Extract tag and checksum selection from DSL method

Library/Homebrew/software_spec.rb

@@ -47,7 +47,7 @@ class SoftwareSpec
   end
 
   def bottled?
-    bottle_specification.fully_specified?
+    bottle_specification.tag?(bottle_tag)
   end
 
   def bottle &block
@@ -124,16 +124,19 @@ class Bottle
     @name = f.name
     @resource = Resource.new
     @resource.owner = f
+
+    checksum, tag = spec.checksum_for(bottle_tag)
+
     @resource.url = bottle_url(
       spec.root_url,
       :name => f.name,
       :version => f.pkg_version,
       :revision => spec.revision,
-      :tag => spec.current_tag
+      :tag => tag
     )
     @resource.download_strategy = CurlBottleDownloadStrategy
     @resource.version = f.pkg_version
-    @resource.checksum = spec.checksum
+    @resource.checksum = checksum
     @prefix = spec.prefix
     @cellar = spec.cellar
     @revision = spec.revision
@@ -146,7 +149,7 @@ end
 
 class BottleSpecification
   attr_rw :root_url, :prefix, :cellar, :revision
-  attr_reader :current_tag, :checksum, :collector
+  attr_reader :checksum, :collector
 
   def initialize
     @revision = 0
@@ -156,23 +159,21 @@ class BottleSpecification
     @collector = BottleCollector.new
   end
 
-  def fully_specified?
-    checksum && !checksum.empty?
+  def tag?(tag)
+    !!collector.fetch_bottle_for(tag)
   end
 
   # Checksum methods in the DSL's bottle block optionally take
   # a Hash, which indicates the platform the checksum applies on.
   Checksum::TYPES.each do |cksum|
-    class_eval <<-EOS, __FILE__, __LINE__ + 1
-      def #{cksum}(val)
-        digest, tag = val.shift
-        collector.add(Checksum.new(:#{cksum}, digest), tag)
+    define_method(cksum) do |val|
+      digest, tag = val.shift
+      collector.add(Checksum.new(cksum, digest), tag)
+    end
+  end
 
-        cksum, current_tag = collector.fetch_bottle_for(bottle_tag)
-        @checksum = cksum if cksum
-        @current_tag = current_tag if cksum
-      end
-    EOS
+  def checksum_for(tag)
+    collector.fetch_bottle_for(tag)
   end
 
   def checksums