Decouple DATA patches from the executing script

Library/Homebrew/build.rb

@@ -1,14 +1,9 @@
 # This script is loaded by formula_installer as a separate instance.
-# Rationale: Formula can use __END__, Formula can change ENV
 # Thrown exceptions are propogated back to the parent process over a pipe
 
 STD_TRAP = trap("INT") { exit! 130 } # no backtrace thanks
 
-at_exit do
-  # the whole of everything must be run in at_exit because the formula has to
-  # be the run script as __END__ must work for *that* formula.
-  main
-end
+at_exit { main }
 
 require 'global'
 require 'cxxstdlib'

Library/Homebrew/formula.rb

@@ -212,6 +212,8 @@ class Formula
   # any e.g. configure options for this package
   def options; [] end
 
+  # Deprecated
+  DATA = :DATA
   def patches; {} end
 
   # rarely, you don't want your library symlinked into the main prefix
@@ -577,6 +579,8 @@ class Formula
     active_spec.add_legacy_patches(patches)
     return if patchlist.empty?
 
+    active_spec.patches.grep(DATAPatch).each { |p| p.path = path }
+
     active_spec.patches.select(&:external?).each do |patch|
       patch.verify_download_integrity(patch.fetch)
     end

Library/Homebrew/formula_installer.rb

@@ -483,8 +483,6 @@ class FormulaInstaller
     # 1. formulae can modify ENV, so we must ensure that each
     #    installation has a pristine ENV when it starts, forking now is
     #    the easiest way to do this
-    # 2. formulae have access to __END__ the only way to allow this is
-    #    to make the formula script the executed script
     read, write = IO.pipe
     # I'm guessing this is not a good way to do this, but I'm no UNIX guru
     ENV['HOMEBREW_ERROR_PIPE'] = write.to_i.to_s

Library/Homebrew/patch.rb

@@ -5,13 +5,17 @@ require 'erb'
 module Patch
   def self.create(strip, io, &block)
     case strip
-    when :DATA, IO, StringIO
+    when :DATA
+      DATAPatch.new(:p1)
+    when IO, StringIO
       IOPatch.new(strip, :p1)
     when String
       IOPatch.new(StringIO.new(strip), :p1)
     when Symbol
       case io
-      when :DATA, IO, StringIO
+      when :DATA
+        DATAPatch.new(strip)
+      when IO, StringIO
         IOPatch.new(io, strip)
       when String
         IOPatch.new(StringIO.new(io), strip)
@@ -29,16 +33,15 @@ module Patch
     case list
     when Hash
       list
-    when Array, String, IO
+    when Array, String, :DATA
       { :p1 => list }
     else
       {}
     end.each_pair do |strip, urls|
-      urls = [urls] unless Array === urls
-      urls.each do |url|
+      Array(urls).each do |url|
         case url
-        when IO
-          patch = IOPatch.new(url, strip)
+        when :DATA
+          patch = DATAPatch.new(strip)
         else
           patch = LegacyPatch.new(strip, url)
         end
@@ -64,9 +67,7 @@ class IOPatch
   end
 
   def apply
-    @io = DATA if @io == :DATA
-    data = @io.read
-    data.gsub!("HOMEBREW_PREFIX", HOMEBREW_PREFIX)
+    data = contents.gsub("HOMEBREW_PREFIX", HOMEBREW_PREFIX)
     IO.popen("/usr/bin/patch -g 0 -f -#{strip}", "w") { |p| p.write(data) }
     raise ErrorDuringExecution, "Applying DATA patch failed" unless $?.success?
   ensure
@@ -75,11 +76,35 @@ class IOPatch
     @io = nil
   end
 
+  def contents
+    @io.read
+  end
+
   def inspect
     "#<#{self.class.name}: #{strip.inspect}>"
   end
 end
 
+class DATAPatch < IOPatch
+  attr_accessor :path
+
+  def initialize(strip)
+    @strip = strip
+    @path = nil
+  end
+
+  def contents
+    data = ""
+    path.open("rb") do |f|
+      begin
+        line = f.gets
+      end until line.nil? || /^__END__$/ === line
+      data << line while line = f.gets
+    end
+    data
+  end
+end
+
 class ExternalPatch
   attr_reader :resource, :strip
 

Library/Homebrew/test/test_patch.rb

@@ -36,13 +36,13 @@ class PatchTests < Homebrew::TestCase
 
   def test_create_DATA
     patch = Patch.create(:p0, :DATA)
-    assert_kind_of IOPatch, patch
+    assert_kind_of DATAPatch, patch
     assert_equal :p0, patch.strip
   end
 
   def test_create_DATA_without_strip
     patch = Patch.create(:DATA, nil)
-    assert_kind_of IOPatch, patch
+    assert_kind_of DATAPatch, patch
     assert_equal :p1, patch.strip
   end
 

Library/Homebrew/test/test_patching.rb

@@ -8,7 +8,7 @@ class PatchingTests < Homebrew::TestCase
   PATCH_A_CONTENTS = File.read "#{TEST_DIRECTORY}/patches/noop-a.diff"
   PATCH_B_CONTENTS = File.read "#{TEST_DIRECTORY}/patches/noop-b.diff"
 
-  def formula(&block)
+  def formula(*args, &block)
     super do
       url "file://#{TEST_DIRECTORY}/tarballs/testball-0.1.tbz"
       sha1 "482e737739d946b7c8cbaf127d9ee9c148b999f5"
@@ -138,4 +138,26 @@ class PatchingTests < Homebrew::TestCase
       end.brew { assert_patched 'libexec/noop' }
     end
   end
+
+  def test_patch_DATA_constant
+    shutup do
+      formula("test", Pathname.new(__FILE__).expand_path) do
+        def patches
+          Formula::DATA
+        end
+      end.brew { assert_patched "libexec/noop" }
+    end
+  end
 end
+
+__END__
+diff --git a/libexec/NOOP b/libexec/NOOP
+index bfdda4c..e08d8f4 100755
+--- a/libexec/NOOP
++++ b/libexec/NOOP
+@@ -1,2 +1,2 @@
+ #!/bin/bash
+-echo NOOP
+\ No newline at end of file
++echo ABCD
+\ No newline at end of file