Manage Requirements using ComparableSet

ComparableSet only allows a single object of a given class,
choosing the object with the greatest value. This was mainly created
for Requirements, so that, e.g., two X11Dependencies of differing
strictness don't both end up in the same requirement set.

Fixes Homebrew/homebrew#15240.

1 files changed, 17 insertions, 3 deletions

diff --git a/Library/Homebrew/dependencies.rb b/Library/Homebrew/dependencies.rb
index 5d5b5ab0d..7c2ff7d1b 100644
--- a/Library/Homebrew/dependencies.rb
+++ b/Library/Homebrew/dependencies.rb
@@ -21,7 +21,7 @@ class DependencyCollector
 
   def initialize
     @deps = Dependencies.new
-    @requirements = Set.new
+    @requirements = ComparableSet.new
   end
 
   def add spec
@@ -196,6 +196,9 @@ end
 # This requirement is used to require an X11 implementation,
 # optionally with a minimum version number.
 class X11Dependency < Requirement
+  include Comparable
+  attr_reader :min_version
+
   def initialize min_version=nil
     @min_version = min_version
   end
@@ -217,9 +220,20 @@ class X11Dependency < Requirement
     ENV.x11
   end
 
-  def hash
-    "X11".hash
+  def <=> other
+    unless other.is_a? X11Dependency
+      raise TypeError, "expected X11Dependency"
+    end
+
+    if other.min_version.nil?
+      1
+    elsif @min_version.nil?
+      -1
+    else
+      @min_version <=> other.min_version
+    end
   end
+
 end