Dependency resolution

Specify dependencies in your formula's deps function. You can return an Array,
String or Hash, eg:

    def deps
      { :optional => 'libogg', :required => %w[flac sdl], :recommended => 'cmake' }
    end

Note currently the Hash is flattened and qualifications are ignored. If you
only return an Array or String, the qualification is assumed to be :required.

Other packaging systems have problems when it comes to packages requiring a
specific version of a package, or some patches that may not work well with
other software. With Homebrew we have some options:

1.  If the formula is vanilla but an older version we can cherry-pick the old
    version and install it in the Cellar in parallel, but just not symlink it
    into /usr/local while forcing the formula that depends on it to link to
    that one and not any other versions of it.
2.  If the dependency requires patches then we shouldn't install this for use
    by any other tools, (I guess this needs to be decided on a per-situation
    basis). It can be installed into the parent formula's prefix, and not
    symlinked into /usr/local. In this case the dependency's Formula
    derivation should be saved in the parent formula's file (check git or
    flac for an example of this).

Both the above can be done currently with hacks, so I'll flesh out a proper
way sometime this week.

Library/Homebrew/brew.h.rb

@@ -144,6 +144,33 @@ def clean f
 end
 
 
+# NOTE this is ugly code, and inefficient too, and can have infinite cycles
+# I have no time currently to improve it, feel free to submit a more elegant
+# solution. Thanks! --mxcl
+def expand_deps fae
+  deps = []
+  fae.each do |f|
+    case f.deps
+    when String, Array
+      f.deps.each do |name|
+        f = Formula.factory name
+        deps << expand_deps(f) if f.deps # hideous inefficient
+        deps << f
+      end
+    when Hash
+      # TODO implement optional and recommended
+      names = []
+      f.deps.each_value {|v| names << v}
+      ff=names.flatten.collect {|name| Formula.factory name}
+      deps << expand_deps(ff)
+    end
+    deps << f
+  end
+  # TODO much more efficient to use a set and not recurse stuff already done
+  return deps.flatten.uniq
+end
+
+
 def install f
   f.brew do
     if ARGV.flag? '--interactive'

Library/Homebrew/unittest.rb

@@ -41,7 +41,8 @@ class MostlyAbstractFormula <Formula
 end
 
 class TestBall <Formula
-  def initialize
+  # name parameter required for some Formula::factory
+  def initialize name=nil
     @url="file:///#{Pathname.new(ABS__FILE__).parent.realpath}/testball-0.1.tbz"
     super "testball"
   end
@@ -98,9 +99,13 @@ def nostdout
 end
 
 module ExtendArgvPlusYeast
-  def stick_an_arg_in_thar
+  def reset
     @named=nil
-    unshift 'foo'
+    @formulae=nil
+    @kegs=nil
+    while ARGV.count > 0
+      ARGV.shift
+    end
   end
 end
 ARGV.extend ExtendArgvPlusYeast
@@ -347,8 +352,9 @@ class BeerTasting <Test::Unit::TestCase
   end
 
   def test_no_ARGV_dupes
-    ARGV.unshift'foo'
-    ARGV.unshift'foo'
+    ARGV.reset
+    ARGV.unshift 'foo'
+    ARGV.unshift 'foo'
     n=0
     ARGV.named.each{|arg| n+=1 if arg == 'foo'}
     assert_equal 1, n
@@ -360,9 +366,10 @@ class BeerTasting <Test::Unit::TestCase
     assert_raises(UsageError) { ARGV.kegs }
     assert ARGV.named_empty?
     
-    (HOMEBREW_CELLAR+'foo'+'0.1').mkpath
+    (HOMEBREW_CELLAR+'mxcl'+'10.0').mkpath
     
-    ARGV.stick_an_arg_in_thar
+    ARGV.reset
+    ARGV.unshift 'mxcl'
     assert_equal 1, ARGV.named.length
     assert_equal 1, ARGV.kegs.length
     assert_raises(FormulaUnavailableError) { ARGV.formulae }
@@ -395,7 +402,7 @@ class BeerTasting <Test::Unit::TestCase
     nostdout do
       assert_nothing_raised do
         f=TestBall.new
-        make 'http://example.com/testball-0.1.tbz'
+        make f.url
         info f.name
         clean f
         prune

bin/brew

@@ -95,10 +95,7 @@ begin
         raise "We cannot find a c compiler, have you installed the latest Xcode?"
       end
 
-      require 'beer_events'
-      
-      watch_out_for_spill do
-        ARGV.formulae.each do |f|
+      fae = ARGV.formulae.reject do |f|
         if f.installed? and not ARGV.force?
           message = "Formula already installed: #{f.prefix}"
           if ARGV.formulae.count > 1
@@ -106,9 +103,16 @@ begin
           else
             puts message # if only one is being installed a warning looks severe
           end
-            next
+          true
+        end
       end
 
+      fae=expand_deps ARGV.formulae
+
+      require 'beer_events'
+
+      watch_out_for_spill do
+        fae.each do |f|
           # we need to ensure a pristine ENV for each process or the formula
           # will start with the ENV from the previous build
           pid=fork
@@ -162,9 +166,6 @@ begin
     when 'unlink'
       ARGV.kegs.each {|keg| puts "#{keg.unlink} links removed for #{keg}"}
 
-    when 'unlink'
-      ARGV.kegs.each {|keg| puts "#{keg.unlink} links removed for #{keg}"}
-
     when 'rm', 'uninstall', 'remove'
       ARGV.kegs.each do |keg|
         puts "Uninstalling #{keg}..."