Check if dependencies match the platform specified in the Podfile.

lib/cocoapods/resolver.rb

@@ -12,13 +12,26 @@ module Pod
 
     def find_dependency_sets(specification)
       specification.dependencies.each do |dependency|
-        set = Source.search(dependency)
+        set = find_dependency_set(dependency)
         set.required_by(specification)
         unless @sets.include?(set)
+          validate_platform!(set)
           @sets << set
           find_dependency_sets(set.specification)
         end
       end
     end
+
+    def find_dependency_set(dependency)
+      Source.search(dependency)
+    end
+
+    def validate_platform!(set)
+      spec = set.specification
+      unless spec.any_platform? || spec.platform == @specification.platform
+        raise Informative, "The platform required by the Podfile (:#{@specification.platform}) " \
+                           "does not match that of #{spec} (:#{spec.platform})"
+      end
+    end
   end
 end

spec/unit/resolver_spec.rb

 require File.expand_path('../../spec_helper', __FILE__)
 
+class StubbedSet < Pod::Specification::Set
+  attr_accessor :stub_platform
+
+  def specification
+    spec = super
+    spec.platform = @stub_platform
+    spec
+  end
+end
+
+class StubbedResolver < Pod::Resolver
+  attr_accessor :stub_platform
+
+  def find_dependency_set(dependency)
+    set = StubbedSet.new(super.pod_dir)
+    set.stub_platform = @stub_platform
+    set
+  end
+end
+
 describe "Pod::Resolver" do
   before do
     fixture('spec-repos/master') # ensure the archive is unpacked
@@ -18,5 +38,32 @@ describe "Pod::Resolver" do
     resolver = Pod::Resolver.new(Pod::Spec.new { |s| s.dependency 'ASIWebPageRequest' })
     resolver.resolve.sort_by(&:name).should == sets.sort_by(&:name)
   end
+
+  it "does not raise if all dependencies match the platform of the root spec (Podfile)" do
+    spec = Pod::Spec.new { |s| s.dependency 'ASIWebPageRequest' }
+    resolver = Pod::Resolver.new(spec)
+
+    spec.platform = :ios
+    lambda { resolver.resolve }.should.not.raise
+    spec.platform = :osx
+    lambda { resolver.resolve }.should.not.raise
+  end
+
+  it "raises once any of the dependencies does not match the platform of the root spec (Podfile)" do
+    spec = Pod::Spec.new { |s| s.dependency 'ASIWebPageRequest' }
+    resolver = StubbedResolver.new(spec)
+
+    spec.platform = :ios
+    resolver.stub_platform = :ios
+    lambda { resolver.resolve }.should.not.raise
+    resolver.stub_platform = :osx
+    lambda { resolver.resolve }.should.raise Pod::Informative
+
+    spec.platform = :osx
+    resolver.stub_platform = :osx
+    lambda { resolver.resolve }.should.not.raise
+    resolver.stub_platform = :ios
+    lambda { resolver.resolve }.should.raise Pod::Informative
+  end
 end