Create proxy classes for "partial" X11 dependencies

When a formula's dependency tree contains more than one X11 dependency,
they are de-duplicated by comparing the min_version attribute. However,
this can result in broken dependency trees if one of the X11Dependency
objects was actually specified as e.g. `:libpng`.

In practice, this only matters when one or more of the dependencies has
additional metadata that makes it distinct from the rest, i.e. an
:optional or :recommended tag.

To combat this, make these special, "partial" X11 dependencies instances
of different classes so that they are not de-duped.

It will still be necessary, at the time when requirements are expanded
by the installer, to de-duplicate any remaining X11 dependencies after
applying the optional/recommended filters in order to avoid duplicated
modifications to the environment (as ENV.x11 is not idempotent).

c.f. Homebrew/homebrew#17369.

1 files changed, 67 insertions, 0 deletions

diff --git a/Library/Homebrew/test/test_x11_deps.rb b/Library/Homebrew/test/test_x11_deps.rb
new file mode 100644
index 000000000..c455d03d3
--- /dev/null
+++ b/Library/Homebrew/test/test_x11_deps.rb
@@ -0,0 +1,67 @@
+require 'testing_env'
+require 'requirements'
+require 'extend/set'
+
+class X11DependencyTests < Test::Unit::TestCase
+  def test_eql_instances_are_eql
+    x = X11Dependency.new
+    y = X11Dependency.new
+    assert x.eql?(y)
+    assert y.eql?(x)
+    assert x.hash == y.hash
+  end
+
+  def test_not_eql_when_hashes_differ
+    x = X11Dependency.new("foo")
+    y = X11Dependency.new
+    assert x.hash != y.hash
+    assert !x.eql?(y)
+    assert !y.eql?(x)
+  end
+
+  def test_proxy_for
+    x = X11Dependency::Proxy.for("libpng")
+    assert_instance_of X11Dependency::Proxy::Libpng, x
+    assert_kind_of X11Dependency, x
+  end
+
+  def test_proxy_eql_instances_are_eql
+    x = X11Dependency::Proxy.for("libpng")
+    y = X11Dependency::Proxy.for("libpng")
+    assert x.eql?(y)
+    assert y.eql?(x)
+    assert x.hash == y.hash
+  end
+
+  def test_proxy_not_eql_when_hashes_differ
+    x = X11Dependency::Proxy.for("libpng")
+    y = X11Dependency::Proxy.for("fontconfig")
+    assert x.hash != y.hash
+    assert !x.eql?(y)
+    assert !y.eql?(x)
+  end
+
+  def test_x_never_eql_to_proxy_x11_dep
+    x = X11Dependency.new("libpng")
+    p = X11Dependency::Proxy.for("libpng")
+    assert !x.eql?(p)
+    assert !p.eql?(x)
+  end
+end
+
+class X11DepCollectionTests < Test::Unit::TestCase
+  def setup
+    @set = ComparableSet.new
+  end
+
+  def test_x_can_coxist_with_proxy
+    @set << X11Dependency.new << X11Dependency::Proxy.for("libpng")
+    assert_equal 2, @set.count
+  end
+
+  def test_multiple_proxies_can_coexist
+    @set << X11Dependency::Proxy.for("libpng")
+    @set << X11Dependency::Proxy.for("fontconfig")
+    assert_equal 2, @set.count
+  end
+end