Improve python tests for brew bots

Allow `build.with?` and similar methods to be used during the test
phase. The BuildOptions (`build`) are initialized with the
`Tab.used_options` unless explicitly overwritten on the command line.

So basically `build.with?` works in `def install` and in `test do` as
one would naively expect. (For the test, gramatically it should be
`built.with?` but who cares)

If a formula was installed `--with-python`, now the tests are also
run `--with-python`. This enables us to use the `python do ... end` in
a meaningful manner.

Using `python do ... end` blocks for the tests, because the bot.brew.sh has
system python per default and we need to set the PYTHONPATH for the test.
Potentially to different values for Python 2.x and 3.x.

Library/Homebrew/build_options.rb

@@ -100,13 +100,26 @@ class BuildOptions
   # implicit_options are needed because `depends_on 'spam' => 'with-stuff'`
   # complains if 'spam' has stuff as default and only defines `--without-stuff`.
   def implicit_options
-    implicit = unused_options.map do |o|
-      if o.name =~ /^with-(.+)$/ && without?($1)
-        Option.new("without-#{$1}")  # we lose the description, but that's ok
-      elsif o.name =~ /^without-(.+)$/ && with?($1)
-        Option.new("with-#{$1}")
-      end
+    implicit = unused_options.map do |option|
+      opposite_of option unless has_opposite_of? option
     end.compact
     Options.new(implicit)
   end
+
+  def has_opposite_of? option
+    true if args.include? opposite_of option
+  end
+
+  def opposite_of option
+    option = Option.new option
+    if option.name =~ /^with-(.+)$/
+      Option.new("without-#{$1}")
+    elsif option.name =~ /^without-(.+)$/
+      Option.new("with-#{$1}")
+    elsif option.name =~ /^enable-(.+)$/
+      Option.new("disable-#{$1}")
+    elsif option.name =~ /^disable-(.+)$/
+      Option.new("enable-#{$1}")
+    end
+  end
 end

Library/Homebrew/formula.rb

@@ -515,6 +515,9 @@ class Formula
   def test
     require 'test/unit/assertions'
     extend(Test::Unit::Assertions)
+    # Adding the used options allows us to use `build.with?` inside of tests
+    tab = Tab.for_name(name)
+    tab.used_options.each { |opt| build.args << opt unless build.has_opposite_of? opt }
     ret = nil
     mktemp do
       @testpath = Pathname.pwd

Library/Homebrew/python_helper.rb

@@ -16,11 +16,11 @@
 def python_helper(options={:allowed_major_versions => [2, 3]}, &block)
   if !block_given? and !@current_python.nil?
     # We are already inside of a `python do ... end` block, so just return
-    # the current_python or false if the version.major is not allowed.
+    # the current_python or nil if the version.major is not allowed.
     if options[:allowed_major_versions].include?(@current_python.version.major)
       return @current_python
     else
-      return false
+      return nil
     end
   end
 
@@ -42,7 +42,7 @@ def python_helper(options={:allowed_major_versions => [2, 3]}, &block)
   end
 
   # Allow to use an else-branch like so: `if python do ... end; else ... end`.
-  return false if filtered_python_reqs.empty?
+  return nil if filtered_python_reqs.empty?
 
   # Sort by version, so the older 2.x will be used first and if no
   # block_given? then 2.x is preferred because it is returned.

Library/Homebrew/test/test_build_options.rb

@@ -1,9 +1,9 @@
-require 'testing_env'
+  require 'testing_env'
 require 'build_options'
 
 class BuildOptionsTests < Test::Unit::TestCase
   def setup
-    args = %w{--with-foo --with-bar --without-qux}
+    args = %w{--with-foo --with-bar --without-qux} # args fake the command line
     @build = BuildOptions.new(args)
     @build.add("with-foo")
     @build.add("with-bar")
@@ -44,7 +44,7 @@ class BuildOptionsTests < Test::Unit::TestCase
   end
 
   def test_implicit_options
-    # --without-baz is not explicitly specified on the command line
+    # --without-baz is not explicitly specified on the command line (i.e. args)
     # therefore --with-baz should be implicitly assumed:
     assert @build.implicit_options.include?("--with-baz")
     # But all these should not be in the implict_options:
@@ -53,4 +53,18 @@ class BuildOptionsTests < Test::Unit::TestCase
     assert !@build.implicit_options.include?("--without-bar")
     assert !@build.implicit_options.include?("--with-qux")
   end
+
+  def test_opposite_of
+    assert @build.opposite_of(Option.new("with-foo")) == Option.new("without-foo")
+    assert @build.opposite_of("without-foo") == Option.new("with-foo")
+    assert @build.opposite_of(Option.new("enable-spam")) == Option.new("disable-spam")
+    assert @build.opposite_of("disable-beer") == Option.new("enable-beer")
+  end
+
+  def test_has_opposite_of?
+    assert @build.has_opposite_of?("--without-foo")
+    assert @build.has_opposite_of?(Option.new("--with-qux"))
+    assert !@build.has_opposite_of?("--without-qux")
+    assert !@build.has_opposite_of?("--without-nonexisting")
+  end
 end