diagnostic: prefer guard clauses for readability

Guard clauses instead of if/unless blocks make the checks easier to
understand and reduce nesting, thus improving overall readability.

This includes the following additional minor changes:

- Make indentation of commands consistent inside diagnostic messages.
- Fix minor typos and inconsistent punctuation in diagnostic messages.
- Fix here documents to always start with `<<-EOS.undent` on a new line,
  followed by the message (indented once), followed by `EOS` (at the
  same level like `<<-EOS.undent`).
- Always separate the check logic (and guard clauses) from the following
  message by a single empty line (for consistency and readability).
- Standardize on `message` as the variable name when diagnostic messages
  need to be constructed from multiple parts.
- Where easily possible, adapt check logic to stay within 80-column
  limit, use more expressive variable names, and break down long
  expressions into multiple statements with intermediate results.

Closes #49.

Signed-off-by: Martin Afanasjew <martin@afanasjew.de>

1 files changed, 502 insertions, 427 deletions

diff --git a/Library/Homebrew/diagnostic.rb b/Library/Homebrew/diagnostic.rb
index 7a133eb24..f42d8b28e 100644
--- a/Library/Homebrew/diagnostic.rb
+++ b/Library/Homebrew/diagnostic.rb
@@ -102,8 +102,10 @@ module Homebrew
 
       # See https://github.com/Homebrew/homebrew/pull/9986
       def check_path_for_trailing_slashes
-        bad_paths = ENV["PATH"].split(File::PATH_SEPARATOR).select { |p| p[-1..-1] == "/" }
+        all_paths = ENV["PATH"].split(File::PATH_SEPARATOR)
+        bad_paths = all_paths.select { |p| p[-1..-1] == "/" }
         return if bad_paths.empty?
+
         inject_file_list bad_paths, <<-EOS.undent
           Some directories in your path end in a slash.
           Directories in your path should not end in a slash. This can break other
@@ -121,13 +123,13 @@ module Homebrew
           /Library/Receipts/libiconv1.pkg
           /usr/local/MacGPG2
         ]
+        return unless suspects.any? { |f| File.exist? f }
 
-        if suspects.any? { |f| File.exist? f } then <<-EOS.undent
+        <<-EOS.undent
           You may have installed MacGPG2 via the package installer.
           Several other checks in this script will turn up problems, such as stray
           dylibs in /usr/local and permissions issues with share and man in /usr/local/.
         EOS
-        end
       end
 
       # Anaconda installs multiple system & brew dupes, including OpenSSL, Python,
@@ -138,12 +140,14 @@ module Homebrew
         return unless which("anaconda")
         return unless which("python")
 
-        anaconda = which("anaconda").realpath.dirname
+        anaconda_directory = which("anaconda").realpath.dirname
         python_binary = Utils.popen_read which("python"), "-c", "import sys; sys.stdout.write(sys.executable)"
-        python = Pathname.new(python_binary).realpath.dirname
+        python_directory = Pathname.new(python_binary).realpath.dirname
 
         # Only warn if Python lives with Anaconda, since is most problematic case.
-        if python == anaconda then <<-EOS.undent
+        return unless python_directory == anaconda_directory
+
+        <<-EOS.undent
           Anaconda is known to frequently break Homebrew builds, including Vim and
           MacVim, due to bundling many duplicates of system and Homebrew-available
           tools.
@@ -152,7 +156,6 @@ module Homebrew
           from your $PATH and attempt the build again prior to reporting the
           failure to us. Thanks!
         EOS
-        end
       end
 
       def __check_stray_files(dir, pattern, white_list, message)
@@ -161,8 +164,9 @@ module Homebrew
         files = Dir.chdir(dir) do
           Dir[pattern].select { |f| File.file?(f) && !File.symlink?(f) } - Dir.glob(white_list)
         end.map { |file| File.join(dir, file) }
+        return if files.empty?
 
-        inject_file_list(files, message) unless files.empty?
+        inject_file_list(files, message)
       end
 
       def check_for_stray_dylibs
@@ -185,12 +189,12 @@ module Homebrew
         ]
 
         __check_stray_files "/usr/local/lib", "*.dylib", white_list, <<-EOS.undent
-        Unbrewed dylibs were found in /usr/local/lib.
-        If you didn't put them there on purpose they could cause problems when
-        building Homebrew formulae, and may need to be deleted.
+          Unbrewed dylibs were found in /usr/local/lib.
+          If you didn't put them there on purpose they could cause problems when
+          building Homebrew formulae, and may need to be deleted.
 
-        Unexpected dylibs:
-      EOS
+          Unexpected dylibs:
+        EOS
       end
 
       def check_for_stray_static_libs
@@ -205,12 +209,12 @@ module Homebrew
         ]
 
         __check_stray_files "/usr/local/lib", "*.a", white_list, <<-EOS.undent
-        Unbrewed static libraries were found in /usr/local/lib.
-        If you didn't put them there on purpose they could cause problems when
-        building Homebrew formulae, and may need to be deleted.
+          Unbrewed static libraries were found in /usr/local/lib.
+          If you didn't put them there on purpose they could cause problems when
+          building Homebrew formulae, and may need to be deleted.
 
-        Unexpected static libraries:
-      EOS
+          Unexpected static libraries:
+        EOS
       end
 
       def check_for_stray_pcs
@@ -225,12 +229,12 @@ module Homebrew
         ]
 
         __check_stray_files "/usr/local/lib/pkgconfig", "*.pc", white_list, <<-EOS.undent
-        Unbrewed .pc files were found in /usr/local/lib/pkgconfig.
-        If you didn't put them there on purpose they could cause problems when
-        building Homebrew formulae, and may need to be deleted.
+          Unbrewed .pc files were found in /usr/local/lib/pkgconfig.
+          If you didn't put them there on purpose they could cause problems when
+          building Homebrew formulae, and may need to be deleted.
 
-        Unexpected .pc files:
-      EOS
+          Unexpected .pc files:
+        EOS
       end
 
       def check_for_stray_las
@@ -246,12 +250,12 @@ module Homebrew
         ]
 
         __check_stray_files "/usr/local/lib", "*.la", white_list, <<-EOS.undent
-        Unbrewed .la files were found in /usr/local/lib.
-        If you didn't put them there on purpose they could cause problems when
-        building Homebrew formulae, and may need to be deleted.
+          Unbrewed .la files were found in /usr/local/lib.
+          If you didn't put them there on purpose they could cause problems when
+          building Homebrew formulae, and may need to be deleted.
 
-        Unexpected .la files:
-      EOS
+          Unexpected .la files:
+        EOS
       end
 
       def check_for_stray_headers
@@ -265,18 +269,19 @@ module Homebrew
         ]
 
         __check_stray_files "/usr/local/include", "**/*.h", white_list, <<-EOS.undent
-        Unbrewed header files were found in /usr/local/include.
-        If you didn't put them there on purpose they could cause problems when
-        building Homebrew formulae, and may need to be deleted.
+          Unbrewed header files were found in /usr/local/include.
+          If you didn't put them there on purpose they could cause problems when
+          building Homebrew formulae, and may need to be deleted.
 
-        Unexpected header files:
-      EOS
+          Unexpected header files:
+        EOS
       end
 
       def check_for_other_package_managers
         ponk = MacOS.macports_or_fink
-        unless ponk.empty?
-          <<-EOS.undent
+        return if ponk.empty?
+
+        <<-EOS.undent
           You have MacPorts or Fink installed:
             #{ponk.join(", ")}
 
@@ -285,7 +290,6 @@ module Homebrew
 
             sudo mv /opt/local ~/macports
         EOS
-        end
       end
 
       def check_for_broken_symlinks
@@ -300,155 +304,163 @@ module Homebrew
           end
         end
         return if broken_symlinks.empty?
+
         inject_file_list broken_symlinks, <<-EOS.undent
-        Broken symlinks were found. Remove them with `brew prune`:
+          Broken symlinks were found. Remove them with `brew prune`:
         EOS
       end
 
       def check_for_unsupported_osx
         return if ARGV.homebrew_developer?
+
+        who = "We"
         if OS::Mac.prerelease?
-          <<-EOS.undent
-            You are using OS X #{MacOS.version}.
-            We do not provide support for this pre-release version.
-            You may encounter build failures or other breakages.
-          EOS
+          what = "pre-release version"
         elsif OS::Mac.outdated_release?
-          <<-EOS.undent
-            You are using OS X #{MacOS.version}.
-            We (and Apple) do not provide support for this old version.
-            You may encounter build failures or other breakages.
-          EOS
+          who << " (and Apple)"
+          what = "old version"
+        else
+          return
         end
+
+        <<-EOS.undent
+          You are using OS X #{MacOS.version}.
+          #{who} do not provide support for this #{what}.
+          You may encounter build failures or other breakages.
+        EOS
       end
 
       # TODO: distill down into single method definition a la BuildToolsError
       if MacOS.version >= "10.9"
         def check_for_installed_developer_tools
-          unless MacOS::Xcode.installed? || MacOS::CLT.installed? then <<-EOS.undent
-          No developer tools installed.
-          Install the Command Line Tools:
-            xcode-select --install
+          return if MacOS::Xcode.installed? || MacOS::CLT.installed?
+
+          <<-EOS.undent
+            No developer tools installed.
+            Install the Command Line Tools:
+              xcode-select --install
           EOS
-          end
         end
 
         if OS::Mac.prerelease?
           def check_xcode_up_to_date
-            if MacOS::Xcode.installed? && MacOS::Xcode.outdated?
-              <<-EOS.undent
-            Your Xcode (#{MacOS::Xcode.version}) is outdated
-            Please update to Xcode #{MacOS::Xcode.latest_version}.
-            Xcode can be updated from
-              https://developer.apple.com/xcode/downloads/
+            return unless MacOS::Xcode.installed? && MacOS::Xcode.outdated?
+
+            <<-EOS.undent
+              Your Xcode (#{MacOS::Xcode.version}) is outdated
+              Please update to Xcode #{MacOS::Xcode.latest_version}.
+              Xcode can be updated from
+                https://developer.apple.com/xcode/downloads/
             EOS
-            end
           end
         else
           def check_xcode_up_to_date
-            if MacOS::Xcode.installed? && MacOS::Xcode.outdated?
-              <<-EOS.undent
-            Your Xcode (#{MacOS::Xcode.version}) is outdated
-            Please update to Xcode #{MacOS::Xcode.latest_version}.
-            Xcode can be updated from the App Store.
+            return unless MacOS::Xcode.installed? && MacOS::Xcode.outdated?
+
+            <<-EOS.undent
+              Your Xcode (#{MacOS::Xcode.version}) is outdated
+              Please update to Xcode #{MacOS::Xcode.latest_version}.
+              Xcode can be updated from the App Store.
             EOS
-            end
           end
         end
 
         def check_clt_up_to_date
-          if MacOS::CLT.installed? && MacOS::CLT.outdated? then <<-EOS.undent
-          A newer Command Line Tools release is available.
-          Update them from Software Update in the App Store.
+          return unless MacOS::CLT.installed? && MacOS::CLT.outdated?
+
+          <<-EOS.undent
+            A newer Command Line Tools release is available.
+            Update them from Software Update in the App Store.
           EOS
-          end
         end
       elsif MacOS.version == "10.8" || MacOS.version == "10.7"
         def check_for_installed_developer_tools
-          unless MacOS::Xcode.installed? || MacOS::CLT.installed? then <<-EOS.undent
-          No developer tools installed.
-          You should install the Command Line Tools.
-          The standalone package can be obtained from
-            https://developer.apple.com/downloads
-          or it can be installed via Xcode's preferences.
+          return if MacOS::Xcode.installed? || MacOS::CLT.installed?
+
+          <<-EOS.undent
+            No developer tools installed.
+            You should install the Command Line Tools.
+            The standalone package can be obtained from
+              https://developer.apple.com/downloads
+            or it can be installed via Xcode's preferences.
           EOS
-          end
         end
 
         def check_xcode_up_to_date
-          if MacOS::Xcode.installed? && MacOS::Xcode.outdated? then <<-EOS.undent
-          Your Xcode (#{MacOS::Xcode.version}) is outdated
-          Please update to Xcode #{MacOS::Xcode.latest_version}.
-          Xcode can be updated from
-            https://developer.apple.com/xcode/downloads/
+          return unless MacOS::Xcode.installed? && MacOS::Xcode.outdated?
+
+          <<-EOS.undent
+            Your Xcode (#{MacOS::Xcode.version}) is outdated
+            Please update to Xcode #{MacOS::Xcode.latest_version}.
+            Xcode can be updated from
+              https://developer.apple.com/xcode/downloads/
           EOS
-          end
         end
 
         def check_clt_up_to_date
-          if MacOS::CLT.installed? && MacOS::CLT.outdated? then <<-EOS.undent
-          A newer Command Line Tools release is available.
-          The standalone package can be obtained from
-            https://developer.apple.com/downloads
-          or it can be installed via Xcode's preferences.
+          return unless MacOS::CLT.installed? && MacOS::CLT.outdated?
+
+          <<-EOS.undent
+            A newer Command Line Tools release is available.
+            The standalone package can be obtained from
+              https://developer.apple.com/downloads
+            or it can be installed via Xcode's preferences.
           EOS
-          end
         end
       else
         def check_for_installed_developer_tools
-          unless MacOS::Xcode.installed? then <<-EOS.undent
-          Xcode is not installed. Most formulae need Xcode to build.
-          It can be installed from
-            https://developer.apple.com/xcode/downloads/
+          return if MacOS::Xcode.installed?
+
+          <<-EOS.undent
+            Xcode is not installed. Most formulae need Xcode to build.
+            It can be installed from
+              https://developer.apple.com/xcode/downloads/
           EOS
-          end
         end
 
         def check_xcode_up_to_date
-          if MacOS::Xcode.installed? && MacOS::Xcode.outdated? then <<-EOS.undent
-          Your Xcode (#{MacOS::Xcode.version}) is outdated
-          Please update to Xcode #{MacOS::Xcode.latest_version}.
-          Xcode can be updated from
-            https://developer.apple.com/xcode/downloads/
+          return unless MacOS::Xcode.installed? && MacOS::Xcode.outdated?
+
+          <<-EOS.undent
+            Your Xcode (#{MacOS::Xcode.version}) is outdated
+            Please update to Xcode #{MacOS::Xcode.latest_version}.
+            Xcode can be updated from
+              https://developer.apple.com/xcode/downloads/
           EOS
-          end
         end
       end
 
       def check_for_osx_gcc_installer
-        if (MacOS.version < "10.7" || MacOS::Xcode.version > "4.1") && \
-          MacOS.clang_version == "2.1"
-          message = <<-EOS.undent
-        You seem to have osx-gcc-installer installed.
-        Homebrew doesn't support osx-gcc-installer. It causes many builds to fail and
-        is an unlicensed distribution of really old Xcode files.
-        EOS
-          if MacOS.version >= :mavericks
-            message += <<-EOS.undent
-              Please run `xcode-select --install` to install the CLT.
-            EOS
-          elsif MacOS.version >= :lion
-            message += <<-EOS.undent
-            Please install the CLT or Xcode #{MacOS::Xcode.latest_version}.
-          EOS
-          else
-            message += <<-EOS.undent
-            Please install Xcode #{MacOS::Xcode.latest_version}.
-          EOS
-          end
+        return unless MacOS.version < "10.7" || MacOS::Xcode.version > "4.1"
+        return unless MacOS.clang_version == "2.1"
+
+        fix_advice = if MacOS.version >= :mavericks
+          "Please run `xcode-select --install` to install the CLT."
+        elsif MacOS.version >= :lion
+          "Please install the CLT or Xcode #{MacOS::Xcode.latest_version}."
+        else
+          "Please install Xcode #{MacOS::Xcode.latest_version}."
         end
+
+        <<-EOS.undent
+          You seem to have osx-gcc-installer installed.
+          Homebrew doesn't support osx-gcc-installer. It causes many builds to fail and
+          is an unlicensed distribution of really old Xcode files.
+          #{fix_advice}
+        EOS
       end
 
       def check_for_stray_developer_directory
         # if the uninstaller script isn't there, it's a good guess neither are
         # any troublesome leftover Xcode files
         uninstaller = Pathname.new("/Developer/Library/uninstall-developer-folder")
-        if MacOS::Xcode.version >= "4.3" && uninstaller.exist? then <<-EOS.undent
-        You have leftover files from an older version of Xcode.
-        You should delete them using:
-          #{uninstaller}
+        return unless MacOS::Xcode.version >= "4.3" && uninstaller.exist?
+
+        <<-EOS.undent
+          You have leftover files from an older version of Xcode.
+          You should delete them using:
+            #{uninstaller}
         EOS
-        end
       end
 
       def check_for_bad_install_name_tool
@@ -476,13 +488,12 @@ module Homebrew
         return unless target.exist?
 
         cant_read = []
-
         target.find do |d|
           next unless d.directory?
           cant_read << d unless d.writable_real?
         end
-
         return if cant_read.empty?
+
         inject_file_list cant_read.sort, <<-EOS.undent
           Some directories in #{target} aren't writable.
           This can happen if you "sudo make install" software that isn't managed
@@ -502,72 +513,78 @@ module Homebrew
       end
 
       def check_access_homebrew_repository
-        unless HOMEBREW_REPOSITORY.writable_real? then <<-EOS.undent
+        return if HOMEBREW_REPOSITORY.writable_real?
+
+        <<-EOS.undent
           #{HOMEBREW_REPOSITORY} is not writable.
 
           You should probably change the ownership and permissions of #{HOMEBREW_REPOSITORY}
           back to your user account.
             sudo chown -R $(whoami) #{HOMEBREW_REPOSITORY}
         EOS
-        end
       end
 
       def check_access_usr_local
         return unless HOMEBREW_PREFIX.to_s == "/usr/local"
+        return if HOMEBREW_PREFIX.writable_real?
 
-        unless HOMEBREW_PREFIX.writable_real? then <<-EOS.undent
-        /usr/local is not writable.
-        Even if this directory was writable when you installed Homebrew, other
-        software may change permissions on this directory. For example, upgrading
-        to OS X El Capitan has been known to do this. Some versions of the
-        "InstantOn" component of Airfoil or running Cocktail cleanup/optimizations
-        are known to do this as well.
-
-        You should probably change the ownership and permissions of /usr/local
-        back to your user account.
-          sudo chown -R $(whoami) /usr/local
+        <<-EOS.undent
+          /usr/local is not writable.
+          Even if this directory was writable when you installed Homebrew, other
+          software may change permissions on this directory. For example, upgrading
+          to OS X El Capitan has been known to do this. Some versions of the
+          "InstantOn" component of Airfoil or running Cocktail cleanup/optimizations
+          are known to do this as well.
+
+          You should probably change the ownership and permissions of /usr/local
+          back to your user account.
+            sudo chown -R $(whoami) /usr/local
         EOS
-        end
       end
 
       def check_tmpdir_sticky_bit
-        # Repair Disk Permissions was removed(?) in El Capitan.
+        world_writable = HOMEBREW_TEMP.stat.mode & 0777 == 0777
+        return if !world_writable || HOMEBREW_TEMP.sticky?
+
+        # Repair Disk Permissions was removed in El Capitan.
         # https://support.apple.com/en-us/HT201560
-        if MacOS.version < "10.11"
-          fix_message = "Please run \"Repair Disk Permissions\" in Disk Utility."
+        fix_advice = if MacOS.version < "10.11"
+          "Please run \"Repair Disk Permissions\" in Disk Utility."
         else
-          fix_message = "Please execute `sudo chmod +t #{HOMEBREW_TEMP}` in your Terminal"
+          "Please execute `sudo chmod +t #{HOMEBREW_TEMP}` in your Terminal."
         end
 
-        world_writable = HOMEBREW_TEMP.stat.mode & 0777 == 0777
-        if world_writable && !HOMEBREW_TEMP.sticky? then <<-EOS.undent
-        #{HOMEBREW_TEMP} is world-writable but does not have the sticky bit set.
-        #{fix_message}
+        <<-EOS.undent
+          #{HOMEBREW_TEMP} is world-writable but does not have the sticky bit set.
+          #{fix_advice}
         EOS
-        end
       end
 
       (Keg::TOP_LEVEL_DIRECTORIES + ["lib/pkgconfig"]).each do |d|
         define_method("check_access_#{d.sub("/", "_")}") do
           dir = HOMEBREW_PREFIX.join(d)
-          if dir.exist? && !dir.writable_real? then <<-EOS.undent
-          #{dir} isn't writable.
+          return unless dir.exist?
+          return if dir.writable_real?
 
-          This can happen if you "sudo make install" software that isn't managed
-          by Homebrew. If a formula tries to write a file to this directory, the
-          install will fail during the link step.
+          <<-EOS.undent
+            #{dir} isn't writable.
 
-          You should probably change the ownership and permissions of #{dir}
-          back to your user account.
-            sudo chown -R $(whoami) #{dir}
+            This can happen if you "sudo make install" software that isn't managed
+            by Homebrew. If a formula tries to write a file to this directory, the
+            install will fail during the link step.
+
+            You should probably change the ownership and permissions of #{dir}
+            back to your user account.
+              sudo chown -R $(whoami) #{dir}
           EOS
-          end
         end
       end
 
       def check_access_site_packages
-        if Language::Python.homebrew_site_packages.exist? && !Language::Python.homebrew_site_packages.writable_real?
-          <<-EOS.undent
+        return unless Language::Python.homebrew_site_packages.exist?
+        return if Language::Python.homebrew_site_packages.writable_real?
+
+        <<-EOS.undent
           #{Language::Python.homebrew_site_packages} isn't writable.
           This can happen if you "sudo pip install" software that isn't managed
           by Homebrew. If you install a formula with Python modules, the install
@@ -577,12 +594,13 @@ module Homebrew
           back to your user account.
             sudo chown -R $(whoami) #{Language::Python.homebrew_site_packages}
         EOS
-        end
       end
 
       def check_access_logs
-        if HOMEBREW_LOGS.exist? && !HOMEBREW_LOGS.writable_real?
-          <<-EOS.undent
+        return unless HOMEBREW_LOGS.exist?
+        return if HOMEBREW_LOGS.writable_real?
+
+        <<-EOS.undent
           #{HOMEBREW_LOGS} isn't writable.
           Homebrew writes debugging logs to this location.
 
@@ -590,12 +608,13 @@ module Homebrew
           back to your user account.
             sudo chown -R $(whoami) #{HOMEBREW_LOGS}
         EOS
-        end
       end
 
       def check_access_cache
-        if HOMEBREW_CACHE.exist? && !HOMEBREW_CACHE.writable_real?
-          <<-EOS.undent
+        return unless HOMEBREW_CACHE.exist?
+        return if HOMEBREW_CACHE.writable_real?
+
+        <<-EOS.undent
           #{HOMEBREW_CACHE} isn't writable.
           This can happen if you run `brew install` or `brew fetch` as another user.
           Homebrew caches downloaded files to this location.
@@ -604,94 +623,97 @@ module Homebrew
           back to your user account.
             sudo chown -R $(whoami) #{HOMEBREW_CACHE}
         EOS
-        end
       end
 
       def check_access_cellar
-        if HOMEBREW_CELLAR.exist? && !HOMEBREW_CELLAR.writable_real?
-          <<-EOS.undent
+        return unless HOMEBREW_CELLAR.exist?
+        return if HOMEBREW_CELLAR.writable_real?
+
+        <<-EOS.undent
           #{HOMEBREW_CELLAR} isn't writable.
 
           You should probably change the ownership and permissions of #{HOMEBREW_CELLAR}
           back to your user account.
             sudo chown -R $(whoami) #{HOMEBREW_CELLAR}
         EOS
-        end
       end
 
       def check_access_prefix_opt
         opt = HOMEBREW_PREFIX.join("opt")
-        if opt.exist? && !opt.writable_real?
-          <<-EOS.undent
+        return unless opt.exist?
+        return if opt.writable_real?
+
+        <<-EOS.undent
           #{opt} isn't writable.
+
           You should probably change the ownership and permissions of #{opt}
           back to your user account.
             sudo chown -R $(whoami) #{opt}
         EOS
-        end
       end
 
       def check_ruby_version
         ruby_version = MacOS.version >= "10.9" ? "2.0" : "1.8"
-        if RUBY_VERSION[/\d\.\d/] != ruby_version then <<-EOS.undent
-        Ruby version #{RUBY_VERSION} is unsupported on #{MacOS.version}. Homebrew
-        is developed and tested on Ruby #{ruby_version}, and may not work correctly
-        on other Rubies. Patches are accepted as long as they don't cause breakage
-        on supported Rubies.
+        return if RUBY_VERSION[/\d\.\d/] == ruby_version
+
+        <<-EOS.undent
+          Ruby version #{RUBY_VERSION} is unsupported on #{MacOS.version}. Homebrew
+          is developed and tested on Ruby #{ruby_version}, and may not work correctly
+          on other Rubies. Patches are accepted as long as they don't cause breakage
+          on supported Rubies.
         EOS
-        end
       end
 
       def check_homebrew_prefix
-        unless HOMEBREW_PREFIX.to_s == "/usr/local"
-          <<-EOS.undent
+        return if HOMEBREW_PREFIX.to_s == "/usr/local"
+
+        <<-EOS.undent
           Your Homebrew is not installed to /usr/local
           You can install Homebrew anywhere you want, but some brews may only build
           correctly if you install in /usr/local. Sorry!
         EOS
-        end
       end
 
       def check_xcode_prefix
         prefix = MacOS::Xcode.prefix
         return if prefix.nil?
-        if prefix.to_s.match(" ")
-          <<-EOS.undent
+        return unless prefix.to_s.include?(" ")
+
+        <<-EOS.undent
           Xcode is installed to a directory with a space in the name.
           This will cause some formulae to fail to build.
         EOS
-        end
       end
 
       def check_xcode_prefix_exists
         prefix = MacOS::Xcode.prefix
-        return if prefix.nil?
-        unless prefix.exist?
-          <<-EOS.undent
+        return if prefix.nil? || prefix.exist?
+
+        <<-EOS.undent
           The directory Xcode is reportedly installed to doesn't exist:
             #{prefix}
           You may need to `xcode-select` the proper path if you have moved Xcode.
         EOS
-        end
       end
 
       def check_xcode_select_path
-        if !MacOS::CLT.installed? && !File.file?("#{MacOS.active_developer_dir}/usr/bin/xcodebuild")
-          path = MacOS::Xcode.bundle_path
-          path = "/Developer" if path.nil? || !path.directory?
-          <<-EOS.undent
+        return if MacOS::CLT.installed?
+        return if File.file?("#{MacOS.active_developer_dir}/usr/bin/xcodebuild")
+
+        path = MacOS::Xcode.bundle_path
+        path = "/Developer" if path.nil? || !path.directory?
+        <<-EOS.undent
           Your Xcode is configured with an invalid path.
           You should change it to the correct path:
             sudo xcode-select -switch #{path}
         EOS
-        end
       end
 
       def check_user_path_1
         $seen_prefix_bin = false
         $seen_prefix_sbin = false
 
-        out = nil
+        message = ""
 
         paths.each do |p|
           case p
@@ -704,18 +726,18 @@ module Homebrew
                           select { |bn| File.exist? "/usr/bin/#{bn}" }
 
               if conflicts.size > 0
-                out = inject_file_list conflicts, <<-EOS.undent
-                /usr/bin occurs before #{HOMEBREW_PREFIX}/bin
-                This means that system-provided programs will be used instead of those
-                provided by Homebrew. The following tools exist at both paths:
+                message = inject_file_list conflicts, <<-EOS.undent
+                  /usr/bin occurs before #{HOMEBREW_PREFIX}/bin
+                  This means that system-provided programs will be used instead of those
+                  provided by Homebrew. The following tools exist at both paths:
                 EOS
 
-                out += <<-EOS.undent
+                message += <<-EOS.undent
 
-                Consider setting your PATH so that #{HOMEBREW_PREFIX}/bin
-                occurs before /usr/bin. Here is a one-liner:
+                  Consider setting your PATH so that #{HOMEBREW_PREFIX}/bin
+                  occurs before /usr/bin. Here is a one-liner:
                     echo 'export PATH="#{HOMEBREW_PREFIX}/bin:$PATH"' >> #{shell_profile}
-              EOS
+                EOS
               end
             end
           when "#{HOMEBREW_PREFIX}/bin"
@@ -724,65 +746,74 @@ module Homebrew
             $seen_prefix_sbin = true
           end
         end
-        out
+
+        message unless message.empty?
       end
 
       def check_user_path_2
-        unless $seen_prefix_bin
-          <<-EOS.undent
+        return if $seen_prefix_bin
+
+        <<-EOS.undent
           Homebrew's bin was not found in your PATH.
           Consider setting the PATH for example like so
-              echo 'export PATH="#{HOMEBREW_PREFIX}/bin:$PATH"' >> #{shell_profile}
+            echo 'export PATH="#{HOMEBREW_PREFIX}/bin:$PATH"' >> #{shell_profile}
         EOS
-        end
       end
 
       def check_user_path_3
+        return if $seen_prefix_sbin
+
         # Don't complain about sbin not being in the path if it doesn't exist
         sbin = (HOMEBREW_PREFIX+"sbin")
-        if sbin.directory? && sbin.children.length > 0
-          unless $seen_prefix_sbin
-            <<-EOS.undent
-            Homebrew's sbin was not found in your PATH but you have installed
-            formulae that put executables in #{HOMEBREW_PREFIX}/sbin.
-            Consider setting the PATH for example like so
-                echo 'export PATH="#{HOMEBREW_PREFIX}/sbin:$PATH"' >> #{shell_profile}
-          EOS
-          end
-        end
+        return unless sbin.directory? && sbin.children.length > 0
+
+        <<-EOS.undent
+          Homebrew's sbin was not found in your PATH but you have installed
+          formulae that put executables in #{HOMEBREW_PREFIX}/sbin.
+          Consider setting the PATH for example like so
+            echo 'export PATH="#{HOMEBREW_PREFIX}/sbin:$PATH"' >> #{shell_profile}
+        EOS
       end
 
       def check_for_bad_curl
-        if MacOS.version <= "10.8" && !Formula["curl"].installed? then <<-EOS.undent
+        return unless MacOS.version <= "10.8"
+        return if Formula["curl"].installed?
+
+        <<-EOS.undent
           The system curl on 10.8 and below is often incapable of supporting
           modern secure connections & will fail on fetching formulae.
 
           We recommend you:
             brew install curl
-          EOS
-        end
+        EOS
       end
 
       def check_user_curlrc
-        if %w[CURL_HOME HOME].any? { |key| ENV[key] && File.exist?("#{ENV[key]}/.curlrc") } then <<-EOS.undent
-        You have a curlrc file
-        If you have trouble downloading packages with Homebrew, then maybe this
-        is the problem? If the following command doesn't work, then try removing
-        your curlrc:
-          curl https://github.com
-        EOS
+        curlrc_found = %w[CURL_HOME HOME].any? do |var|
+          ENV[var] && File.exist?("#{ENV[var]}/.curlrc")
         end
+        return unless curlrc_found
+
+        <<-EOS.undent
+          You have a curlrc file
+          If you have trouble downloading packages with Homebrew, then maybe this
+          is the problem? If the following command doesn't work, then try removing
+          your curlrc:
+            curl https://github.com
+        EOS
       end
 
       def check_for_unsupported_curl_vars
         # Support for SSL_CERT_DIR seemed to be removed in the 10.10.5 update.
-        if MacOS.version >= :yosemite && !ENV["SSL_CERT_DIR"].nil? then <<-EOS.undent
+        return unless MacOS.version >= :yosemite
+        return if ENV["SSL_CERT_DIR"].nil?
+
+        <<-EOS.undent
           SSL_CERT_DIR support was removed from Apple's curl.
           If fetching formulae fails you should:
             unset SSL_CERT_DIR
           and remove it from #{shell_profile} if present.
-          EOS
-        end
+        EOS
       end
 
       def check_which_pkg_config
@@ -790,23 +821,25 @@ module Homebrew
         return if binary.nil?
 
         mono_config = Pathname.new("/usr/bin/pkg-config")
-        if mono_config.exist? && mono_config.realpath.to_s.include?("Mono.framework") then <<-EOS.undent
-        You have a non-Homebrew 'pkg-config' in your PATH:
-          /usr/bin/pkg-config => #{mono_config.realpath}
+        if mono_config.exist? && mono_config.realpath.to_s.include?("Mono.framework")
+          <<-EOS.undent
+            You have a non-Homebrew 'pkg-config' in your PATH:
+              /usr/bin/pkg-config => #{mono_config.realpath}
 
-        This was most likely created by the Mono installer. `./configure` may
-        have problems finding brew-installed packages using this other pkg-config.
+            This was most likely created by the Mono installer. `./configure` may
+            have problems finding brew-installed packages using this other pkg-config.
 
-        Mono no longer installs this file as of 3.0.4. You should
-        `sudo rm /usr/bin/pkg-config` and upgrade to the latest version of Mono.
-        EOS
-        elsif binary.to_s != "#{HOMEBREW_PREFIX}/bin/pkg-config" then <<-EOS.undent
-        You have a non-Homebrew 'pkg-config' in your PATH:
-          #{binary}
+            Mono no longer installs this file as of 3.0.4. You should
+            `sudo rm /usr/bin/pkg-config` and upgrade to the latest version of Mono.
+          EOS
+        elsif binary.to_s != "#{HOMEBREW_PREFIX}/bin/pkg-config"
+          <<-EOS.undent
+            You have a non-Homebrew 'pkg-config' in your PATH:
+              #{binary}
 
-        `./configure` may have problems finding brew-installed packages using
-        this other pkg-config.
-        EOS
+            `./configure` may have problems finding brew-installed packages using
+            this other pkg-config.
+          EOS
         end
       end
 
@@ -814,44 +847,45 @@ module Homebrew
         find_relative_paths("lib/libgettextlib.dylib",
                             "lib/libintl.dylib",
                             "include/libintl.h")
-
         return if @found.empty?
 
         # Our gettext formula will be caught by check_linked_keg_only_brews
-        f = Formulary.factory("gettext") rescue nil
-        return if f && f.linked_keg.directory? && @found.all? do |path|
+        gettext = Formulary.factory("gettext") rescue nil
+        homebrew_owned = @found.all? do |path|
           Pathname.new(path).realpath.to_s.start_with? "#{HOMEBREW_CELLAR}/gettext"
         end
+        return if gettext && gettext.linked_keg.directory? && homebrew_owned
 
-        s = <<-EOS.undent_________________________________________________________72
-          gettext files detected at a system prefix
+        inject_file_list @found, <<-EOS.undent
+          gettext files detected at a system prefix.
           These files can cause compilation and link failures, especially if they
           are compiled with improper architectures. Consider removing these files:
-          EOS
-        inject_file_list(@found, s)
+        EOS
       end
 
       def check_for_iconv
-        unless find_relative_paths("lib/libiconv.dylib", "include/iconv.h").empty?
-          if (f = Formulary.factory("libiconv") rescue nil) && f.linked_keg.directory?
-            unless f.keg_only? then <<-EOS.undent
-            A libiconv formula is installed and linked
-            This will break stuff. For serious. Unlink it.
+        find_relative_paths("lib/libiconv.dylib", "include/iconv.h")
+        return if @found.empty?
+
+        libiconv = Formulary.factory("libiconv") rescue nil
+        if libiconv && libiconv.linked_keg.directory?
+          unless libiconv.keg_only?
+            <<-EOS.undent
+              A libiconv formula is installed and linked.
+              This will break stuff. For serious. Unlink it.
             EOS
-            end
-          else
-            s = <<-EOS.undent_________________________________________________________72
-              libiconv files detected at a system prefix other than /usr
-              Homebrew doesn't provide a libiconv formula, and expects to link against
-              the system version in /usr. libiconv in other prefixes can cause
-              compile or link failure, especially if compiled with improper
-              architectures. OS X itself never installs anything to /usr/local so
-              it was either installed by a user or some other third party software.
-
-              tl;dr: delete these files:
-              EOS
-            inject_file_list(@found, s)
           end
+        else
+          inject_file_list @found, <<-EOS.undent
+            libiconv files detected at a system prefix other than /usr.
+            Homebrew doesn't provide a libiconv formula, and expects to link against
+            the system version in /usr. libiconv in other prefixes can cause
+            compile or link failure, especially if compiled with improper
+            architectures. OS X itself never installs anything to /usr/local so
+            it was either installed by a user or some other third party software.
+
+            tl;dr: delete these files:
+          EOS
         end
       end
 
@@ -879,6 +913,7 @@ module Homebrew
         end
 
         return if scripts.empty?
+
         inject_file_list scripts, <<-EOS.undent
           "config" scripts exist outside your system or Homebrew directories.
           `./configure` scripts often look for *-config scripts to determine if
@@ -892,27 +927,32 @@ module Homebrew
       end
 
       def check_DYLD_vars
-        found = ENV.keys.grep(/^DYLD_/)
-        return if found.empty?
-        s = inject_file_list found.map { |e| "#{e}: #{ENV.fetch(e)}" }, <<-EOS.undent
+        dyld_vars = ENV.keys.grep(/^DYLD_/)
+        return if dyld_vars.empty?
+
+        values = dyld_vars.map { |var| "#{var}: #{ENV.fetch(var)}" }
+        message = inject_file_list values, <<-EOS.undent
           Setting DYLD_* vars can break dynamic linking.
           Set variables:
         EOS
-        if found.include? "DYLD_INSERT_LIBRARIES"
-          s += <<-EOS.undent
 
-          Setting DYLD_INSERT_LIBRARIES can cause Go builds to fail.
-          Having this set is common if you use this software:
-            http://asepsis.binaryage.com/
+        if dyld_vars.include? "DYLD_INSERT_LIBRARIES"
+          message += <<-EOS.undent
+
+            Setting DYLD_INSERT_LIBRARIES can cause Go builds to fail.
+            Having this set is common if you use this software:
+              http://asepsis.binaryage.com/
           EOS
         end
-        s
+
+        message
       end
 
       def check_for_symlinked_cellar
         return unless HOMEBREW_CELLAR.exist?
-        if HOMEBREW_CELLAR.symlink?
-          <<-EOS.undent
+        return unless HOMEBREW_CELLAR.symlink?
+
+        <<-EOS.undent
           Symlinked Cellars can cause problems.
           Your Homebrew Cellar is a symlink: #{HOMEBREW_CELLAR}
                           which resolves to: #{HOMEBREW_CELLAR.realpath}
@@ -925,7 +965,6 @@ module Homebrew
           cause problems when two formula install to locations that are mapped on top of each
           other during the linking step.
         EOS
-        end
       end
 
       def check_for_multiple_volumes
@@ -934,71 +973,85 @@ module Homebrew
 
         # Find the volumes for the TMP folder & HOMEBREW_CELLAR
         real_cellar = HOMEBREW_CELLAR.realpath
-
-        tmp = Pathname.new(Dir.mktmpdir("doctor", HOMEBREW_TEMP))
-        real_temp = tmp.realpath.parent
-
         where_cellar = volumes.which real_cellar
-        where_temp = volumes.which real_temp
 
-        Dir.delete tmp
+        tmp = Pathname.new(Dir.mktmpdir("doctor", HOMEBREW_TEMP))
+        begin
+          real_tmp = tmp.realpath.parent
+          where_tmp = volumes.which real_tmp
+        ensure
+          Dir.delete tmp
+        end
+        return if where_cellar == where_tmp
 
-        unless where_cellar == where_temp then <<-EOS.undent
-        Your Cellar and TEMP directories are on different volumes.
-        OS X won't move relative symlinks across volumes unless the target file already
-        exists. Brews known to be affected by this are Git and Narwhal.
+        <<-EOS.undent
+          Your Cellar and TEMP directories are on different volumes.
+          OS X won't move relative symlinks across volumes unless the target file already
+          exists. Brews known to be affected by this are Git and Narwhal.
 
-        You should set the "HOMEBREW_TEMP" environmental variable to a suitable
-        directory on the same volume as your Cellar.
+          You should set the "HOMEBREW_TEMP" environmental variable to a suitable
+          directory on the same volume as your Cellar.
         EOS
-        end
       end
 
       def check_filesystem_case_sensitive
-        volumes = Volumes.new
-        case_sensitive_vols = [HOMEBREW_PREFIX, HOMEBREW_REPOSITORY, HOMEBREW_CELLAR, HOMEBREW_TEMP].select do |dir|
+        dirs_to_check = [
+          HOMEBREW_PREFIX,
+          HOMEBREW_REPOSITORY,
+          HOMEBREW_CELLAR,
+          HOMEBREW_TEMP,
+        ]
+        case_sensitive_dirs = dirs_to_check.select do |dir|
           # We select the dir as being case-sensitive if either the UPCASED or the
           # downcased variant is missing.
           # Of course, on a case-insensitive fs, both exist because the os reports so.
           # In the rare situation when the user has indeed a downcased and an upcased
           # dir (e.g. /TMP and /tmp) this check falsely thinks it is case-insensitive
-          # but we don't care beacuse: 1. there is more than one dir checked, 2. the
+          # but we don't care because: 1. there is more than one dir checked, 2. the
           # check is not vital and 3. we would have to touch files otherwise.
           upcased = Pathname.new(dir.to_s.upcase)
           downcased = Pathname.new(dir.to_s.downcase)
           dir.exist? && !(upcased.exist? && downcased.exist?)
-        end.map { |case_sensitive_dir| volumes.get_mounts(case_sensitive_dir) }.uniq
-        return if case_sensitive_vols.empty?
+        end
+        return if case_sensitive_dirs.empty?
+
+        volumes = Volumes.new
+        case_sensitive_vols = case_sensitive_dirs.map do |case_sensitive_dir|
+          volumes.get_mounts(case_sensitive_dir)
+        end
+        case_sensitive_vols.uniq!
+
         <<-EOS.undent
-        The filesystem on #{case_sensitive_vols.join(",")} appears to be case-sensitive.
-        The default OS X filesystem is case-insensitive. Please report any apparent problems.
-      EOS
+          The filesystem on #{case_sensitive_vols.join(",")} appears to be case-sensitive.
+          The default OS X filesystem is case-insensitive. Please report any apparent problems.
+        EOS
       end
 
       def __check_git_version
         # https://help.github.com/articles/https-cloning-errors
         `git --version`.chomp =~ /git version ((?:\d+\.?)+)/
+        return unless $1 && Version.new($1) < Version.new("1.7.10")
 
-        if $1 && Version.new($1) < Version.new("1.7.10")
-          git_upgrade_cmd = Formula["git"].any_version_installed? ? "upgrade" : "install"
-
-          <<-EOS.undent
-            An outdated version of Git was detected in your PATH.
-            Git 1.7.10 or newer is required to perform checkouts over HTTPS from GitHub.
-            Please upgrade: brew #{git_upgrade_cmd} git
-          EOS
-        end
+        git = Formula["git"]
+        git_upgrade_cmd = git.any_version_installed? ? "upgrade" : "install"
+        <<-EOS.undent
+          An outdated version of Git was detected in your PATH.
+          Git 1.7.10 or newer is required to perform checkouts over HTTPS from GitHub.
+          Please upgrade:
+            brew #{git_upgrade_cmd} git
+        EOS
       end
 
       def check_for_git
         if Utils.git_available?
           __check_git_version
-        else <<-EOS.undent
-        Git could not be found in your PATH.
-        Homebrew uses Git for several internal functions, and some formulae use Git
-        checkouts instead of stable tarballs. You may want to install Git:
-          brew install git
-        EOS
+        else
+          <<-EOS.undent
+            Git could not be found in your PATH.
+            Homebrew uses Git for several internal functions, and some formulae use Git
+            checkouts instead of stable tarballs. You may want to install Git:
+              brew install git
+          EOS
         end
       end
 
@@ -1006,18 +1059,18 @@ module Homebrew
         return unless Utils.git_available?
 
         autocrlf = HOMEBREW_REPOSITORY.cd { `git config --get core.autocrlf`.chomp }
+        return unless autocrlf == "true"
 
-        if autocrlf == "true" then <<-EOS.undent
-        Suspicious Git newline settings found.
+        <<-EOS.undent
+          Suspicious Git newline settings found.
 
-        The detected Git newline settings will cause checkout problems:
-          core.autocrlf = #{autocrlf}
+          The detected Git newline settings will cause checkout problems:
+            core.autocrlf = #{autocrlf}
 
-        If you are not routinely dealing with Windows-based projects,
-        consider removing these by running:
-        `git config --global core.autocrlf input`
+          If you are not routinely dealing with Windows-based projects,
+          consider removing these by running:
+            git config --global core.autocrlf input
         EOS
-        end
       end
 
       def check_git_origin
@@ -1025,24 +1078,26 @@ module Homebrew
 
         origin = Homebrew.git_origin
 
-        if origin.nil? then <<-EOS.undent
-          Missing git origin remote.
+        if origin.nil?
+          <<-EOS.undent
+            Missing git origin remote.
 
-          Without a correctly configured origin, Homebrew won't update
-          properly. You can solve this by adding the Homebrew remote:
-            cd #{HOMEBREW_REPOSITORY}
-            git remote add origin https://github.com/Homebrew/brew.git
+            Without a correctly configured origin, Homebrew won't update
+            properly. You can solve this by adding the Homebrew remote:
+              cd #{HOMEBREW_REPOSITORY}
+              git remote add origin https://github.com/Homebrew/brew.git
           EOS
-        elsif origin !~ /Homebrew\/brew(\.git)?$/ then <<-EOS.undent
-          Suspicious git origin remote found.
+        elsif origin !~ /Homebrew\/brew(\.git)?$/
+          <<-EOS.undent
+            Suspicious git origin remote found.
 
-          With a non-standard origin, Homebrew won't pull updates from
-          the main repository. The current git origin is:
-            #{origin}
+            With a non-standard origin, Homebrew won't pull updates from
+            the main repository. The current git origin is:
+              #{origin}
 
-          Unless you have compelling reasons, consider setting the
-          origin remote to point at the main repository, located at:
-            https://github.com/Homebrew/brew.git
+            Unless you have compelling reasons, consider setting the
+            origin remote to point at the main repository, located at:
+              https://github.com/Homebrew/brew.git
           EOS
         end
       end
@@ -1053,13 +1108,14 @@ module Homebrew
 
         autoconf = which("autoconf")
         safe_autoconfs = %w[/usr/bin/autoconf /Developer/usr/bin/autoconf]
-        unless autoconf.nil? || safe_autoconfs.include?(autoconf.to_s) then <<-EOS.undent
-        An "autoconf" in your path blocks the Xcode-provided version at:
-          #{autoconf}
+        return if autoconf.nil? || safe_autoconfs.include?(autoconf.to_s)
 
-        This custom autoconf may cause some Homebrew formulae to fail to compile.
+        <<-EOS.undent
+          An "autoconf" in your path blocks the Xcode-provided version at:
+            #{autoconf}
+
+          This custom autoconf may cause some Homebrew formulae to fail to compile.
         EOS
-        end
       end
 
       def __check_linked_brew(f)
@@ -1080,39 +1136,48 @@ module Homebrew
         linked = Formula.installed.select do |f|
           f.keg_only? && __check_linked_brew(f)
         end
-
         return if linked.empty?
+
         inject_file_list linked.map(&:full_name), <<-EOS.undent
-        Some keg-only formula are linked into the Cellar.
-        Linking a keg-only formula, such as gettext, into the cellar with
-        `brew link <formula>` will cause other formulae to detect them during
-        the `./configure` step. This may cause problems when compiling those
-        other formulae.
+          Some keg-only formula are linked into the Cellar.
+          Linking a keg-only formula, such as gettext, into the cellar with
+          `brew link <formula>` will cause other formulae to detect them during
+          the `./configure` step. This may cause problems when compiling those
+          other formulae.
 
-        Binaries provided by keg-only formulae may override system binaries
-        with other strange results.
+          Binaries provided by keg-only formulae may override system binaries
+          with other strange results.
 
-        You may wish to `brew unlink` these brews:
+          You may wish to `brew unlink` these brews:
         EOS
       end
 
       def check_for_other_frameworks
         # Other frameworks that are known to cause problems when present
-        %w[expat.framework libexpat.framework libcurl.framework].
-          map { |frmwrk| "/Library/Frameworks/#{frmwrk}" }.
-          select { |frmwrk| File.exist? frmwrk }.
-          map do |frmwrk|
-            <<-EOS.undent
-          #{frmwrk} detected
-          This can be picked up by CMake's build system and likely cause the build to
-          fail. You may need to move this file out of the way to compile CMake.
-          EOS
-          end.join
+        frameworks_to_check = %w[
+          expat.framework
+          libexpat.framework
+          libcurl.framework
+        ]
+        frameworks_found = frameworks_to_check.
+          map { |framework| "/Library/Frameworks/#{framework}" }.
+          select { |framework| File.exist? framework }
+        return if frameworks_found.empty?
+
+        inject_file_list frameworks_found, <<-EOS.undent
+          Some frameworks can be picked up by CMake's build system and likely
+          cause the build to fail. To compile CMake, you may wish to move these
+          out of the way:
+        EOS
       end
 
       def check_tmpdir
         tmpdir = ENV["TMPDIR"]
-        "TMPDIR #{tmpdir.inspect} doesn't exist." unless tmpdir.nil? || File.directory?(tmpdir)
+        return if tmpdir.nil? || File.directory?(tmpdir)
+
+        <<-EOS.undent
+          TMPDIR #{tmpdir.inspect} doesn't exist.
+        EOS
       end
 
       def check_missing_deps
@@ -1121,72 +1186,78 @@ module Homebrew
         Homebrew::Diagnostic.missing_deps(Formula.installed).each_value do |deps|
           missing.merge(deps)
         end
+        return if missing.empty?
 
-        if missing.any? then <<-EOS.undent
+        <<-EOS.undent
           Some installed formula are missing dependencies.
           You should `brew install` the missing dependencies:
-
-              brew install #{missing.sort_by(&:full_name) * " "}
+            brew install #{missing.sort_by(&:full_name) * " "}
 
           Run `brew missing` for more details.
         EOS
-        end
       end
 
       def check_git_status
         return unless Utils.git_available?
         HOMEBREW_REPOSITORY.cd do
-          unless `git status --untracked-files=all --porcelain -- Library/Homebrew/ 2>/dev/null`.chomp.empty?
-            <<-EOS.undent_________________________________________________________72
+          return if `git status --untracked-files=all --porcelain -- Library/Homebrew/ 2>/dev/null`.chomp.empty?
+        end
+
+        <<-EOS.undent
           You have uncommitted modifications to Homebrew
           If this is a surprise to you, then you should stash these modifications.
           Stashing returns Homebrew to a pristine state but can be undone
           should you later need to do so for some reason.
-              cd #{HOMEBREW_LIBRARY} && git stash && git clean -d -f
-          EOS
-          end
-        end
+            cd #{HOMEBREW_LIBRARY} && git stash && git clean -d -f
+        EOS
       end
 
       def check_for_enthought_python
-        if which "enpkg" then <<-EOS.undent
-        Enthought Python was found in your PATH.
-        This can cause build problems, as this software installs its own
-        copies of iconv and libxml2 into directories that are picked up by
-        other build systems.
+        return unless which "enpkg"
+
+        <<-EOS.undent
+          Enthought Python was found in your PATH.
+          This can cause build problems, as this software installs its own
+          copies of iconv and libxml2 into directories that are picked up by
+          other build systems.
         EOS
-        end
       end
 
       def check_for_library_python
-        if File.exist?("/Library/Frameworks/Python.framework") then <<-EOS.undent
-        Python is installed at /Library/Frameworks/Python.framework
+        return unless File.exist?("/Library/Frameworks/Python.framework")
 
-        Homebrew only supports building against the System-provided Python or a
-        brewed Python. In particular, Pythons installed to /Library can interfere
-        with other software installs.
+        <<-EOS.undent
+          Python is installed at /Library/Frameworks/Python.framework
+
+          Homebrew only supports building against the System-provided Python or a
+          brewed Python. In particular, Pythons installed to /Library can interfere
+          with other software installs.
         EOS
-        end
       end
 
       def check_for_old_homebrew_share_python_in_path
-        s = ""
+        message = ""
         ["", "3"].map do |suffix|
           if paths.include?((HOMEBREW_PREFIX/"share/python#{suffix}").to_s)
-            s += "#{HOMEBREW_PREFIX}/share/python#{suffix} is not needed in PATH.\n"
+            message += <<-EOS.undent
+              #{HOMEBREW_PREFIX}/share/python#{suffix} is not needed in PATH.
+            EOS
           end
         end
-        unless s.empty?
-          s += <<-EOS.undent
-          Formerly homebrew put Python scripts you installed via `pip` or `pip3`
-          (or `easy_install`) into that directory above but now it can be removed
-          from your PATH variable.
-          Python scripts will now install into #{HOMEBREW_PREFIX}/bin.
-          You can delete anything, except 'Extras', from the #{HOMEBREW_PREFIX}/share/python
-          (and #{HOMEBREW_PREFIX}/share/python3) dir and install affected Python packages
-          anew with `pip install --upgrade`.
-        EOS
+        unless message.empty?
+          message += <<-EOS.undent
+
+            Formerly homebrew put Python scripts you installed via `pip` or `pip3`
+            (or `easy_install`) into that directory above but now it can be removed
+            from your PATH variable.
+            Python scripts will now install into #{HOMEBREW_PREFIX}/bin.
+            You can delete anything, except 'Extras', from the #{HOMEBREW_PREFIX}/share/python
+            (and #{HOMEBREW_PREFIX}/share/python3) dir and install affected Python packages
+            anew with `pip install --upgrade`.
+          EOS
         end
+
+        message unless message.empty?
       end
 
       def check_for_bad_python_symlink
@@ -1194,11 +1265,12 @@ module Homebrew
         `python -V 2>&1` =~ /Python (\d+)\./
         # This won't be the right warning if we matched nothing at all
         return if $1.nil?
-        unless $1 == "2" then <<-EOS.undent
-        python is symlinked to python#{$1}
-        This will confuse build scripts and in general lead to subtle breakage.
+        return if $1 == "2"
+
+        <<-EOS.undent
+          python is symlinked to python#{$1}
+          This will confuse build scripts and in general lead to subtle breakage.
         EOS
-        end
       end
 
       def check_for_non_prefixed_coreutils
@@ -1227,13 +1299,14 @@ module Homebrew
       end
 
       def check_for_pydistutils_cfg_in_home
-        if File.exist? "#{ENV["HOME"]}/.pydistutils.cfg" then <<-EOS.undent
-        A .pydistutils.cfg file was found in $HOME, which may cause Python
-        builds to fail. See:
-          https://bugs.python.org/issue6138
-          https://bugs.python.org/issue4655
+        return unless File.exist? "#{ENV["HOME"]}/.pydistutils.cfg"
+
+        <<-EOS.undent
+          A .pydistutils.cfg file was found in $HOME, which may cause Python
+          builds to fail. See:
+            https://bugs.python.org/issue6138
+            https://bugs.python.org/issue4655
         EOS
-        end
       end
 
       def check_for_outdated_homebrew
@@ -1273,24 +1346,25 @@ module Homebrew
             true
           end
         end.map(&:basename)
-
         return if unlinked.empty?
+
         inject_file_list unlinked, <<-EOS.undent
-        You have unlinked kegs in your Cellar
-        Leaving kegs unlinked can lead to build-trouble and cause brews that depend on
-        those kegs to fail to run properly once built. Run `brew link` on these:
+          You have unlinked kegs in your Cellar
+          Leaving kegs unlinked can lead to build-trouble and cause brews that depend on
+          those kegs to fail to run properly once built. Run `brew link` on these:
         EOS
       end
 
       def check_xcode_license_approved
         # If the user installs Xcode-only, they have to approve the
         # license or no "xc*" tool will work.
-        if `/usr/bin/xcrun clang 2>&1` =~ /license/ && !$?.success? then <<-EOS.undent
+        return unless `/usr/bin/xcrun clang 2>&1` =~ /license/ && !$?.success?
+
+        <<-EOS.undent
           You have not agreed to the Xcode license.
           Builds will fail! Agree to the license by opening Xcode.app or running:
-              sudo xcodebuild -license
-          EOS
-        end
+            sudo xcodebuild -license
+        EOS
       end
 
       def check_for_latest_xquartz
@@ -1298,8 +1372,7 @@ module Homebrew
         return if MacOS::XQuartz.provided_by_apple?
 
         installed_version = Version.new(MacOS::XQuartz.version)
-        latest_version    = Version.new(MacOS::XQuartz.latest_version)
-
+        latest_version = Version.new(MacOS::XQuartz.latest_version)
         return if installed_version >= latest_version
 
         <<-EOS.undent
@@ -1310,13 +1383,13 @@ module Homebrew
       end
 
       def check_for_old_env_vars
-        if ENV["HOMEBREW_KEEP_INFO"]
-          <<-EOS.undent
+        return unless ENV["HOMEBREW_KEEP_INFO"]
+
+        <<-EOS.undent
           `HOMEBREW_KEEP_INFO` is no longer used
           info files are no longer deleted by default; you may
           remove this environment variable.
-          EOS
-        end
+        EOS
       end
 
       def check_for_pth_support
@@ -1324,6 +1397,7 @@ module Homebrew
         return unless homebrew_site_packages.directory?
         return if Language::Python.reads_brewed_pth_files?("python") != false
         return unless Language::Python.in_sys_path?("python", homebrew_site_packages)
+
         user_site_packages = Language::Python.user_site_packages "python"
         <<-EOS.undent
           Your default Python does not recognize the Homebrew site-packages
@@ -1331,7 +1405,6 @@ module Homebrew
           files will not be followed. This means you will not be able to import
           some modules after installing them with Homebrew, like wxpython. To fix
           this for the current user, you can run:
-
             mkdir -p #{user_site_packages}
             echo 'import site; site.addsitedir("#{homebrew_site_packages}")' >> #{user_site_packages}/homebrew.pth
         EOS
@@ -1348,14 +1421,16 @@ module Homebrew
         end
         cmd_map.reject! { |_cmd_name, cmd_paths| cmd_paths.size == 1 }
         return if cmd_map.empty?
-        s = "You have external commands with conflicting names.\n"
+
+        message = "You have external commands with conflicting names.\n"
         cmd_map.each do |cmd_name, cmd_paths|
-          s += inject_file_list cmd_paths, <<-EOS.undent
+          message += inject_file_list cmd_paths, <<-EOS.undent
 
             Found command `#{cmd_name}` in following places:
           EOS
         end
-        s
+
+        message
       end
 
       def all