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.

1 files changed, 16 insertions, 15 deletions

diff --git a/bin/brew b/bin/brew
index ba7080290..6ce18a4ac 100755
--- a/bin/brew
+++ b/bin/brew
@@ -95,20 +95,24 @@ 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|
-          if f.installed? and not ARGV.force?
-            message = "Formula already installed: #{f.prefix}"
-            if ARGV.formulae.count > 1
-              opoo message
-            else
-              puts message # if only one is being installed a warning looks severe
-            end
-            next
+      fae = ARGV.formulae.reject do |f|
+        if f.installed? and not ARGV.force?
+          message = "Formula already installed: #{f.prefix}"
+          if ARGV.formulae.count > 1
+            opoo message
+          else
+            puts message # if only one is being installed a warning looks severe
           end
+          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}..."