Check deps of satisfied deps

Library/Homebrew/dependency.rb

@@ -71,8 +71,11 @@ class Dependency
     # optionals and recommendeds based on what the dependent has asked for.
     def expand(dependent, &block)
       deps = dependent.deps.map do |dep|
-        if prune?(dependent, dep, &block)
+        case action(dependent, dep, &block)
+        when :prune
           next
+        when :skip
+          expand(dep.to_formula, &block)
         else
           expand(dep.to_formula, &block) << dep
         end
@@ -81,8 +84,8 @@ class Dependency
       merge_repeats(deps)
     end
 
-    def prune?(dependent, dep, &block)
-      catch(:prune) do
+    def action(dependent, dep, &block)
+      catch(:action) do
         if block_given?
           yield dependent, dep
         elsif dep.optional? || dep.recommended?
@@ -93,7 +96,11 @@ class Dependency
 
     # Used to prune dependencies when calling expand with a block.
     def prune
-      throw(:prune, true)
+      throw(:action, :prune)
+    end
+
+    def skip
+      throw(:action, :skip)
     end
 
     def merge_repeats(deps)

Library/Homebrew/formula_installer.rb

@@ -178,7 +178,7 @@ class FormulaInstaller
         elsif dep.build? && install_bottle?(dependent)
           Dependency.prune
         elsif dep.satisfied?
-          Dependency.prune
+          Dependency.skip
         elsif dep.installed?
           raise UnsatisfiedDependencyError.new(f, dep)
         end

Library/Homebrew/test/test_dependency_expansion.rb

@@ -82,4 +82,17 @@ class DependencyExpansionTests < Test::Unit::TestCase
 
     assert_equal %w{option}, Dependency.expand(@f).first.tags
   end
+
+  def test_skip_skips_parent_but_yields_children
+    f = stub(:deps => [
+      build_dep(:foo, [], [@bar, @baz]),
+      build_dep(:foo, [], [@baz]),
+    ])
+
+    deps = Dependency.expand(f) do |dependent, dep|
+      Dependency.skip if %w{foo qux}.include? dep.name
+    end
+
+    assert_equal [@bar, @baz], deps
+  end
 end