Merge repeated deps with differing options

When expanding dependencies, repeated deps are treated as equal and all
but the first are discarded when #uniq is called on the resulting array.
However, they may have different sets of options attached, so we cannot
assume they are the same.

After the initial expansion, we group them by name and then create a new
Dependency object for each name, merging the options from each group.

Fixes Homebrew/homebrew#20335.

Library/Homebrew/dependency.rb

@@ -70,13 +70,15 @@ class Dependency
     # The default filter, which is applied when a block is not given, omits
     # optionals and recommendeds based on what the dependent has asked for.
     def expand(dependent, &block)
-      dependent.deps.map do |dep|
+      deps = dependent.deps.map do |dep|
         if prune?(dependent, dep, &block)
           next
         else
           expand(dep.to_formula, &block) << dep
         end
-      end.flatten.compact.uniq
+      end.flatten.compact
+
+      merge_repeats(deps)
     end
 
     def prune?(dependent, dep, &block)
@@ -93,5 +95,13 @@ class Dependency
     def prune
       throw(:prune, true)
     end
+
+    def merge_repeats(deps)
+      grouped = deps.group_by(&:name)
+
+      deps.uniq.map do |dep|
+        new(dep.name, grouped.fetch(dep.name).map(&:tags).flatten)
+      end
+    end
   end
 end

Library/Homebrew/test/test_dependency_expansion.rb

@@ -2,8 +2,8 @@ require 'testing_env'
 require 'dependency'
 
 class DependencyExpansionTests < Test::Unit::TestCase
-  def build_dep(name, deps=[])
-    dep = Dependency.new(name.to_s)
+  def build_dep(name, tags=[], deps=[])
+    dep = Dependency.new(name.to_s, tags)
     dep.stubs(:to_formula).returns(stub(:deps => deps))
     dep
   end
@@ -58,4 +58,12 @@ class DependencyExpansionTests < Test::Unit::TestCase
     @f = stub(:deps => @deps, :build => stub(:with? => true))
     assert_equal @deps, Dependency.expand(@f)
   end
+
+  def test_merges_repeated_deps_with_differing_options
+    @foo2 = build_dep(:foo, ['option'])
+    @baz2 = build_dep(:baz, ['option'])
+    @deps << @foo2 << @baz2
+    deps = [@foo2, @bar, @baz2, @qux]
+    assert_equal deps, Dependency.expand(@f)
+  end
 end