[Specification] support for weak frameworks.

Closes #263

Gemfile.lock

 GIT
   remote: git://github.com/CocoaPods/Xcodeproj.git
-  revision: 2da2c3688dfd240b376f671e8e6525ba28729f38
+  revision: 88c230a58fc7a0a9f850bc2cb929625345804aef
   specs:
     xcodeproj (0.2.3)
       activesupport (~> 3.2.6)
@@ -74,7 +74,7 @@ GEM
       ffi (>= 0.5.0)
     redcarpet (2.1.1)
     slop (2.4.4)
-    vcr (2.2.2)
+    vcr (2.2.3)
     webmock (1.8.7)
       addressable (>= 2.2.7)
       crack (>= 0.1.7)

lib/cocoapods/specification.rb

@@ -44,6 +44,7 @@ module Pod
           preserve_paths
           exclude_header_search_paths
           frameworks
+          weak_frameworks
           libraries
           dependencies
           compiler_flags ].each do |attr|
@@ -127,6 +128,8 @@ module Pod
           xcconfig=
           framework=
           frameworks=
+          weak_framework=
+          weak_frameworks=
           library=
           libraries=
           compiler_flags=
@@ -240,11 +243,13 @@ module Pod
     pltf_chained_attr_accessor  :preserve_paths,              lambda {|value, current| pattern_list(value) } # Paths that should not be cleaned
     pltf_chained_attr_accessor  :exclude_header_search_paths, lambda {|value, current| pattern_list(value) } # Headers to be excluded from being added to search paths (RestKit)
     pltf_chained_attr_accessor  :frameworks,                  lambda {|value, current| (current << value).flatten }
+    pltf_chained_attr_accessor  :weak_frameworks,             lambda {|value, current| (current << value).flatten }
     pltf_chained_attr_accessor  :libraries,                   lambda {|value, current| (current << value).flatten }
 
     alias_method :resource=,        :resources=
     alias_method :preserve_path=,   :preserve_paths=
     alias_method :framework=,       :frameworks=
+    alias_method :weak_framework=,  :weak_frameworks=
     alias_method :library=,         :libraries=
 
     # @!method header_dir=
@@ -271,9 +276,11 @@ module Pod
     platform_attr_writer :xcconfig, lambda {|value, current| current.tap { |c| c.merge!(value) } }
 
     def xcconfig
-      raw_xconfig.dup.
-        tap { |x| x.libraries.merge  libraries }.
-        tap { |x| x.frameworks.merge frameworks }
+      result = raw_xconfig.dup
+      result.libraries.merge(libraries)
+      result.frameworks.merge(frameworks)
+      result.weak_frameworks.merge(weak_frameworks)
+      result
     end
 
     def raw_xconfig

spec/unit/specification_spec.rb

@@ -79,6 +79,13 @@ describe "A Pod::Specification loaded from a podspec" do
                          '-framework SystemConfiguration' }
   end
 
+  it "has a shortcut to add weak frameworks to the xcconfig" do
+    @spec.weak_frameworks = 'Twitter'
+    @spec.activate_platform(:ios).xcconfig.should == {
+      "OTHER_LDFLAGS"=>"-framework SystemConfiguration -weak_frameworks Twitter"
+    }
+  end
+
   it "has a shortcut to add libraries to the xcconfig" do
     @spec.libraries = 'z', 'xml2'
     @spec.activate_platform(:ios).xcconfig.should == {
@@ -293,6 +300,7 @@ describe "A Pod::Specification subspec" do
         fss.ios.source_files  = 'subspec_ios.m'
         fss.osx.source_files  = 'subspec_osx.m'
         fss.framework         = 'CoreGraphics'
+        fss.weak_framework    = 'Twitter'
         fss.library           = 'z'
 
         fss.subspec 'SecondSubSpec' do |sss|
@@ -428,18 +436,24 @@ describe "A Pod::Specification subspec" do
     @subsubspec.frameworks.should == %w[ CoreData CoreGraphics ]
   end
 
+  it "resolves the weak frameworks correctly" do
+    @spec.activate_platform(:ios)
+    @spec.weak_frameworks.should       == %w[  ]
+    @subspec.weak_frameworks.should    == %w[ Twitter ]
+  end
+
   it "resolves the xcconfig" do
     @spec.activate_platform(:ios)
     @spec.xcconfig = { 'OTHER_LDFLAGS' => "-Wl,-no_compact_unwind" }
 
     @spec.xcconfig.should       == {"OTHER_LDFLAGS"=>"-Wl,-no_compact_unwind -lxml -framework CoreData"}
-    @subspec.xcconfig.should    == {"OTHER_LDFLAGS"=>"-Wl,-no_compact_unwind -lxml -lz -framework CoreData -framework CoreGraphics"}
-    @subsubspec.xcconfig.should == {"OTHER_LDFLAGS"=>"-Wl,-no_compact_unwind -lxml -lz -framework CoreData -framework CoreGraphics"}
+    @subspec.xcconfig.should    == {"OTHER_LDFLAGS"=>"-Wl,-no_compact_unwind -lxml -lz -framework CoreData -framework CoreGraphics -weak_frameworks Twitter"}
+    @subsubspec.xcconfig.should == {"OTHER_LDFLAGS"=>"-Wl,-no_compact_unwind -lxml -lz -framework CoreData -framework CoreGraphics -weak_frameworks Twitter"}
 
     @subsubspec.xcconfig = { 'HEADER_SEARCH_PATHS' => '$(SDKROOT)/usr/include/libxml2' }
 
     @spec.xcconfig.should       == {"OTHER_LDFLAGS"=>"-Wl,-no_compact_unwind -lxml -framework CoreData"}
-    @subsubspec.xcconfig.should == {"OTHER_LDFLAGS"=>"-Wl,-no_compact_unwind -lxml -lz -framework CoreData -framework CoreGraphics", "HEADER_SEARCH_PATHS"=>"$(SDKROOT)/usr/include/libxml2"}
+    @subsubspec.xcconfig.should == {"OTHER_LDFLAGS"=>"-Wl,-no_compact_unwind -lxml -lz -framework CoreData -framework CoreGraphics -weak_frameworks Twitter", "HEADER_SEARCH_PATHS"=>"$(SDKROOT)/usr/include/libxml2"}
   end
 end