb
+++ b/Library/Homebrew/dev-cmd/tests.rb
@@ -5,6 +5,8 @@ require "fileutils"
 require "tap"
 
 module Homebrew
+  module_function
+
   def tests
     (HOMEBREW_LIBRARY/"Homebrew").cd do
       ENV.delete "HOMEBREW_VERBOSE"
diff --git a/Library/Homebrew/dev-cmd/update-test.rb b/Library/Homebrew/dev-cmd/update-test.rb
index 79b9f621ba..8bb0fa0574 100644
--- a/Library/Homebrew/dev-cmd/update-test.rb
+++ b/Library/Homebrew/dev-cmd/update-test.rb
@@ -15,6 +15,8 @@
 #:    the new repository clone.
 
 module Homebrew
+  module_function
+
   def update_test
     ENV["HOMEBREW_UPDATE_TEST"] = "1"
 
diff --git a/Library/Homebrew/global.rb b/Library/Homebrew/global.rb
index 0cd0d57e67..bf700b0953 100644
--- a/Library/Homebrew/global.rb
+++ b/Library/Homebrew/global.rb
@@ -39,14 +39,21 @@ HOMEBREW_CURL_ARGS = [
 require "tap_constants"
 
 module Homebrew
-  include FileUtils
-  extend self
+  extend FileUtils
 
-  attr_accessor :failed
-  alias failed? failed
+  class << self
+    attr_writer :failed
 
-  attr_accessor :raise_deprecation_exceptions
-  alias raise_deprecation_exceptions? raise_deprecation_exceptions
+    def failed?
+      @failed == true
+    end
+
+    attr_writer :raise_deprecation_exceptions
+
+    def raise_deprecation_exceptions?
+      @raise_deprecation_exceptions == true
+    end
+  end
 end
 
 HOMEBREW_PULL_API_REGEX = %r{https://api\.github\.com/repos/([\w-]+)/([\w-]+)?/pulls/(\d+)}
diff --git a/Library/Homebrew/options.rb b/Library/Homebrew/options.rb
index 08f459b24f..9f12535317 100644
--- a/Library/Homebrew/options.rb
+++ b/Library/Homebrew/options.rb
@@ -114,6 +114,8 @@ class Options
 end
 
 module Homebrew
+  module_function
+
   def dump_options_for_formula(f)
     f.options.sort_by(&:flag).each do |opt|
       puts "#{opt.flag}\n\t#{opt.description}"
diff --git a/Library/Homebrew/test/test_utils.rb b/Library/Homebrew/test/test_utils.rb
index a40a567759..cd5a379ab4 100644
--- a/Library/Homebrew/test/test_utils.rb
+++ b/Library/Homebrew/test/test_utils.rb
@@ -60,7 +60,7 @@ class UtilTests < Homebrew::TestCase
 
   def test_ofail
     shutup { ofail "foo" }
-    assert Homebrew.failed
+    assert Homebrew.failed?
   ensure
     Homebrew.failed = false
   end
diff --git a/Library/Homebrew/utils.rb b/Library/Homebrew/utils.rb
index 8d91c15c0d..04d1572621 100644
--- a/Library/Homebrew/utils.rb
+++ b/Library/Homebrew/utils.rb
@@ -151,7 +151,9 @@ def interactive_shell(f = nil)
 end
 
 module Homebrew
-  def self._system(cmd, *args)
+  module_function
+
+  def _system(cmd, *args)
     pid = fork do
       yield if block_given?
       args.collect!(&:to_s)
@@ -166,12 +168,12 @@ module Homebrew
     $?.success?
   end
 
-  def self.system(cmd, *args)
+  def system(cmd, *args)
     puts "#{cmd} #{args*" "}" if ARGV.verbose?
     _system(cmd, *args)
   end
 
-  def self.core_tap_version_string
+  def core_tap_version_string
     require "tap"
     tap = CoreTap.instance
     return "N/A" unless tap.installed?
@@ -183,7 +185,7 @@ module Homebrew
     end
   end
 
-  def self.install_gem_setup_path!(name, version = nil, executable = name)
+  def install_gem_setup_path!(name, version = nil, executable = name)
     # Respect user's preferences for where gems should be installed.
     ENV["GEM_HOME"] = ENV["GEM_OLD_HOME"].to_s
     ENV["GEM_HOME"] = Gem.user_dir if ENV["GEM_HOME"].empty?
@@ -218,20 +220,19 @@ module Homebrew
       odie "Failed to install/update the '#{name}' gem." if exit_code.nonzero?
     end
 
-    unless which executable
-      odie <<-EOS.undent
-        The '#{name}' gem is installed but couldn't find '#{executable}' in the PATH:
-        #{ENV["PATH"]}
-      EOS
-    end
+    return if which(executable)
+    odie <<-EOS.undent
+      The '#{name}' gem is installed but couldn't find '#{executable}' in the PATH:
+      #{ENV["PATH"]}
+    EOS
   end
 
   # Hash of Module => Set(method_names)
-  @@injected_dump_stat_modules = {}
+  @injected_dump_stat_modules = {}
 
   def inject_dump_stats!(the_module, pattern)
-    @@injected_dump_stat_modules[the_module] ||= []
-    injected_methods = @@injected_dump_stat_modules[the_module]
+    @injected_dump_stat_modules[the_module] ||= []
+    injected_methods = @injected_dump_stat_modules[the_module]
     the_module.module_eval do
       instance_methods.grep(pattern).each do |name|
         next if injected_methods.include? name