favor flat_map over map...flatten

Library/Homebrew/cmd/audit.rb

@@ -242,7 +242,7 @@ class FormulaAuditor
     if @online
       same_name_tap_formulae += @@remote_official_taps.map do |tap|
         Thread.new { Homebrew.search_tap "homebrew", tap, name }
-      end.map(&:value).flatten
+      end.flat_map(&:value)
     end
 
     same_name_tap_formulae.delete(full_name)

Library/Homebrew/cmd/commands.rb

@@ -26,7 +26,7 @@ module Homebrew
   end
 
   def external_commands
-    paths.map { |p| Dir["#{p}/brew-*"] }.flatten.
+    paths.flat_map { |p| Dir["#{p}/brew-*"] }.
       map { |f| File.basename(f, ".rb")[5..-1] }.
       reject { |f| f =~ /\./ }
   end

Library/Homebrew/cmd/doctor.rb

@@ -1220,7 +1220,7 @@ class Checks
   end
 
   def check_for_external_cmd_name_conflict
-    cmds = paths.map { |p| Dir["#{p}/brew-*"] }.flatten.uniq
+    cmds = paths.flat_map { |p| Dir["#{p}/brew-*"] }.uniq
     cmds = cmds.select { |cmd| File.file?(cmd) && File.executable?(cmd) }
     cmd_map = {}
     cmds.each do |cmd|

Library/Homebrew/cmd/list.rb

@@ -68,8 +68,8 @@ module Homebrew
     dirs.delete "var"
 
     args = dirs + %w[-type f (]
-    args.concat UNBREWED_EXCLUDE_FILES.map { |f| %W[! -name #{f}] }.flatten
+    args.concat UNBREWED_EXCLUDE_FILES.flat_map { |f| %W[! -name #{f}] }
-    args.concat UNBREWED_EXCLUDE_PATHS.map { |d| %W[! -path #{d}] }.flatten
+    args.concat UNBREWED_EXCLUDE_PATHS.flat_map { |d| %W[! -path #{d}] }
     args.concat %w[)]
 
     cd HOMEBREW_PREFIX

Library/Homebrew/dependency.rb

@@ -124,7 +124,7 @@ class Dependency
       all.map(&:name).uniq.map do |name|
         deps = grouped.fetch(name)
         dep  = deps.first
-        tags = deps.map(&:tags).flatten.uniq
+        tags = deps.flat_map(&:tags).uniq
         dep.class.new(name, tags, dep.env_proc)
       end
     end

Library/Homebrew/extend/ENV/shared.rb

@@ -29,7 +29,7 @@ module SharedEnvExtension
 
   def remove_cc_etc
     keys = %w[CC CXX OBJC OBJCXX LD CPP CFLAGS CXXFLAGS OBJCFLAGS OBJCXXFLAGS LDFLAGS CPPFLAGS]
-    removed = Hash[*keys.map { |key| [key, self[key]] }.flatten]
+    removed = Hash[*keys.flat_map { |key| [key, self[key]] }]
     keys.each do |key|
       delete(key)
     end

Library/Homebrew/formula.rb

@@ -757,12 +757,12 @@ class Formula
 
   # an array of all tap {Formula} names
   def self.tap_names
-    @tap_names ||= Tap.map(&:formula_names).flatten.sort
+    @tap_names ||= Tap.flat_map(&:formula_names).sort
   end
 
   # an array of all tap {Formula} files
   def self.tap_files
-    @tap_files ||= Tap.map(&:formula_files).flatten
+    @tap_files ||= Tap.flat_map(&:formula_files)
   end
 
   # an array of all {Formula} names