Install: add BuildToolsError and BuildFlagsError

Add these new errors, and guards in formula installation and
cmd/{,un,re}install to match, move can_build? to the MacOS module,
flatten conditions, remove redundant can_build? check

reinstate removed (doctor) check

Library/Homebrew/cmd/install.rb

@@ -38,6 +38,14 @@ module Homebrew
         end
       end
 
+      # if the user's flags will prevent bottle only-installations when no
+      # developer tools are available, we need to stop them early on
+      if !MacOS.can_build?
+        bf = ARGV.collect_build_flags
+
+        raise BuildFlagsError.new(bf) if !bf.empty?
+      end
+
       ARGV.formulae.each do |f|
         # head-only without --HEAD is an error
         if !ARGV.build_head? && f.stable.nil? && f.devel.nil?
@@ -129,6 +137,9 @@ module Homebrew
     # when one is no longer required
     checks = Checks.new
     %w[
+      check_for_unsupported_osx
+      check_for_bad_install_name_tool
+      check_for_installed_developer_tools
       check_xcode_license_approved
       check_for_osx_gcc_installer
     ].each do |check|
@@ -157,12 +168,7 @@ module Homebrew
   def perform_preinstall_checks
     check_ppc
     check_writable_install_location
-    if MacOS::Xcode.installed?
+    check_xcode if MacOS::Xcode.installed?
-      check_xcode
-    else
-      opoo "You have not installed Xcode."
-      puts "Bottles may install correctly, but builds will fail!"
-    end
     check_cellar
   end
 

Library/Homebrew/cmd/reinstall.rb

@@ -2,6 +2,14 @@ require "formula_installer"
 
 module Homebrew
   def reinstall
+    if !MacOS.can_build?
+      bf = ARGV.collect_build_flags
+
+      if !bf.empty?
+        raise BuildFlagsError.new(bf)
+      end
+    end
+
     ARGV.resolved_formulae.each { |f| reinstall_formula(f) }
   end
 

Library/Homebrew/cmd/upgrade.rb

@@ -3,6 +3,14 @@ require "cmd/outdated"
 
 module Homebrew
   def upgrade
+    if !MacOS.can_build?
+      bf = ARGV.collect_build_flags
+
+      if !bf.empty?
+        raise BuildFlagsError.new(bf)
+      end
+    end
+
     Homebrew.perform_preinstall_checks
 
     if ARGV.named.empty?

Library/Homebrew/exceptions.rb

@@ -226,6 +226,100 @@ class BuildError < RuntimeError
   end
 end
 
+# raised by FormulaInstaller.check_dependencies_bottled and
+# FormulaInstaller.install if the formula or its dependencies are not bottled
+# and are being installed on a system without necessary build tools
+class BuildToolsError < RuntimeError
+  def initialize(formulae)
+    if formulae.length > 1
+      formula_text = "formulae"
+      package_text = "binary packages"
+    else
+      formula_text = "formula"
+      package_text = "a binary package"
+    end
+
+    if MacOS.version >= "10.10"
+      xcode_text = <<-EOS.undent
+        To continue, you must install Xcode from the App Store,
+              or the CLT by running:
+                xcode-select --install
+      EOS
+    elsif MacOS.version == "10.9"
+      xcode_text = <<-EOS.undent
+        To continue, you must install Xcode from:
+                https://developer.apple.com/downloads/
+              or the CLT by running:
+                xcode-select --install
+      EOS
+    elsif MacOS.version >= "10.7"
+      xcode_text = <<-EOS.undent
+        To continue, you must install Xcode or the CLT from:
+                https://developer.apple.com/downloads/
+      EOS
+    else
+      xcode_text = <<-EOS.undent
+        To continue, you must install Xcode from:
+                https://developer.apple.com/downloads/
+      EOS
+    end
+
+    super <<-EOS.undent
+      The following #{formula_text}:
+        #{formulae.join(', ')}
+      cannot be installed as a #{package_text} and must be built from source.
+      #{xcode_text}
+    EOS
+  end
+end
+
+# raised by Homebrew.install, Homebrew.reinstall, and Homebrew.upgrade
+# if the user passes any flags/environment that would case a bottle-only
+# installation on a system without build tools to fail
+class BuildFlagsError < RuntimeError
+  def initialize(flags)
+    if flags.length > 1
+      flag_text = "flags"
+      require_text = "require"
+    else
+      flag_text = "flag"
+      require_text = "requires"
+    end
+
+    if MacOS.version >= "10.10"
+      xcode_text = <<-EOS.undent
+        or install Xcode from the App Store, or the CLT by running:
+                xcode-select --install
+      EOS
+    elsif MacOS.version == "10.9"
+      xcode_text = <<-EOS.undent
+        or install Xcode from:
+                https://developer.apple.com/downloads/
+              or the CLT by running:
+                xcode-select --install
+      EOS
+    elsif MacOS.version >= "10.7"
+      xcode_text = <<-EOS.undent
+        or install Xcode or the CLT from:
+                https://developer.apple.com/downloads/
+      EOS
+    else
+      xcode_text = <<-EOS.undent
+        or install Xcode from:
+                https://developer.apple.com/downloads/
+      EOS
+    end
+
+    super <<-EOS.undent
+      The following #{flag_text}:
+        #{flags.join(', ')}
+      #{require_text} building tools, but none are installed.
+      Either remove the #{flag_text} to attempt bottle installation,
+      #{xcode_text}
+    EOS
+  end
+end
+
 # raised by CompilerSelector if the formula fails with all of
 # the compilers available on the user's system
 class CompilerSelectionError < RuntimeError

Library/Homebrew/extend/ARGV.rb

@@ -200,6 +200,19 @@ module HomebrewArgvExtension
     value "env"
   end
 
+  # collect any supplied build flags into an array for reporting
+  def collect_build_flags
+    build_flags = []
+
+    build_flags << '--HEAD' if build_head?
+    build_flags << '--universal' if build_universal?
+    build_flags << '--32-bit' if build_32_bit?
+    build_flags << '--build-bottle' if build_bottle?
+    build_flags << '--build-from-source' if build_from_source?
+
+    build_flags
+  end
+
   private
 
   def spec(default = :stable)

Library/Homebrew/formula_installer.rb

@@ -147,6 +147,10 @@ class FormulaInstaller
 
     check_conflicts
 
+    if !pour_bottle? && !MacOS.can_build?
+      raise BuildToolsError.new([formula])
+    end
+
     if !ignore_deps?
       deps = compute_dependencies
       check_dependencies_bottled(deps) if pour_bottle?

Library/Homebrew/os/mac.rb

@@ -52,6 +52,10 @@ module OS
       end
     end
 
+    def can_build?
+      Xcode.installed? || CLT.installed?
+    end
+
     def active_developer_dir
       @active_developer_dir ||= Utils.popen_read("/usr/bin/xcode-select", "-print-path").strip
     end